Control Apparatus

1. A method of forming an airfoil, said method comprising the steps of providing a base having a configuration which is different than the configuration of the airfoil, applying material to the base to form the airfoil, said step of applying material to the base to form the airfoil including the steps of operating a spray means to direct a flow of material toward the base to form on the base a body of sprayed material extending at least part way around the base and having an exterior surface area with a configuration corresponding to the configuration of at least a portion of the airfoil, and removing the base from the body of sprayed material to provide an airfoil having a cavity with a configuration corresponding to the configuration of the base.

2. A method as set forth in claim 1 wherein said step of operating said spray means includes the step of supplying material in a powdered form to said spray means, heating the material, and directing a flow of the heated material toward the base.

3. A method of applying a covering over at least a portion of a workpiece, said method comprising the steps of holding the workpiece with a gripper means, providing a spray means which is selectively operable to direct a flow of material having either a first composition or a second composition toward the workpiece while it is held by said gripper means, operating the spray means to direct a flow of material having the first composition toward the workpiece to form over at least a portion of the workpiece an initial covering having a thickness which is less than a first predetermined thickness and is formed of material having the first composition while the workpiece is held by said gripper means, detecting the thickness of the initial covering while holding the workpiece with said gripper means, operating the spray means to increase the thickness of the initial covering of material having the first composition to the first predetermined thickness while holding the workpiece with the gripper means, operating the spray means to direct a flow of material having the second composition toward the workpiece to form over at least a portion of the initial covering a second covering having a thickness which is less than a second predetermined thickness and is formed of material having the second composition while the workpiece is held by the gripper means, detecting the thickness of the second covering while holding the workpiece with the gripper means, and operating the spray means to increase the thickness of the second covering of material having the second composition to the second predetermined thickness while holding two workpiece with the gripper means.

4. A method as set forth in claim 3 wherein said step of operating the spray means to increase the thickness of the initial covering of material includes the step of increasing the thickness of the initial covering to a thickness which varies from the first predetermined thickness by less than 0.0015 inches, said step of operating the spray means to increase the thickness of the second covering to a thickness which varies from the second predetermined thickness by less than 0.0015 inches.

5. A method as set forth in claim 3 wherein said step of detecting the thickness of the initial covering includes the step of detecting when a surface area of the workpiece is at the focal point of a lens before applying material to the surface of the workpiece with the spray means and, after applying to the workpiece the initial covering having a thickness which is less than the first predetermined thickness, detecting when a surface area on the initial covering is at the focal point of the lens, said step of detecting the thickness of the second covering includes the step of detecting when a surface area on the second covering is at the focal point of the lens prior to performance of said step of operating the spray means to increase the thickness of the second covering.

6. A method as set forth in claim 5 wherein said step of detecting when a surface area of the workpiece is at the focal point of a lens includes the steps of varying the distance between the lens and the surface area of the workpiece through a series of incremental distances, providing a series of data storage locations, storing in the data storage locations data indicative of an amount of light reflected from the surface of the workpiece at a plurality of the incremental distances, said step of storing data including the steps of entering data for each incremental distance in turn into a first data storage location of the series of data storage locations, shifting stored data from each data storage location in the series of data storage locations to a next data storage location in the series of data storage locations and removing the data in a last data storage from the series of data storage locations whenever data is to be enetered into the first data storage location, and comparing the data in the first data storage location with the data in the last data storage location to determine when the data stored in the first data storage location is indicative of an amount of light which is less than the amount of light indicated by the data stored in the last data storage location.

7. A method as set forth in claim 3 wherein said step of operating the spray means to direct a flow of material having the first composition toward the workpiece includes the step of supplying material having the first composition to the spray means in powdered form, heating the material having the first composition, and directing a flow of the heated material having the first composition toward the workpiece, said step of operating the spray means to direct a flow of material having the second composition toward the workpiece including the step of supplying material having the second composition to the spray means in powdered form, heating the material having the second composition and directing a flow of the heated material having the second composition toward the workpiece.

8. A method of applying a covering of a predetermined thickness to at least a portion of a workpiece, said method including the steps of engaging the workpiece with a gripper assembly, applying material to the workpiece by operating a spray means to direct a flow of the material toward the workpiece while it is held by the gripper assembly, said step of operating a spray means includes the steps of supplying material in a powdered form to the spray means, heating the material and directing a flow of the heated material toward the workpiece, effecting relative movement between the spray means and the workpiece during said step of applying material to the workpiece, after applying material to the workpiece to form an initial covering of a thickness which is less than the predetermined thickness, interrupting the application of material to the workpiece, determining the thickness of the initial covering without engaging the initial covering with a solid object, said step of determining the thickness of the initial covering including the step of directing radiant energy against the initial covering while the workpiece is held by the gripper assembly, and increasing the thickness of the initial covering to the predetermined thickness after having determined the thickness of the initial covering by again operating the spray means to direct a flow of the material toward the workpiece while holding the workpiece with the gripper assembly.

9. A method as set forth in claim 7 wherein said step of effecting relative movement between the spray means and the workpiece includes effecting relative movement therebetween through a major portion of a work stroke at a substantially uniform speed.

10. A method of applying a covering over at least a portion of a workpiece, said method comprising the steps of holding the workpiece with a gripper means, providing a spray means which is selectively operable to direct a flow of material having either a first composition, a second composition, or a mixture of the first and second compositions toward the workpiece while it is held by said gripper means, operating the spray means to direct a flow of material having the first composition toward the workpiece to form over at least a portion of the workpiece an initial covering formed of material having the first composition while the workpiece is held by said gripper means, operating the spray means to direct a flow of material having a composition which is a mixture of the first and second materials toward the workpiece to form over at least a portion of the initial covering a transition covering formed of material which is a mixture of the first and second compositions while the workpiece is held by said gripper means, and operating the spray means to direct a flow of material having the second composition toward the workpiece to form over at least a portion of the transition covering a third covering formed of material having the second composition while the workpiece is held by the gripper means, said step of holding the workpiece with the gripper means includes the step of continuously holding the workpiece with the gripper means from a time immediately prior to initiation of operation of the spray means to apply the initial covering at least until completion of application of the third covering.

11. A method as set forth in claim 10 further including the steps of detecting the thickness of the initial covering while holding the workpiece with said gripper means, operating the spray means to increase the thickness of the initial covering until the initial covering has the desired thickness, detecting the thickness of the transition covering while holding the workpiece with said gripper means, operating the spray means to increase the thickness of the transition covering until the transition covering has a desired thickness, detecting the thickness of the third covering while holding the workpiece with said gripper means, and operating the spray to increase the thickness of the third covering until the third covering has a desired thickness.

12. A method as set forth in claim 10 wherein said steps of operating the spray means to form the initial, transition and third coverings of material over the workpiece include the step of forming a combined covering which has a total thickness which varies from a desired thickness by less than 0.0015 inches.

13. A method as set forth in claim 10 further including the step of detecting the thickness of the initial covering by detecting when a surface area of the workpiece is at the focal point of a lens before applying material to the surface of the workpiece with the spray means and detecting when a surface area on the initial covering is at the focal point of the lens with the distance between the lens and the surface area of the workpiece increased by a distance equal to the desired thickness of the initial covering.

14. A method as set forth in claim 10 wherein said step of operating the spray means to direct a flow of material having the first composition toward the workpiece includes the step of supplying material having the first composition to the spray means in powdered form, heating the material having the first composition, and directing a flow of the heated material having the first composition toward the workpiece, said step of operating the spray means to direct a flow of material having a composition which is a mixture of the first and second materials including the step of supplying materials having the first and second compositions to the spray means in powdered form, heating the materials having the first and second compositions and directing a flow of the heated material having the first and second compositions toward the workpiece, said step of operating the spray means to direct a flow of material having the second composition toward the workpiece including the step of supplying material having the second composition to the spray means in powdered form, heating the material having the second composition and directing a flow of the heated material having the second composition toward the workpiece.

15. A method as set forth in claim 10 further including the step of effecting relative movement between the spray means and the workpiece along each of three transversely extending axes and effecting rotational movement between the spray means and the workpiece about each of the transversely extending axes to thereby vary the spatial relationship between the spray means and the workpiece.

16. A method of applying a covering over at least a portion of a workpiece with a spray assembly while the workpiece is held by a gripper, said method comprising the steps of gripping the workpiece with the gripper, supporting the gripper for rotational movement about an axis extending through the workpiece while it is held by the gripper and for pivotal movement in any direction relative to the spray assembly about a pivot point disposed on the axis to enable the orientation of the workpiece relative to the spray assembly to be varied, rotating the gripper and workpiece about the axis which extends through the workpiece to vary the orientation of the workpiece relative to the spray assembly, and pivoting the workpiece about the pivot point to further vary the orientation of the workpiece relative to the spray assembly.

17. A method as set forth in claim 16 wherein said step of pivoting the workpiece about the pivot point includes pivoting the workpiece along a conical plane having its peak at the pivot point.

18. A method as set forth in claim 17 further including the steps of providing a source of light, directing light from the light source against the covering with a lens, reflecting light from the covering back to the light source, increasing the amount of light reflected back to the light source by varying the distance between the lens and the covering in a first direction, subsequently decreasing the amount of light reflected back to the light source by continuing varying the distance between the lens and the covering in the first direction, and detecting when the lens is spaced apart from the covering by a predetermined distance by detecting when the amount of light reflected back to the light source stops increasing and starts decreasing.

19. A method as set forth in claim 18 wherein said step of detecting when the amount of light reflected back to the light source stops increasing and starts decreasing includes the steps of storing data corresponding to the amount of light reflected back to the light source at each of a plurality of distances between the lens and the covering, comparing the stored data for a plurality of distances between the lens and covering, and determining when the stored data indicates that the light reflected back to the light source stops increasing and starts decreasing.

