Method for a Shaping of Polycrystalline Synthetic Diamond

The present invention refers to a method for the shaping of polycrystalline synthetic diamond. In prior art methods it is almost impossible and economically quite prohibitive to produce parts, in particular tools, of natural or synthetic diamond with optionally formed edges and faces. It is therefore an object of the present invention to provide a method for economically producing parts of diamond, in particular tools, with optionally shaped faces and edges.

This object is attained in that the processing is performed by spark erosion, whereby a current at low voltage flows on the whole surface to be worked on, between the diamond and an electrode, with essentially equal average current density. Because synthetic, polycrystalline diamonds are generally sintered bodies with a metallic and thus electrically conducting binding materials a processing by spark erosion is possible, whereby practically only the binding material is reduced. The surface quality and consequently the form and precision of cutting edges of tools which can be obtained, is thus determined by the size of the grains of the diamond parts. The size of the grains can be for example 0.04-0.1 .mu.m, leading to a very high surface quality for precision. Thereby a relatively fast erosion of the material can be attained, with a penetration speed of the electrode of about 0.25 mm/min.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a front elevational view of a trueing tool and workpiece for use in connection with the method according to the present invention;

FIG. 2 is a top plan view of the tool and workpiece of FIG. 1, also showing in phantom lines a preferred spark electrode for use therewith;

FIG. 3 is a front elevational view of a profiled cutting tool for use with the method according to the present invention;

FIG. 4 is a top plan view of the profiled cutting tool of FIG. 3;

FIG. 5 is a cross-sectional view of an edge tool and workpiece produced by the method according to the present invention; and

FIG. 6 is a top plan view of the workpiece and tool of FIG. 5.

The trueing tool shown in FIG. 1 presents a layer 2 of polycrystalline, synthetic diamond on a suitable, for example metallic, support 1. The production of a blank with the support 1 and the layer 2 is known per se. As diamond, a material known under the tradename "Compax" or "Syndite" can be used. The front side is then profiled throughout, that is on both layers 1 and 2 by eroding grooves 4 with an electrode 3, which is indicated by a dot-and-dash pattern in FIG. 2, thus creating teeth 5. The electrode 3 has exactly the counterprofile of the profile to be produced.

FIGS. 3 and 4 show a further tool with a profiled true rake. In this case one electrode or if necessary a plurality of electrodes, used together or one after the other, have to be used, which electrodes not only allow erosion of the desired profile but also the required clearance angles with respect to rakes 6. The other respective parts are designated as in FIG. 1 and 2.

FIGS. 5 and 6 show a further trueing tool with a profiled true rake. In this case a spark electrode is used which is lowered from above towards the top surface of the diamond layer 2, for forming the profile of the rake, relative the flat step 7. In a second phase, the rake 8 is formed by erosion if not present in the blank.

As already mentioned the forming can partially be performed at the blank during the production of the synthetic, polycrystalline diamond layer 2 on support 1. It is thus possible to form the teeth 5 according to FIGS. 1 and 2, the profile form according to FIG. 4 and the rakes 8 according to FIG. 5 already during the production of the blank. It is thus only necessary to finish the piece for the definitive dimensions of the desired definitive shape by spark erosion.

The described embodiments apply to all tools or parts of tools. The invention however is not limited to these applications. In a like manner any highly stressed parts of all kinds, like bearings, working parts and the like can be produced.