20. A method of applying a covering over at least a portion of a workpiece with a spray assembly while the workpiece is held by a gripper, said method comprising the steps of gripping the workpiece with the gripper, applying a first layer of the covering to the workpiece in longitudinally extending strips by effecting relative movement between the spray assembly and gripper while operating the spray assembly to direct a flow of material toward the workpiece, detecting the thickness of the first layer of the covering, comparing the thickness of the first layer of the covering to a desired thickness, and applying a second layer of the covering to the workpiece in longitudinally extending strips which overlie the strips of the first layer of the covering and have longitudinal central axes which are offset from the longitudinal central axes of the first layer of the covering by effecting relative movement between the spray assembly and gripper while operating the spray assembly to direct a flow of material toward the workpiece, said step of applying a second layer of the covering to the workpiece being continued until the covering has the desired thickness.

21. A method as set forth in claim 20 wherein said step of applying a second layer of the covering to the workpiece includes the step of varying the speed of relative movement between the workpiece and spray assembly to vary the thickness of the strips which overlie the strips of the first layer of the covering.

22. A method as set forth in claim 21 wherein said step of applying a first layer of the covering includes the steps of directing a flow of a first material toward the workpiece from the spray assembly, said step of applying a second layer of the covering includes the step of directing a flow of a second material toward the workpiece from the spray assembly.

23. A method as set forth in claim 20 further including the step of continuously maintaining the gripper in engagement with the workpiece while performing the steps of applying a first layer of the covering, detecting the thickness and applying a second layer of the covering.

24. A method as set forth in claim 23 further including the step of conducting a flow of a cooling fluid through the workpiece while performing said steps of applying a first layer of the covering and applying a second layer of the covering.

25. A method as set forth in claim 20 wherein said step of detecting the thickness of the first layer includes the steps of providing a source of light, directing light from the light source against the first layer with a lens, reflecting light from the first layer back to the light source, increasing the amount of light reflected back to the light source by varying the distance between the lens and the first layer in a first direction, subsequently decreasing the amount of light reflected back to the light source by continuing varying the distance between the lens and the first layer in the first direction, and detecting when the lens is spaced apart from the first layer by a predetermined distance by detecting when the amount of light reflected back to the light source stops increasing and starts decreasing.

26. A method as set forth in claim 25 wherein said step of detecting when the amount of light reflected back to the light source stops increasing and starts decreasing includes the steps of storing data corresponding to the amount of light reflected back to the light source at each of a plurality of distances between the lens and the first layer, comparing the stored data for a plurality of distances between the lens and initial covering, and determining when the stored data indicates that the light reflected back to the light source stops increasing and starts decreasing.

27. A method of applying a covering of material to at least a portion of an airfoil, said method comprising the steps of gripping one end portion of the airfoil with a gripper, supplying material in a powdered form to a spray assembly, directing a flow of the powdered material from the spray assembly toward the airfoil, rotating the gripper and airfoil relative to the spray assembly about a first axis which extends generally parallel to the path of flow of material from the spray assembly to change the orientation of the airfoil relative to the spray assembly, rotating the gripper and airfoil relative to the spray assembly about a second axis which extends transversely to the first axis to change the orientation of the airfoil relative to the spray assembly, and rotating the gripper and airfoil relative to the spray assembly about a third axis which extends transversely to the first and second axes to change the orientation of the airfoil relative to the spray assembly.

28. A method as set forth in claim 27 further including the step of moving the gripper and airfoil relative to the spray assembly along the first axis to change the distance between the airfoil and the spray assembly.

29. A method as set forth in claim 28 further including the step of moving the gripper and airfoil relative to the spray assembly along the second axis to vary the position of the airfoil relative to the path of flow of material from the spray assembly.

30. A method as set forth in claim 27 wherein said step of supplying material in a powdered form to the spray assembly includes the step of supplying material having a first composition, said step of directing a flow of powdered material from the spray assembly toward the airfoil includes directing a flow of the material having a first composition toward the airfoil, said step of supplying material in a powdered form to the spray assembly further includes the step of supplying a material having a second composition, said step of a flow of powdered material from the spray assembly toward the airfoil includes the step of directing a flow of material which is a mixture of the first and second compositions toward the airfoil after having performed said step of directing a flow of material having the first composition toward the airfoil and, thereafter, directing a flow of material which has the second composition toward the airfoil.

31. A method as set forth in claim 30 further including the steps of heating the materials having the first and second compositions before directing the materials toward the airfoil and conducting a flow of cooling fluid through the airfoil while directing the heated materials toward the airfoil.

32. A method as set forth in claim 27 further including the steps of providing a source of light, directing light from the light source against a surface area of the covering with a lens, reflecting light from the surface area to a photosensor, decreasing the amount of light reflected back to the photosensor by effecting relative movement between the lens and the surface area of the covering in one direction, subsequently increasing the amount of light reflected back to the photosensor by continuing to effect relative movement between the lens and the surface area of the covering in the one direction and detecting when the lens is spaced apart from the surface area of the covering by a predetermined distance by detecting when the amount of light reflected back to the photosensor stops decreasing and starts increasing as the distance between the lens and the surface area of the covering is changed in the one direction.

33. A method of applying a covering of a desired thickness to at least a portion of a workpiece, said method comprising the steps of applying to the workpiece an initial covering having a thickness which is less than the desired thickness by operating a spray means to direct a flow of material toward the workpiece, determining the thickness of the initial covering, comparing the thickness of the initial covering with the desired covering thickness to determine the difference between thickness of the initial covering and the desired covering thickness, and increasing the thickness of the covering to the desired thickness by operating the spray means to direct a flow of material toward the initial covering, at least one of the steps of applying an initial covering and increasing the thickness of the covering including the steps of effecting relative movement between the spray means and the workpiece along each of three transversely extending axes and effecting rotational movement between the spray means and the workpiece about each of three transversely extending axes to thereby vary the spatial relationship between the spray means and the workpiece.

34. A method as set forth in claim 33 further including the step of providing a record of the actual thickness of the covering applied to the workpiece.

35. A method as set forth in claim 33 wherein the desired thickness of the covering is different at different locations on the workpiece, said step of applying an initial covering includes the step of applying an initial covering having different thicknesses at different locations on the workpiece, said step of determining the thickness of the initial covering including the steps of determining the thickness of the initial covering at a plurality of locations where the desired covering has different thicknesses, said step of comparing the thickness of the initial covering with the desired thickness of the initial covering includes the step of comparing the thickness of the initial covering at each of the plurality of locations with the desired thickness of the covering at each of the plurality of locations.

36. A method as set forth in claim 33 wherein said step of applying an initial covering includes the step of applying an initial covering of substantially uniform thickness to the workpiece.

37. A method as set forth in claim 33 wherein said step of determining the thickness of the initial covering includes the step of detecting the thickness of the initial covering at each of a plurality of locations on the workpiece, said step of comparing the thickness of the initial covering with the desired thickness includes the steps of comparing the thickness at each of the plurality of locations with the desired thickness at each of the plurality of locations, said step of increasing the thickness of the covering includes the steps of increasing the thickness of the covering at each of the plurality of locations by an amount which corresponds to the difference between the thickness of the initial covering at the location and the desired thickness of the covering at the location.

38. A method as set forth in claim 33 further including the step of removing at least a portion of the workpiece from the covering of sprayed material to provide a cavity within the covering.

39. A method of applying a covering of a desired thickness to at least a portion of a workpiece, said method comprising the steps of applying to the workpiece an initial covering having a thickness which is less than the desired thickness by operating a spray means to direct a flow of material toward the workpiece, determining the thickness of the initial covering, said step of determining the thickness of the initial covering includes the steps of providing a source of light, directing light from the light source against a surface area of the initial covering with a lens, reflecting light from the surface area to a photosensor, decreasing the amount of light reflected back to the photosensor by effecting relative movement between the lens and the surface area of the initial covering in one direction, subsequently increasing the amount of light reflected back to the photosensor by continuing to effect relative movement between the lens and the surface area of the initial covering in the one direction and detecting when the lens is spaced apart from the surface area of the initial covering by a predetermined distance by detecting when the amount of light reflected back to the photosensor stops decreasing and starts increasing as the distance between the lens and the surface area of the initial covering is changed in the one direction, comparing the thickness of the initial covering with the desired covering thickness to determine the difference between thickness of the initial covering and the desired covering thickness, and increasing the thickness of the covering to the desired thickness by operating the spray means to direct a flow of material toward the initial covering.

40. A method of applying a covering of a desired thickness to at least a portion of a workpiece, said method comprising the steps of applying to the workpiece an initial covering having a thickness which is less than the desired thickness by operating a spray means to direct a flow of material toward the workpiece, said step of applying an initial covering to the workpiece includes the steps of applying a plurality of layers of material to the workpiece to form the initial covering, said steps of applying a plurality of layers of material to the workpiece including the steps of applying one of the layers in strips and applying the next succeeding layer in strips having longitudinal axes which are offset from longitudinal axes of the strips of the one layer, determining the thickness of the initial covering, comparing the thickness of the initial covering with the desired covering thickness to determine the difference between thickness of the initial covering and the desired covering thickness, and increasing the thickness of the covering to the desired thickness by operating the spray means to direct a flow of material toward the initial covering.

41. A method as set forth in claim 40 further including the step of providing a record of the actual thickness of the covering applied to the workpiece.

42. A method as set forth in claim 40 wherein the desired thickness of the covering is different at different locations on the workpiece, said step of applying an initial covering further includes the step of applying an initial covering having different thicknesses at different locations on the workpiece, said step of determining the thickness of the initial covering including the steps of determining the thickness of the initial covering at a plurality of locations where the desired covering has different thicknesses, said step of comparing the thickness of the initial covering with the desired thickness of the initial covering includes the step of comparing the thickness of the initial covering at each of the plurality of locations with the desired thickness of the covering at each of the plurality of locations.

43. A method as set forth in claim 40 wherein said step of applying an initial covering includes the step of applying an initial covering of substantially uniform thickness to the workpiece.

44. A method as set forth in claim 40 further including the steps of effecting relative movement between the spray means and the workpiece along each of three transversely extending axes and effecting rotational movement between the spray means and the workpiece about each of three transversely extending axes to thereby vary the spatial relationship between the spray means and the workpiece.

45. A method as set forth in claim 40 wherein said step of determining the thickness of the initial covering includes the step of detecting the thickness of the initial covering at each of a plurality of locations on the workpiece, said step of comparing the thickness of the initial covering with the desired thickness includes the steps of comparing the thickness at each of the plurality of locations with the desired thickness at each of the plurality of locations, said step of increasing the thickness of the covering includes the steps of increasing the thickness of the covering at each of the plurality of locations by an amount which corresponds to the difference between the thickness of the initial covering at the location and the desired thickness of the covering at the location.

46. A method as set forth in claim 40 wherein said step of determining the thickness of the initial covering includes the steps of providing a source of light, directing light from the light source against a surface area of the initial covering with a lens, reflecting light from a surface area to a photosensor, decreasing the amount of light reflected back to the photosensor by effecting relative movement between the lens and the surface area of the initial covering in one direction, subsequently increasing the amount of light reflected back to the photosensor by continuing to effect relative movement between the lens and the surface area of the initial covering in the one direction and detecting when the lens is spaced apart from the surface area of the initial covering by a predetermined distance by detecting when the amount of light reflected back to the photosensor stops decreasing and starts increasing as the distance between the lens and the surface area of the initial covering is changed in the one direction.

47. A method as set forth in claim 40 wherein said step of operating a spray means includes the steps of supplying material in a powdered form to said spray means, heating the material, and directing a flow of the heated material toward the workpiece.

48. A method as set forth in claim 47 wherein the workpiece has an internal passage and the method further includes the step of inducing a flow of fluid through the internal passage while directing the flow of heated material toward the workpiece.

49. A method as set forth in claim 40 including the step of effecting pivotal movement of the workpiece relative to the spray means in any direction about a pivot point to vary the orientation of the workpiece relative to the spray means.

50. A method as set forth in claim 49 further including the step of moving the pivot point along a path extending generally parallel to a path of flow of material from the spray means to vary the distance between the spray means and the workpiece.

51. A method as set forth in claim 40 wherein said step of determining the thickness of the initial covering includes the step of detecting the thickness of the initial covering to within less than 0.0005 inches of the actual thickness of the covering.

52. A method as set forth in claim 40 further including the step of engaging the workpiece with a gripper and continuously maintaining the gripper in engagement with the workpiece while performing said steps of applying an initial covering to the workpiece, determining the thickness of the initial covering and increasing the thickness of the covering.

53. A method as set forth in claim 40 wherein said step of determining the thickness of the initial covering includes the step of utilizing electrical energy from a source of electrical energy to detect the thickness of the initial covering without engaging the initial covering.

54. A method as set forth in claim 40 wherein said step of increasing the thickness of the covering to the desired thickness includes the step of increasing the thickness of the covering until its thickness differs from the desired thickness by less than 0.0015 of an inch.

55. A method as set forth in claim 40 further including the step of removing at least a portion of the workpiece from the covering of the sprayed material to provide a cavity within the covering.

56. A method of applying a covering of a desired thickness to at least a portion of a workpiece having an internal passage, said method comprising the steps of applying to the workpiece an initial covering having a thickness which is less than the desired thickness by operating a spray means to direct a flow of material toward the workpiece, said step of operating a spray means including the steps of supplying material in a powdered form to said spray means, heating the material, and directing a flow of the heated material toward the workpiece, inducing a flow of fluid through the internal passage while directing the flow of heated material toward the workpiece, determining the thickness of the initial covering, comparing the thickness of the initial covering with the desired covering thickness to determine the difference between thickness of the initial covering and the desired covering thickness, and increasing the thickness of the covering to the desired thickness by operating the spray means to direct a flow of material toward the initial covering.

57. A method of applying a covering of a desired thickness to at least a portion of a workpiece, said method comprising the steps of applying to the workpiece an initial covering having a thickness which is less than the desired thickness by operating a spray means to direct a flow of material toward the workpiece, said step of applying an initial covering to the workpiece includes the step of effecting relative movement between the workpiece and spray means and varying the speed of relative movement between the workpiece and spray means to vary the amount of material which is applied over a surface area of the workpiece, determining the thickness of the initial covering, comparing the thickness of the initial covering with the desired covering thickness to determine the difference between thickness of the initial covering and the desired covering thickness, and increasing the thickness of the covering to the desired thickness by operating the spray means to direct a flow of material toward the initial covering.

58. A method as set forth in claim 57 further including the step of providing a record of the actual thickness of the covering applied to the workpiece.

59. A method as set forth in claim 57 wherein the desired thickness of the covering is different at different locations on the workpiece, said step of applying an initial covering includes the step of applying an initial covering having different thicknesses at different locations on the workpiece, said step of determining the thickness of the initial covering including the steps of determining the thickness of the initial covering at a plurality of locations where the desired covering has different thicknesses, said step of comparing the thickness of the initial covering with the desired thickness of the initial covering includes the step of comparing the thickness of the initial covering at each of the plurality of locations with the desired thickness of the covering at each of the plurality of locations.

60. A method as set forth in claim 57 further including the steps of effecting relative movement between the spray means and the workpiece along each of three transversely extending axes and effecting rotational movement between the spray means and the workpiece about each of three transversely extending axes to thereby vary the spatial relationship between the spray means and the workpiece.

61. A method as set forth in claim 57 wherein said step of determining the thickness of the initial covering includes the step of detecting the thickness of the initial covering at each of a plurality of locations on the workpiece, said step of comparing the thickness of the initial covering with the desired thickness includes the steps of comparing the thickness at each of the plurality of locations with the desired thickness at each of the plurality of locations, said step of increasing the thickness of the covering includes the steps of increasing the thickness of the covering at each of the plurality of locations by an amount which corresponds to the difference between the thickness of the initial covering at the location and the desired thickness of the covering at the location.

62. A method as set forth in claim 57 wherein said step of determining the thickness of the initial covering includes the steps of providing a source of light, directing light from the light source against a surface area of the initial covering with a lens, reflecting light from the surface area to a photosensor, decreasing the amount of light reflected back to the photosensor by effecting relative movement between the lens and the surface area of the initial covering in one direction, subsequently increasing the amount of light reflected back to the photosensor by continuing to effect relative movement between the lens and the surface area of the initial covering in the one direction and detecting when the lens is spaced apart from the surface area of the initial covering by a predetermined distance by detecting when the amount of light reflected back to the photosensor stops decreasing and starts increasing as the distance between the lens and the surface area of the initial covering is changed in the one direction.

63. A method as set forth in claim 57 wherein said step of applying an initial covering to the workpiece includes the steps of applying a plurality of layers of material to the workpiece to form the initial covering, said steps of applyling a plurality of layers of material to the workpiece including the steps of applying one of the layers in strips and applying the next succeeding layer in strips having longitudinal axes which are offset from longitudinal axes of the strips of the one layer.

64. A method as set forth in claim 57 wherein said step of operating a spray means includes the steps of supplying material in a powdered form to said spray means, heating the material, and directing a flow of the heated material toward the workpiece.

65. A method as set forth in claim 57 wherein the workpiece has an internal passage and the method further includes the step of inducing a flow of fluid through the internal passage while directing the flow of heated material toward the workpiece.

66. A method as set forth in claim 57 including the step of effecting pivotal movement of the workpiece relative to the spray means in any direction about a pivot point to vary the orientation of the workpiece relative to the spray means.

67. A method as set forth in claim 66 further including the step of moving the pivot point along a path extending generally parallel to a path of flow of material from the spray means to vary the distance between the spray means and the workpiece.

68. A method as set forth in claim 57 wherein said step of determining the thickness of the initial covering includes the step of detecting the thickness of the initial covering to within less than 0.0005 inches of the actual thickness of the covering.

69. A method as set forth in claim 57 further including the step of engaging the workpiece with a gripper and continuously maintaining the gripper in engagement with the workpiece while performing said steps of applying an initial covering to the workpiece, determining the thickness of the initial covering and increasing the thickness of the covering.

70. A method as set forth in claim 57 wherein said step of determining the thickness of the initial covering includes the step of utilizing electrical energy from a source of electrical energy to detect the thickness of the initial covering without engaging the initial covering.

71. A method as set forth in claim 57 wherein said step of applying an initial covering to the workpiece includes the step of applying a plurality of longitudinally extending strips to the workpiece with the strips in an overlapping relationship.

72. A method as set forth in claim 57 wherein said step of increasing the thickness of the covering to the desired thickness includes the step of increasing the thickness of the covering until its thickness differs from the desired thickness by less than 0.0015 of an inch.

73. A method as set forth in claim 57 further including the step of removing at least a portion of the workpiece from the covering of sprayed material to provide a cavity within the covering.

74. A method of applying a covering of a desired thickness to at least a portion of a workpiece, said method comprising the steps of applying to the workpiece an initial covering having a thickness which is less than the desired thickness by operating a spray means to direct a flow of material toward the workpiece, determining the thickness of the initial covering, comparing the thickness of the initial covering with desired covering thickness to determine the difference between thickness of the initial covering and the desired covering thickness, and increasing the thickness of the covering to the desired thickness by operating the spray means to direct a flow of material toward the initial covering, at least one of the steps of applying an initial covering and increasing the thickness of the covering including the step of effecting pivotal movement of the workpiece relative to the spray means in any direction about a pivot point to vary the orientation of the workpiece relative to the spray means.

75. A method as set forth in claim 74 wherein the desired thickness of the covering is different at different locations on the workpiece, said step of applying an initial covering includes the step of applying an initial covering having different thicknesses at different locations on the workpiece, said step of determining the thickness of the initial covering including the steps of determining the thickness of the initial covering at a plurality of locations where the desired covering has different thicknesses, said step of comparing the thickness of the initial covering with the desired thickness of the initial covering includes the step of comparing the thickness of the initial covering at each of the plurality of locations with the desired thickness of the covering at each of the plurality of locations.

76. A method as set forth in claim 74 further including the step of operating a printer to provide a printed record the thickness of the covering at each of the plurality of locations.

77. A method as set forth in claim 74 wherein said step of applying an initial covering includes the step of applying an initial covering of substantially uniform thickness to the workpiece.

78. A method as set forth in claim 74 wherein said step of determining the thickness of the initial covering includes the step of detecting the thickness of the initial covering at each of a plurality of locations on the workpiece, said step of comparing the thickness of the initial covering with the desired thickness includes the steps of comparing the thickness at each of the plurality of locations with the desired thickness at each of the plurality of locations, said step of increasing the thickness of the covering includes the steps of increasing the thickness of the covering at each of the plurality of locations by an amount which corresponds to the difference between the thickness of the initial covering at the location and the desired thickness of the covering at the location.

79. A method as set forth in claim 74 wherein said step of determining the thickness of the initial covering includes the steps of providing a source of light, directing light from the light source against a surface area of the initial covering with a lens, reflecting light from the surface area to a photosensor, decreasing the amount of light reflected back to the photosensor by effecting relative movement between the lens and the surface area of the initial covering in one direction, subsequently increasing the amount of light reflected back to the photosensor by continuing to effect relative movement between the lens and the surface area of the initial covering in the one direction and detecting when the lens is spaced apart from the surface area of the initial covering by a predetermined distance by detecting when the amount of light reflected back to the photosensor stops decreasing and starts increasing as the distance between the lens and the surface area of the initial covering is changed in the one direction.

80. A method as set forth in claim 74 wherein said step of operating a spray means includes the steps of supplying material in a powdered form to said spray means, heating the material, and directing a flow of the heated material toward the workpiece.

81. A method as set forth in claim 80 wherein the workpiece has an internal passage and the method further includes the step of inducing a flow of fluid through the internal passage while directing the flow of heated material toward the workpiece.

82. A method as set forth in claim 74 further including the step of moving the pivot point along a path extending generally parallel to a path of flow of material from the spray means to vary the distance between the spray means and the workpiece.

83. A method as set forth in claim 74 wherein said step of determining the thickness of the initial covering includes the step of detecting the thickness of the initial covering to within less than 0.0005 inches of the actual thickness of the covering.

84. A method as set forth in claim 74 further including the step of engaging the workpiece with a gripper and continuously maintaining the gripper in engagement with the workpiece while performing said steps of applying an initial covering to the workpiece, determining the thickness of the initial covering and increasing the thickness of the covering.

85. A method as set forth in claim 74 wherein said step of determining the thickness of the initial covering includes the step of utilizing electrical energy from a source of electrical energy to detect the thickness of the initial covering without engaging the initial covering.

86. A method as set forth in claim 74 wherein said step of applying an initial covering to the workpiece includes the step of applying a plurality of longitudinally extending strips to the workpiece with the strips in an overlapping relationship.

87. A method as set forth in claim 74 wherein said step of increasing the thickness of the covering to the desired thickness includes the step of increasing the thickness of the covering until its thickness differs from the desired thickness by less than 0.0015 of an inch.

88. A method as set forth in claim 74 further including the step of removing at least a portion of the workpiece from the covering of sprayed material to provide a cavity within the covering.

89. A method of applying a covering of a desired thickness to at least a portion of a workpiece, said method comprising the steps of applying to the workpiece an initial covering having a thickness which is less than the desired thickness by operating a spray means to direct a flow of material toward the workpiece, said step of applying an initial covering to the workpiece includes the step of applying a plurality of longitudinally extending strips to the workpiece with the strips in an overlapping relationship, determining the thickness of the initial covering, comparing the thickness of the initial covering with the desired covering thickness to determine the difference between thickness of the initial covering and the desired covering thickness, and increasing the thickness of the covering to the desired thickness by operating the spray means to direct a flow of material toward the initial covering.

90. A method as set forth in claim 89 further including the step of providing a record of the actual thickness of the covering applied to the workpiece.

91. A method as set forth in claim 89 wherein the desired thickness of the covering is different at different locations on the workpiece, said step of applying an initial covering further includes the step of applying an initial covering having different thicknesses at different locations on the workpiece, said step of determining the thickness of the initial covering including the steps of determining the thickness of the initial covering at a plurality of locations where the desired covering has different thicknesses, said step of comparing the thickness of the initial covering with the desired thickness of the initial covering includes the step of comparing the thickness of the initial covering at each of the plurality of locations with the desired thickness of the covering at each of the plurality of locations.

92. A method as set forth in claim 89 wherein said step of applying an initial covering includes the step of applying an initial covering of substantially uniform thickness to the workpiece.

93. A method as set forth in claim 89 further including the steps of effecting relative movement between the spray means and the workpiece along each of three transversely extending axes and effecting rotational movement between the spray means and the workpiece about each of three transversely extending axes to thereby vary the spatial relationship between the spray means and the workpiece.

94. A method as set forth in claim 89 wherein said step of determining the thickness of the initial covering includes the step of detecting the thickness of the initial covering at each of a plurality of locations on the workpiece, said step of comparing the thickness of the initial covering with the desired thickness includes the steps of comparing the thickness at each of the plurality of locations with the desired thickness at each of the plurality of locations, said step of increasing the thickness of the covering includes the steps of increasing the thickness of the covering at each of the plurality of locations by an amount which corresponds to the difference between the thickness of the initial covering at the location and the desired thickness of the covering at the location.

95. A method as set forth in claim 89 wherein said step of determining the thickness of the initial covering includes the steps of providing a source of light, directing light from the light source against a surface area of the initial covering with a lens, reflecting light from the surface area to a photosensor, decreasing the amount of light reflected back to the photosensor by effecting relative movement between the lens and the surface area of the initial covering in one direction, subsequently increasing the amount of light reflected back to the photosensor by continuing to effect relative movement between the lens and the surface area of the initial covering in the one direction and detecting when the lens is spaced apart from the surface area of the initial covering by a predetermined distance by detecting when the amount of light reflected back to the photosensor stops decreasing and starts increasing as the distance between the lens and the surface area of the initial covering is changed in the one direction.

96. A method as set forth in claim 89 wherein said step of operating a spray means includes the steps of supplying material in a powdered form to said spray means, heating the material, and directing a flow of the heated material toward the workpiece.

97. A method as set forth in claim 96 wherein the workpiece has an internal passage and the method further includes the step of inducing a flow of fluid through the internal passage while directing the flow of heated material toward the workpiece.

98. A method as set forth in claim 89 further including the step of engaging the workpiece with a gripper and continuously maintaining the gripper in engagement with the workpiece while performing said steps of applying an initial covering to the workpiece, determining the thickness of the initial covering and increasing the thickness of the covering.

99. A method as set forth in claim 89 wherein said step of determining the thickness of the initial covering includes the step of utilizing electrical energy from a source of electrical energy to detect the thickness of the initial covering without engaging the initial covering.

100. A method as set forth in claim 89 wherein said step of increasing the thickness of the covering to the desired thickness includes the step of increasing the thickness of the covering until its thickness differs from the desired thickness by less than 0.0015 of an inch.

101. A method as set forth in claim 89 further including the step of removing at least a portion of the workpiece from the covering of sprayed material to provide a cavity within the covering.

102. A method of applying a covering of material over at least a portion of an airfoil, said method comprising the steps of providing an airfoil, operating a spray means to apply to the airfoil a covering having a thickness which differs from a desired thickness by less than 0.0015 of an inch, said step of operating a spray means includes the steps of supplying material in powdered form to the spray means, heating the material, and directing a flow of the heated material toward the airfoil, interrupting operation of the spray means when the thickness of the covering applied to the airfoil is less than the desired thickness, determining the thickness of the covering on the airfoil with an accuracy which is within less than 0.0005 of the actual thickness of the covering, and resuming operating the spray means to increase the thickness of the covering, said step of determining the thickness of the covering on the airfoil includes the steps of providing a light source, directing light from the source of light against a surface area of the airfoil with a lens before applying material to the airfoil with the spray means, increasing the amount of light reflected back to the light source by changing the distance between the lens and the surface area of the airfoil in a first direction from a first distance to a predetermined distance, subsequently decreasing the amount of light reflected back to the light source by changing the distance between the lens and the surface of the airfoil in the first direction from the predetermined distance to a second distance, detecting when the lens is spaced apart from the surface area of the airfoil by the predetermined distance by detecting when the amount of light reflected back to the light source stops increasing and starts decreasing, and determining the position of the airfoil relative to a reference location when the lens is spaced apart from the airfoil by the predetermined distance, after at least partially performing said step of operating the spray means to apply a covering of a desired thickness to the airfoil performing the steps of directing light from the source of light against a surface area of the covering with the lens, increasing the amount of light reflected back to the light source by changing the distance between the lens and the surface area of the covering in the first direction from a first distance to a predetermined distance, subsequently decreasing the amount of light relfected back to the light source by changing the distance between the lens and the surface area of the covering in the first direction from the predetermined distance to a distance which is different than the predetermined distance, detecting when the lens is spaced apart from the surface area of the covering by the predetermined distance by detecting when the amount of light reflected back to the light source stops increasing and starts decreasing, and determining the position of the airfoil relative to the reference location when the lens is spaced apart from the surface area of the covering by the predetermined distance.

103. A method as set forth in claim 102 wherein said step of detecting when the lens spaced apart from the surface of the airfoil by the predetermined distance further including the steps of storing data corresponding to the amount of light reflected back to the light source at each of a plurality of distances between the lens and the surface of the airfoil, comparing the stored data for a plurality of distances between the lens and surface of the airfoil, and determining when the stored data indicates that the light reflected back to the light source stops increasing and starts decreasing.

104. A method of applying a covering of material over at least a portion of an airfoil, said method comprising the steps of providing an airfoil, operating a spray means to apply to the airfoil a covering having a thickness which differs from a desired thickness by less than 0.0015 of an inch, said step of operating a spray means includes the steps of supplying material in powdered form to the spray means, heating the material, and directing a flow of the heated material toward the airfoil, engaging the airfoil with a gripper assembly prior to performing said step of operating a spray means, supporting the airfoil at first location with the gripper assembly during performance of said step of operating a spray means, moving the airfoil to a second location while supporting the airfoil with the gripper assembly, measuring the thickness of the covering applied to the airfoil by the spray means while supporting the airfoil at the second location with the gripper assembly, moving the airfoil back to the first location while supporting the airfoil with the gripper assembly, and resuming the application of material to the airfoil while it is supported at the first location by the gripper assembly.

105. A method as set forth in claim 104 further including the steps of interrupting operation of the spray means when the airfoil is at the first location and the thickness of the covering applied to the airfoil is less than the desired thickness, said step of measuring the thickness of the covering including the step of determining the thickness of the covering on the airfoil with an accuracy which is within less than 0.0005 of the actual thickness of the covering.

106. A method as set forth in claim 104 wherein said step of determining the thickness of the covering includes the steps of determining the thickness of the covering at a plurality of locations on the airfoil.

107. A method as set forth in claim 104 wherein said step measuring the thickness of the covering includes the step of determining when a surface area of the airfoil is at the focal point of a lens.

108. A method as set forth in claim 104 further including the step of effecting relative movement between the airfoil and the spray means to effect the application of the covering to the airfoil in a plurality of strips which extend longitudinally along the airfoil between root and tip end portions of the airfoil, said step of engaging the airfoil with a gripper assembly including the step of engaging the root end portion of the airfoil with the gripper assembly.

109. A method as set forth in claim 104 wherein the airfoil has an internal passage, said method further including the step of inducing a flow of fluid through the internal passage while directing the flow of heated material toward the airfoil to thereby cool the airfoil.

110. A method as set forth in claim 104 wherein said step of measuring the thickness of the covering includes the step of utilizing electrical energy from a source of electrical energy to detect the thickness of the covering applied to the airfoil without engaging the covering with a solid object while the airfoil is supported at the second location by the gripper assembly.

111. A method as set forth in claim 104 further including the steps of effecting relative movement between the spray means and the airfoil along each of three transversely extending axes and effecting rotational movement between the spray means and the airfoil about each of three transversely extending axes to thereby vary the spatial relationship between the spray means and the airfoil while supporting the airfoil at the first location with the gripper assembly.

112. A method as set forth in claim 104 further including the step of effecting pivotal movement of the airfoil relative to the spray means in any direction about a pivot point to vary the orientation of the airfoil relative to the spray means while supporting the airfoil at the first location with the gripper assembly.

113. A method as set forth in claim 112 further including the step of moving the pivot point along a path extending generally parallel to a path of flow of material from the spray means to vary the distance between the spray means and the airfoil while supporting the airfoil at the first location with the gripper assembly.

114. A method as set forth in claim 112 further including the step of effecting relative movement between the airfoil and the spray means while supporting the airfoil at the first location with the gripper assembly to effect the application of the covering to the airfoil by sequentially applying a plurality of layers of material to the airfoil, said step of applying a plurality of layers of material to the airfoil includes the steps of sequentially spraying a plurality of longitudinally extending strips of the material onto the airfoil to form one of the layers and sequentially spraying onto the one layer a plurality of longitudinally extending strips of material to form the next succeeding layer.

115. A method as set forth in claim 104 wherein said step of spraying a plurality of longitudinally extending strips of material onto the one layer includes the steps of spraying the strips onto the one layer with the longitudinal axes of the strips sprayed onto the one layer offset from the longitudinal axes of the strips of material which form the one layer.

116. A method as set forth in claim 115 wherein said steps of spraying longitudinally extending strips includes the steps of spraying strips which extend between root and tip end portions of the airfoil.

117. A method as set forth in claim 104 wherein said step of measuring the thickness of the covering on the airfoil includes the steps of providing a light source, directing light from the source of light against a surface area of the covering with a lens while the airfoil is supported at the second location by the gripper assembly, increasing the amount of light reflected back to the light source by changing the distance between the lens and the surface area of the covering in a first direction from a first distance to a predetermined distance while the airfoil is supported at the second location by the gripper assembly, subsequently decreasing the amount of light reflected back to the light source by changing the distance between the lens and the surface of the covering in the first direction from the predetermined distance to a second distance, while the airfoil is supported at the second location by the gripper assembly, and detecting when the lens is spaced apart from the surface area of the covering by the predetermined distance by detecting when the amount of light reflected back to the light source stops increasing and starts decreasing.

118. A method as set forth in claim 117 wherein said step of detecting when the amount of light reflected back to the light source stops increasing and starts decreasing includes the steps of storing data corresponding to the amount of light reflected back to the light source at each of a plurality of distances between the lens and the covering, comparing the stored data for a plurality of distances between the lens and covering, and determining when the stored data indicates that the light reflected back to the light source stops increasing and starts decreasing.

119. A method as set forth in claim 104 wherein said step of measuring the thickness of the covering on the airfoil includes the steps of providing a source of light, directing light from the light source against a surface area of the covering with a lens while the airfoil is supported at the second location by the gripper assembly, reflecting light from the surface area to a photosensor, decreasing the amount of light reflected back to the photosensor by effecting relative movement between the lens and the surface area of the covering in one direction while the airfoil is supported at the second location by the gripper assembly, subsequent increasing the amount of light reflected back to the photosensor by continuing to effect relative movement between the lens and the surface area of the covering in the one direction, while the airfoil is supported at the second location by the gripper assembly, and detecting when the lens is spaced apart from the surface area of the covering by a predetermined distance by detecting when the amount of light reflected back to the photosensor stops decreasing and starts increasing as the distance between the lens and the surface area of the covering is changed in the one direction.

120. A method as set forth in claim 119 wherein said step of detecting when the amount of light reflected back to the photosensor stops decreasing and starts increasing includes the steps of storing data corresponding to the amount of light reflected back to the photosensor at each of a plurality of distances between the lens and the surface area of the covering, comparing the stored data for a plurality of distances between the lens and surface area of the covering, and determining when the stored data indicates that the light reflected back to the photosensor stops decreasing and starts increasing.

121. A method of applying a covering of material over at least a portion of an airfoil, said method comprising the steps of providing an airfoil, operating a spray means to apply to the airfoil a covering having a thickness which differs from a desired thickness by less than 0.0015 of an inch, said step of operating a spray means includes the steps of supplying material in powdered form to the spray means, heating the material, and directing a flow of the heated material toward the airfoil, determining the thickness of the covering of material applied to the airfoil, said step of determining the thickness of the covering on the airfoil including the steps of locating the airfoil at a measuring station with a surface area on the airfoil at a predetermined position before applying material to the airfoil with said spray means, and, after applying at least a portion of the covering to the airfoil, locating the airfoil at the measuring station with a surface area on the covering at the predetermined position.

122. A method as set forth in claim 121 wherein said step determining the thickness of the covering on the airfoil includes determining the thickness of the covering on the airfoil with an accuracy which is within less than 0.0005 of the actual thickness of the covering.

123. A method as set forth in claim 121 wherein said step of determining the thickness of the covering includes the steps of determining the thickness of the covering at a plurality of locations on the airfoil.

124. A method as set forth in claim 123 further including the step of operating a printer to provide a printed record of the thickness of the covering at each of the plurality of locations on the airfoil.

125. A method as set forth in claim 121 wherein said step of locating the airfoil at the measuring station with a surface area on the airfoil at a predetermined position before applying material to the airfoil includes the steps of providing a light source, directing light from the source of light against a surface area of the airfoil with a lens, increasing the amount of light reflected back to the light source by changing the distance between the lens and the surface area of the airfoil in a first direction from a first distance to a predetermined distance, subsequently decreasing the amount of light reflected back to the light source by changing the distance between the lens and the surface of the airfoil in the first direction from the predetermined distance to a second distance, detecting when the lens is spaced apart from the surface area of the airfoil by the predetermined distance by detecting when the amount of light reflected back to the light source stops increasing and starts decreasing, and determining the position of the airfoil relative to a reference location when the lens is spaced apart from the airfoil by the predetermined distance, said step of locating the airfoil at the measuring station with a surface area of the covering at the predetermined position after at least partially performing said step of operating the spray means to apply a covering to the airfoil including the steps of directing light from the source of light against a surface area of the covering with the lens, increasing the amount of light reflected back to the light source by changing the distance between the lens and the surface area of the covering in the first direction from a first distance to a predetermined distance, subsequently decreasing the amount of light reflected back to the light source by changing the distance between the lens and the surface area of the covering in the first direction from the predetermined distance to a distance which is different than the predetermined distance, detecting when the lens is spaced apart from the surface area of the covering by the predetermined distance by detecting when the amount of light reflected back to the light source stops increasing and starts decreasing, and determining the position of the airfoil relative to the reference location when the lens is spaced apart from the surface area of the covering by the predetermined distance.

126. A method as set forth in claim 121 wherein said step of locating the airfoil at the measuring station with a surface area on the airfoil at a predetermined position includes the step of determining when the surface area of the airfoil is at the focal point of a lens, said step of locating the airfoil at the measuring station with a surface area on the covering at the predetermined position includes the step of determining when the surface area on the covering is at the focal point of the lens.

127. A method as set forth in claim 121 wherein said step of operating the spray means to apply a covering to the airfoil is performed while the airfoil is disposed at a location spaced apart from the measuring location.

128. A method as set forth in claim 121 further including the step of effecting relative movement between the airfoil and the spray means to effect the application of the covering to the airfoil in a plurality of longitudinally extending strips.

129. A method as set forth in claim 121 wherein the airfoil has an internal passage, said method further including the step of inducing a flow of fluid through the internal passage while directing the flow of heated material toward the airfoil to thereby cool the airfoil.

130. A method as set forth in claim 121 wherein said step of locating the airfoil at the measuring station after applying at least a portion of the covering to the airfoil includes the step of utilizing electrical energy from a source of electrical energy to detect the thickness of the covering applied to the airfoil without engaging the covering with a solid object.

131. A method as set forth in claim 121 further including the steps of effecting relative movement between the spray means and the airfoil along each of three transversely extending axes and effecting rotational movement between the spray means and the airfoil about each of three transversely extending axes to thereby vary the spatial relationship between the spray means and the airfoil.

132. A method as set forth in claim 121 further including the step of effecting pivotal movement of the airfoil relative to the spray means in any direction about a pivot point to vary the orientation of the airfoil relative to the spray means.

133. A method as set forth in claim 121 further including the step of moving the pivot point along a path extending generally parallel to a path of flow of material from the spray means to vary the distance between the spray means and the airfoil.

134. A method as set forth in claim 121 further including the step of effecting relative movement between the airfoil and the spray means to effect the application of the covering to the airfoil by sequentially applying a plurality of layers of material to the airfoil, said step of applying a plurality of layers of material to the airfoil includes the steps of sequentially spraying a plurality of longitudinally extending strips of the material onto the airfoil to form one of the layers and sequentially onto the one layer a plurality of longitudinally extending strips of material to form the next succeeding layer.

135. A method as set forth in claim 134 wherein said step of spraying a plurality of longitudinally extending strips of material onto the one layer includes the steps of spraying the strips onto the one layer with the longitudinal axes of the strips sprayed onto the one layer offset from the longitudinal axes of the strips of material which form the one layer.

136. A method as set forth in claim 134 wherein said steps of spraying longitudinally extending strips includes the steps of spraying strips which extend between root and tip end portions of the airfoil.

137. A method of applying a covering of material over at least a portion of an airfoil, said method comprising the steps of providing an airfoil, operating a spray means to apply to the airfoil a covering having a thickness which differs from a desired thickness by less than 0.0015 of an inch, said step of operating a spray means includes the steps of supplying material in powdered form to the spray means, heating the material, and directing a flow of the heated material toward the airfoil, effecting relative movement between the airfoil and the spray means to effect the application of the covering to the airfoil in a plurality of longitudinally extending strips.

138. A method as set forth in claim 137 further including the steps of interrupting operation of the spray means when the thickness of the covering applied to the airfoil is less than the desired thickness, determining the thickness of the covering on the airfoil with an accuracy which is within less than 0.0005 of the actual thickness of the covering, and resuming operating the spray means to increase the thickness of the covering.

139. A method as set forth in claim 138 wherein said step of determining the thickness of the covering includes the steps of determining the thickness of the covering at a plurality of locations of the airfoil.

140. A method as set forth in claim 139 further including the step of operating a printer to provide a printed record of the thickness of the covering at each of the plurality of locations on the airfoil.

141. A method as set forth in claim 137 wherein said step of determining the thickness of the covering on the airfoil includes the steps of providing a light source, directing light from the source of light against a surface area of the airfoil with a lens before applying material to the airfoil with the spray means, increasing the amount of light reflected back to the light source by changing the distance between the lens and the surface area of the airfoil in a first direction from a first distance to a predetermined distance, subsequently decreasing the amount of light reflected back to the light source by changing the distance between the lens and the surface of the airfoil in the first direction from the predetermined distance to a second distance, detecting when the lens is spaced apart from the surface area of the airfoil by the predetermined distance by detecting when the amount of light reflected back to the light source stops increasing and starts decreasing, and determining the position of the airfoil relative to a reference location when the lens is spaced apart from the airfoil by the predetermined distance, after at least partially performing said step of operating the spray means to apply a covering to the airfoil performing the steps of directing light from the source of light against a surface area of the covering with the lens, increasing the amount of light reflected back to the light source by changing the distance between the lens and the surface area of the covering in the first direction from a first distance to a predetermined distance, subsequently decreasing the amount of light reflected back to the light source by changing the distance between the lens and the surface area of the covering in the first direction from the predetermined distance to a distance which is different than the predetermined distance, detecting when the lens is spaced apart from the surface area of the covering by the predetermined distance by detecting when the amount of light reflected back to the light source stops increasing and starts decreasing, and determining the position of the airfoil relative to the reference location when the lens is spaced apart from the surface area of the covering by the predetermined distance.

142. A method as set forth in claim 137 further including the steps of engaging the airfoil with a gripper assembly prior to performing said step of operating a spray means, supporting the airfoil at first location with the gripper assembly during performance of said step of operating a spray means, moving the airfoil to a second location while supporting the airfoil with the gripper assembly, measuring the thickness of the covering applied to the airfoil by the spray means while supporting the airfoil at the second location with the gripper assembly, moving the airfoil back to the first location while supporting the airfoil with the gripper assembly, and resuming the application of material to the airfoil while it is supported at the first location by the gripper assembly.

143. A method as set forth in claim 137 further including the step of determining the thickness of the covering of material applied to the airfoil, said step of determining the thickness of the covering on the airfoil including the steps of locating the airfoil at a measuring station with a surface area on the airfoil at a predetermined position before applying material to the airfoil with said spray means, and, after applying at least a portion of the covering to the airfoil, locating the airfoil at the measuring station with a surface area on the covering at the predetermined position.

144. A method as set forth in claim 143 wherein said step of locating the airfoil at the measuring station with a surface area on the airfoil at a predetermined position includes the step of determining when the surface area of the airfoil is at the focal point of a lens, said step of locating the airfoil at the measuring station with a surface area on the covering at the predetermined position includes the step of determining when the surface area on the covering is at the focal point of the lens.

145. A method as set forth in claim 143 wherein said step of operating the spray means to apply a covering to the airfoil is performed while the airfoil is disposed at a location spaced apart from the measuring location.

146. A method as set forth in claim 137 wherein the airfoil has an internal passage, said method further including the step of inducing a flow of fluid through the internal passage while directing the flow of heated material toward the airfoil to thereby cool the airfoil.

147. A method as set forth in claim 137 further including the step of utilizing electrical energy from a source of electrical energy to detect the thickness of the covering applied to the airfoil without engaging the covering with a solid object.

148. A method as set forth in claim 137 further including the steps of effecting relative movement between the spray means and the airfoil along each of three transversely extending axes and effecting rotational movement between the spray means and the airfoil about each of three transversely extending axes to thereby vary the spatial relationship between the spray means and the airfoil.

149. A method as set forth in claim 137 further including the step of effecting pivotal movement of the airfoil relative to the spray means in any direction about a pivot point to vary the orientation of the airfoil relative to the spray means.

150. A method as set forth in claim 149 further including the step of moving the pivot point along a path extending generally parallel to a path of flow of material from the spray means to vary the distance between the spray means and the airfoil.

151. A method as set forth in claim 137 wherein said step of effecting relative movement between the airfoil and the spray means to effect the application of the covering to the airfoil further includes the step of sequentially applying a plurality of layers of material to the airfoil, said step of applying a plurality of layers of material to the airfoil includes the steps of sequentially spraying the plurality of longitudinally extending strips of the material onto the airfoil to form one of the layers and sequentially spraying onto the one layer a plurality of longitudinally extending strips of material to form the next succeeding layer.

152. A method as set forth in claim 151 wherein said step of spraying a plurality of longitudinally extending strips of material onto the one layer includes the steps of spraying the strips onto the one layer with the longitudinal axes of the strips sprayed onto the one layer offset from the longitudinal axes of the strips of material which form the one layer.

153. A method as set forth in claim 151 wherein said steps of spraying longitudinally extending strips includes the steps of spraying strips which extend between root and tip end portions of the airfoil.

154. A method as set forth in claim 137 further including the steps of engaging the airfoil with a gripper assembly prior to performing said step of operating a spray means, supporting the airfoil with the gripper assembly during performance of said step of operating a spray means, and measuring the thickness of the covering applied to the airfoil by the spray means while supporting the airfoil with the gripper assembly.

155. A method of applying a covering of material over at least a portion of an airfoil having an internal passage, said method comprising the steps of providing an airfoil operating a spray means to apply to the airfoil a covering having a thickness which differs from a desired thickness by less than 0.0015 of an inch, said step of operating a spray means includes the steps of supplying material in powdered form to the spray means, heating the material, and directing a flow of the heated material toward the airfoil, and inducing a flow of fluid through the internal passage while directing the heated material toward the airfoil to thereby cool the airfoil.

156. A method as set forth in claim 155 further including the steps of interrupting operation of the spray means when the thickness of the covering applied to the airfoil is less than the desired thickness, determining the thickness of the covering on the airfoil with an accuracy which is within less than 0.005 of the actual thickness of the covering, and resuming operating the spray means to increase the thickness of the covering.

157. A method as set forth in claim 156 wherein said step of determining the thickness of the covering includes the steps of determining the thickness of the covering at a plurality of locations on the airfoil.

158. A method as set forth in claim 156 wherein said step of determining the thickness of the covering on the airfoil includes the steps of providing a light source, directing light from the source of light against a surface area of the airfoil with a lens before applying material to the airfoil with the spray means, increasing the amount of light reflected back to the light source by changing the distance between the lens and the surface area of the airfoil in a first direction from a first distance to a predetermined distance, subsequently decreasing the amount of light reflected back to the light source by changing the distance between the lens and the surface of the airfoil in the first direction from the predetermined distance to a second distance, detecting when the lens is spaced apart from the surface area of the airfoil by the predetermined distance by detecting when the amount of light reflected back to the light source stops increasing and starts decreasing, and determining the position of the airfoil relative to a reference location when the lens is spaced apart from the airfoil by the predetermined distance, after at least partially performing said step of operating the spray means to apply a covering to the airfoil performing the steps of directing light from the source of light against a surface area of the covering with the lens, increasing the amount of light reflected back to the light source by changing the distance between the lens and the surface area of the covering in the first direction from a first distance to a predetermined distance, subsequently decreasing the amount of light reflected back to the light source by changing the distance between the lens and the surface area of the covering in the first direction from the predetermined distance to a distance which is different than the predetermined distance, detecting when the lens is spaced apart from the surface area of the covering by the predetermined distance by detecting when the amount of light reflected back to the light source stops increasing and starts decreasing, and determining the position of the airfoil relative to the reference location when the lens is spaced apart from the surface area of the covering by the predetermined distance.

159. A method as set forth in claim 155 further including the step of utilizing electrical energy from a source of electrical energy to detect the thickness of the covering applied to the airfoil without engaging the covering with a solid object.

160. A method as set forth in claim 155 further including the steps of effecting relative movement between the spray means and the airfoil along each of three transversely extending axes and effecting rotational movement between the spray means and the airfoil about each of three transversely extending axes to thereby vary the spatial relationship between the spray means and the airfoil.

161. A method as set forth in claim 155 further including the step of effecting pivotal movement of the airfoil relative to the spray means in any direction about a pivot point to vary the orientation of the airfoil relative to the spray means.

162. A method as set forth in claim 161 further including the step of moving the pivot point along a path extending generally parallel to a path of flow of material from the spray means to vary the distance between the spray means and the airfoil.

163. A method as set forth in claim 155 further including the step of effecting relative movement between the airfoil and the spray means to effect the application of the covering to the airfoil by sequentially applying a plurality of layers of material to the airfoil, said step of applying a plurality of layers of material to the airfoil includes the steps of sequentially spraying a plurality of longitudinally extending strips of the material onto the airfoil to form one of the layers and sequentially spraying onto the one layer a plurality of longitudinally extending strips of material to form the next succeeding layer.

164. A method as set forth in claim 163 wherein said step of spraying a plurality of longitudinally extending strips of material onto the one layer includes the steps of spraying the strips onto the one layer with the longitudinal axes of the strips sprayed onto the one layer offset from the longitudinal axes of the strips of material which form the one layer.

165. A method as set forth in claim 163 wherein said steps of spraying longitudinally extending strips includes the steps of spraying strips which extend between root and tip end portions of the airfoil.

166. A method as set forth in claim 155 further including the steps of engaging the airfoil with a gripper assembly prior to performing said step of operating a spray means, supporting the airfoil with the gripper assembly during performance of said steps of operating a spray means and inducing a flow of fluid through the internal passage, measuring the thickness of the covering applied to the airfoil by the spray means while supporting the airfoild location with the gripper assembly.

167. A method of applying a covering of material over at least a portion of an airfoil, said method comprising the steps of providing an airfoil, operating a spray means to apply to the airfoil a covering having a thickness which differs from a desired thickness by less than 0.0015 of an inch, said step of operating a spray means includes the steps of supplying material in powdered form to the spray means, heating the material, and directing a flow of the heated material toward the airfoil, and utilizing electrical energy from a source of electrical energy to detect the thickness of the covering applied to the airfoil without engaging the covering with a solid object.

168. A method as set forth in claim 169 wherein said step of utilizing electrical energy to detect the thickness of the covering includes the step of detecting the thickness of the covering on the airfoil with an accuracy which is within less than 0.0005 of the actual thickness of the covering.

169. A method as set forth in claim 168 wherein said step of detecting the thickness of the covering includes the steps of detecting the thickness of the covering at a plurality of locations on the airfoil.

170. A method as set forth in claim 169 further including the step of operating a printer to provide a printed record of the thickness of the covering at each of the plurality of locations on the airfoil.

171. A method as set forth in claim 167 wherein said step of utilizing electrical energy to detect the thickness of the covering on the airfoil includes the steps of providing a light source, directing light from the source of light against a surface area of the airfoil with a lens before applying material to the airfoil with the spray means, increasing the amount of light reflected back to the light source by changing the distance between the lens and the surface area of the airfoil in a first direction from a first distance to a predetermined distance, subsequently decreasing the amount of light reflected back to the light source by changing the distance between the lens and the surface of the airfoil in the first direction from the predetermined distance to a second distance, detecting when the lens is spaced apart from the surface area of the airfoil by the predetermined distance by detecting when the amount of light reflected back to the light source stops increasing and starts decreasing, and determining the position of the airfoil relative to a reference location when the lens is spaced apart from the airfoil by the predetermined distance, after at least partially performing said step of operating the spray means to apply a covering to the airfoil, performing the steps of directing light from the source of light against a surface area of the covering with the lens, increasing the amount of light reflected back to the light source by changing the distance between the lens and the surface area of the covering in the first direction from a first distance to a predetermined distance, subsequently decreasing the amount of light reflected back to the light source by changing the distance between the lens and the surface area of the covering in the first direction from the predetermined distance to a distance which is different than the predetermined distance, detecting when the lens is spaced apart from the surface area of the covering by the predetermined distance by detecting when the amount of light reflected back to the light source stops increasing and starts decreasing, and determining the position of the airfoil relative to the reference location when the lens is spaced apart from the surface area of the covering by the predetermined distance.

172. A method as set forth in claim 167 further including the steps of engaging the airfoil with a gripper assembly prior to performing said step of operating a spray means, and supporting the airfoil with the gripper assembly during performance of said step of operating a spray means, said step of utilizing electrical energy to detect the thickness of the covering applied to the airfoil bing performed while supporting the airfoil with the gripper assembly.

173. A method as set forth in claim 169 further including the steps of effecting relative movement between the spray means and the airfoil along each of three transversely extending axes and effecting rotational movement between the spray means and the airfoil about each of three transversely extending axes to thereby vary the spatial relationship between the spray means and the airfoil.

174. A method as set forth in claim 167 further including the step of effecting pivotal movement of the airfoil relative to the spray means in any direction about a pivot point to vary the orientation of the airfoil relative to the spray means.

175. A method as set forth in claim 174 further including the step of moving the pivot point along a path extending generally parallel to a path of flow of material from the spray means to vary the distance between the spray means and the airfoil.

176. A method as set forth in claim 167 further including the step of effecting relative movement between the airfoil and the spray means to effect the application of the covering to the airfoil by sequentially applying a plurality of layers of material to the airfoil, said step of applying a plurality of layers of material to the airfoil includes the steps of sequentially spraying a plurality of longitudinally extending strips of the material onto the airfoil to form one of the layers and sequentially spraying onto the one layer a plurality of longitudinally extending strips of material to form the next succeeding layer.

177. A method as set forth in claim 176 wherein said step of spraying a plurality of longitudinally extending strips of material onto the one layer includes the steps of spraying the strips onto the one layer with the longitudinal axes of the strips sprayed onto the one layer offset from the longitudinal axes of the strips of material which form the one layer.

178. A method as set forth in claim 176 wherein said steps of spraying longitudinally extending strips includes the steps of spraying strips which extend between root and tip end portions of the airfoil.

179. A method as set forth in claim 167 wherein said step of utilizing electrical energy to detect the thickness of the covering includes the step of determining when a surface area of the covering is at the focal point of a lens.

180. A method as set forth in claim 167 wherein said step of utilizing electrical energy to detect the thickness of the covering includes the steps of providing a source of light, directing light from the light source against a surface area of the covering with a lens, reflecting light from the surface area to a photosensor, decreasing the amount of light reflected back to the photosensor by effecting relative movement between the lens and the surface area of the covering in one direction, subsequently increasing the amount of light reflected back to the photosensor by continuing to effect relative movement between the lens and the surface area of the covering in the one direction and detecting when the lens is spaced apart from the surface area of the covering by a predetermined distance by detecting when the amount of light reflected back to the photosensor stops decreasing and starts increasing as the distance between the lens and the surface area of the covering is changed in the one direction.

181. A method as set forth in claim 180 wherein said step of detecting when the amount of light reflected back to the photosensor stops decreasing and starts increasing includes the steps of storing data corresponding to the amount of light reflected back to the photosensor at each of a plurality of distances between the lens and the covering, comparing the stored data for a plurality of distances between the lens and covering, and determining when the stored data indicates that the light reflected back to the photosensor stops decreasing and starts increasing.

182. A method as set forth in claim 167 wherein said step of utilizing electrical energy to detect the thickness of the covering includes the steps of providing a source of light, directing light from the light source against a surface area of the covering with a lens, reflecting light from the surface area to the source of light, increasing the amount of light reflected back to the source of light by effecting relative movement between the lens and the surface area of the covering in one direction, subsequently decreasing the amount of light reflected back to the source of light by continuing to effect relative movement between the lens and the surface area of the covering in the one direction and detecting when the lens is spaced apart from the surface area of the covering by a predetermined distance by detecting when the amount of light reflected back to the source of light stops increasing and starts decreasing as the distance between the lens and the surface area of the covering is changed in the one direction.

183. A method as set forth in claim 182 wherein said step of detecting when the amount of light reflected back to the source of light stops increasing and starts decrasing includes the steps of storing data corresponding to the amount of light reflected back to the source of light at each of a plurality of distances between the lens and the covering, comparing the stored data for a plurality of distances between the lens and covering, and determining when the stored data indicates that the light reflected back to the source of light stops increasing and starts decreasing.

184. A method of applying a covering of material over at least a portion of an airfoil, said method comprising the steps of providing an airfoil, operating a spray means to apply to the airfoil a covering having a thickness which differs from a desired thickness by less than 0.0015 of an inch, said step of operating a spray means includes the steps of supplying material in powdered form to the spray means, heating the material, and directing a flow of the heated material toward the airfoil, effecting relative movement between the spray means and the airfoil along each of three transversely extending axes, and effecting rotational movement between the spray means and the airfoil about each of three transversely extending axes to thereby vary the spatial relationship between the spray means and the airfoil.

185. A method as set forth in claim 184 further including the steps of interrupting operation of the spray means when the thickness of the covering applied to the airfoil is less than the desired thickness, determining the thickness of the covering on the airfoil with an accuracy which is within less than 0.0005 of the actual thickness of the covering, and resuming operating the spray means to increase the thickness of the covering.

186. A method as set forth in claim 185 wherein said step of determining the thickness of the covering includes the steps of determining the thickness of the covering at a plurality of locations on the airfoil.

187. A method of applying a covering of material over at least a portion of an airfoil, said method comprising the steps of providing an airfoil, operating a spray means to apply to the airfoil a covering having a thickness which differs from a desired thickness by less than 0.0015 of an inch, said step of operating a spray means includes the steps of supplying material in powdered form to the spray means, heating the material, and directing a flow of the heated material toward the airfoil, and effecting pivotal movement of the airfoil relative to the spray means in any direction about a pivot point to vary the orientation of the airfoil relative to the spray means.

188. A method as set forth in claim 187 further including the step of moving the pivot point along a path extending generally parallel to a path of flow of material from the spray means to vary the distance between the spray means and the airfoil.

189. A method as set forth in claim 187 further including the steps of interrupting operation of the spray means when the thickness of the covering applied to the airfoil is less than the desired thickness, determining the thickness of the covering on the airfoil with an accuracy which is within less than 0.0005 of the actual thickness of the covering, and resuming operating the spray means to increase the thickness of the covering.

190. A method as set forth in claim 187 wherein said step of determining the thickness of the covering includes the steps of determining the thickness of the covering at a plurality of locations on the airfoil.

191. A method of applying a covering of material over at least a portion of an airfoil, said method comprising the steps of providing an airfoil, operating a spray means to apply to the airfoil a covering having a thickness which differs from a desired thickness by less than 0.0015 of an inch, said step of operating a spray means includes the steps of supplying material in powdered form to the spray means, heating the material, and directing a flow of the heated material toward the airfoil, and effecting relative movement between the airfoil and the spray means to effect the application of the covering to the airfoil by sequentially applying a plurality of layers of material to the airfoil, said step of applying a plurality of layers of material to the airfoil includes the steps of sequentially spraying a plurality of longitudinally extending strips of the material onto the airfoil to form one of the layers and sequentially spraying onto the one layer a plurality of longitudinally extending strips of material to form the next succeeding layer.

192. A method as set forth in claim 191 wherein said step of spraying a plurality of longitudinally extending strips of material onto the one layer includes the steps of spraying the strips onto the one layer with the longitudinal axes of the strips sprayed onto the one layer offset from the longitudinal axes of the strips of material which form the one layer.

193. A method as set forth in claim 191 wherein said steps of spraying longitudinally extending strips includes the steps of spraying strips which extend between root and tip end portions of the airfoil.

194. A method as set forth in claim 191 further including the steps of effecting relative movement between the spray means and the airfoil along each of three transversely extending axes and effecting rotational movement between the spray means and the airfoil about each of three transversely extending axes to thereby vary the spatial relationship between the spray means and the airfoil.

195. A method as set forth in claim 191 further including the step of effecting pivotal movement of the airfoil relative to the spray means in any direction about a pivot point to vary the orientation of the airfoil relative to the spray means.

196. A method as set forth in claim 195 further including the step of moving the pivot point along a path extending generally parallel to a path of flow of material from the spray means to vary the distance between the spray means and the airfoil.

197. A method as set forth in claim 191 further including the steps of interrupting operation of the spray means when the thickness of the covering applied to the airfoil is less than the desired thickness, determining the thickness of the covering on the airfoil with an accuracy which is within less than 0.0005 of the actual thickness of the covering, and resuming operating the spray means to increase the thickness of the covering.

198. A method as set forth in claim 197 wherein said step of determining the thickness of the covering includes the steps of determining the thickness of the covering at a plurality of locations on the airfoil.

199. A method as set forth in claim 191 wherein said step of spraying a plurality of longitudinally extending strips of material onto the one layer includes the steps of spraying the strips onto the one layer with the longitudinal axes of the strips sprayed onto the one layer offset from the longitudinal axes of the strips of material which form the one layer.

200. A method as set forth in claim 199 wherein said steps of spraying longitudinally extending strips includes the steps of spraying strips which extend between root and tip end portions of the airfoil.

201. A method of applying a covering of a desired thickness to at least a portion of a workpiece, said method comprising the steps of applying to the workpiece an initial covering having a thickness which is less than the desired thickness by operating a spray means to direct a flow of material toward the workpiece, determining the thickness of the initial covering, wherein said step of determining the thickness of the intial covering includes the steps of providing a source of light, directing light from the light source against the initial covering with a lens, reflecting light from the initial covering back to the light source, increasing the amount of light reflected back to the light source by varying the distance between the lens and the initial covering in a first direction, subsequently decreasing the amount of light reflected back to the light source by continuing varying the distance between the lens and the initial covering in the first direction, and detecting when the lens is spaced apart from the initial covering by a predetermined distance by detecting when the amount of light reflected back to the light source stops increasing and starts decreasing, comparing the thickness of the initial covering with the desired covering thickness to determine the difference between thickness of the initial covering and the desired covering thickness, and increasing the thickness of the covering to the desired thickness by operating the spray means to direct a flow of material toward the initial covering.

202. A method as set forth in claim 201 wherein said step of detecting when the amount of light reflected back to the light source stops increasing and starts decreasing includes the steps of storing data corresponding to the amount of light reflected back to the light source at each of a plurality of distances between the lens and the initial covering, comparing the stored data for a plurality of distances between the lens and initial covering, and determining when the stored data indicates that the light reflected back to the light source stops increasing and starts decreasing.

203. A method as set forth in claim 202 wherein said step of varying the distance between the lens and the initial covering includes the step of varying the distance through a series of incremental distances, said step of detecting when the amount of light reflected back to the light source stops increasing and starts decreasing includes the steps of providing a series of data storage locations, storing in the data storage locations data indicative of the amount of reflect light at a plurality of the incremental distances, said step of storing data including the steps of entering data for each incremental distance in turn into a first data storage location of the series of data storage locations, shifting stored data from each storage location in the series of daa storage locations to a next data storage location in the series of data storage locations and removing the data in a last data storage from the series of data storage locations whenever data is to be entered into the first data storage location, and comparing the data in the first data storage location with the data in the last data storage location to determine when the data stored in the first data storage location is indicative of an amount of light reflected back to the source which is less than the amount of light indicated by the data stored in the last data storage location.

204. A method of applying a covering of a desired thickness to at least a portion of a workpiece, said method comprising the steps of applying to the workpiece an initial covering having a thickness which is less than the desired thickness by operating a spray means to direct a flow of material toward the workpiece, determining the thickness of the initial covering, said step of determining the thickness of the initial covering includes the steps of providing a source of light, directing light from the light source against a surface area of the initial covering with a lens, reflecting light from the surface area to a photosensor, decreasing the amount of light reflected back to the photosensor by effecting relative movement between the lens and the surface area of the initial covering in one direction, subsequently increasing the amount of light reflected back to the photosensor by continuing to effect relative movement between the lens and the surface area of the intial covering in the one direction and detecting when the lens is spaced apart from the surface area of the initial covering by a predetermined distance by detecting when the amount of light reflected back to the photosensor stops decreasing and starts increasing as the distance between the lens and the surface area of the initial covering is changed in the one direction, comparing the thickness of the initial covering with the desired covering thickness to determine the difference between thickness of the initial covering and the desired covering thickness, and increasing the thickness of the covering to the desired thickness by operating the spray means to direct a flow of material toward the initial covering.

205. A method comprising the steps of providing a workpiece, gripping the workpiece with a gripper assembly, operating a spray means to apply a covering over at least a portion of the workpiece while the workpiece is gripped by the gripper assembly, effecting relative movement between the spray means and the workpiece by moving the gripper assembly relative to the spray means while gripping the workpiece with the gripper assembly, measuring the thickness of the covering applied to the workpiece by the spray means while gripping the workpiece with the gripper assembly, resuming the application of material to the workpiece by operating the spray means after having performed said step of measuring the thickness of the covering and while gripping the workpiece with the gripper assembly, and continuously maintaining a grip on the workpiece with the gripper assembly from the time at which said step of operating a spray means is initiated at least until completion of said step of resuming the application of material to the workpiece.

206. A method as set forth in claim 205 wherein said step measuring the thickness of the covering includes the step of determining when a surface area of the workpiece is at the focal point of a lens, said step of determining when a surface area of the workpiece is at the focal point of the lens being performed while the workpiece is gripped by the workpiece and prior to operation of said spray means to apply a covering over the workpiece.

207. A method as set forth in claim 205 wherein said step of measuring the thickness of the covering includes the step of utilizing electrical energy from a source of electrical energy to detect the thickness of the covering applied to the workpiece without engaging the covering with a solid object.

208. A method as set forth in claim 205 wherein said step of measuring the thickness of the covering on the workpiece includes the steps of providing a light source, directing the light from the source of light against a surface area of the covering with a lens while the workpiece is gripped by the gripper assembly, increasing the amount of light reflected back to the light source by changing the distance between the lens and the surface area of the covering in a first direction from a first distance to a predetermined distance while the workpiece is gripped by the gripper assembly, subsequently decreasing the amount of light reflected back to the light source by changing the distance between the lens and the surface of the covering in the first direction from the predetermined distance to a second distance, while the workpiece is gripped by the gripper assembly, and detecting when the lens is spaced apart from the surface area of the covering by the predetermined distance by detecting when the amount of light reflected back to the light source stops increasing and starts decreasing while the workpiece is gripped by the gripper assembly.

209. A method as set forth in claim 208 wherein said step of detecting when the amount of light reflected back to the light source stops increasing and starts decreasing includes the steps of storing data corresponding to the amount of light reflected back to the light source at each of a plurality of distances between the lens and the covering, comparing the stored data for a plurality of distances between the lens and covering, and determining when the stored data indicates that the light reflected back to the light source stops increasing and starts decreasing.

210. A method as set forth in claim 209 wherein said step of measuring the thickness of the covering on the workpiece includes the steps of providing a source of light, directing light from the light source against a surface area of the covering with a lens while the workpiece is gripped by the gripper assembly, reflecting light from the surface area to a photosensor, decreasing the amount of light reflected back to the photosensor by effecting relative movement between the lens and the surface area of the covering in one direction while the workpiece is gripped by the gripper assembly, subsequently increasing the amount of light reflected back to the photosensor by continuing to effect relative movement between the lens and the surface area of the covering in the one direction, while the workpiece is gripped by the gripper assembly, and detecting when the lens is spaced apart from the surface area of the covering by a predetermined distance by detecting when the amount of light reflected back to the photosensor stops decreasing and starts increasing as the distance between the lens and the surface area of the covering is changed in the one direction while the workpiece is gripped by the gripper assembly.

211. A method as set forth in claim 210 wherein said step of detecting when the amount of light reflected back to the photosensor stops decreasing and starts increasing includes the steps of storing data corresponding to the amount of light reflected back to the photosensor at each of a plurality of distances between the lens and the surface area of the covering, comparing the stored data for a plurality of distances between the lens and surface area of the covering, and determining when the stored data indicates that the light reflected back to the photosensor stops decreasing and starts increasing.