Grinding characteristics of PCD and PCD tool sharpening technology

<br> <br> 1 Introduction With the rapid development of modern science and technology, tool varieties made of polycrystalline diamond (PCD), polycrystalline cubic boron nitride (PCBN) and other superhard materials has become increasingly diverse, the performance It has also been continuously developed and improved. The abrasive grains of the blade are from tens of micrometers to several micrometers to nanometers; the content of diamond and cubic boron nitride is divided into low content, medium content and high content; the bonding agent is composed of metal, non-metal or mixed material; the thickness of PCD layer is from From millimeter to micrometer; the combination of PCD layer and cemented carbide substrate has flat and corrugated surface; PCD layer has different characteristics such as high wear resistance, high toughness and high heat resistance. At present, the application range of PCD and PCBN tools has been extended to the automotive, aerospace, precision machinery, home appliances, wood, electronic and electrical industries for the production of turning tools, boring tools, milling cutters and drill bits, reamers, boring tools, saw blades, Sickles, razors, etc.

Despite the rapid development of PCD and PCBN tools, the difficulty of tool sharpening caused by its high hardness has been plaguing most users. The re-grinding of the blades is mainly done by the original tool manufacturers. Not only the high price of the tool, the long delivery time, but also the liquidity of the company. Therefore, it is necessary to seriously study the grinding characteristics of PCD and the sharpening technology of PCD tools.

2 PCD tool manufacturing process

The production process of PCD cutting tools generally includes polishing, cutting, fixing, sharpening, quality inspection and so on. PCD superhard material blanks are usually 1/2, 1, 2, 3, 4 inches in diameter, and their surface is generally rough (Ra2 ~ 10μm). It can not be directly used to make tools. It needs to be polished to make the surface mirror surface (Ra ≤0.01μm), then processed into blades of certain geometry and size by laser cutting or wire EDM, and further mechanical and chemical treatment of the blade and the substrate to be fixed, then silver-based brazing It is fixed to the substrate and finally sharpened by a diamond grinding wheel.

One of the keys to PCD cutting tool manufacturing technology is the sharpening quality of the cutting edge. The lack of ideal sharpening technology and technology for high-quality cutter head materials will result in waste of resources. The use of a good sharpening process will improve the quality of the tool and reduce the cost of tool use.

3 Grinding characteristics of PCD materials

PCD is made by special treatment of diamond and a small amount of binder sintered under high temperature and high pressure. The disorderly arrangement of diamond grains gives the PCD a uniform, extremely high hardness and wear resistance. PCD can be used for cutting tools, grinding wheel dressing, geological drilling, gage measuring heads, wire drawing tools, sand blasting tools and so on. However, the high hardness and high wear resistance of PCD also bring great difficulties to its processing.

Domestic and foreign scholars have carried out a large number of research and experiments on the processing problems caused by the high hardness and high wear resistance of PCD materials, including EDM, ultrasonic machining, electrochemical machining, laser processing, etc., and have achieved certain effects. . However, comprehensive analysis found that these processing techniques are currently more suitable for roughing of PCD materials. To get a good PCD cutting edge quality, the ideal machining method is still grinding or grinding with a diamond wheel.

Grinding of PCD is mainly the result of a combination of mechanical and thermochemical effects. The mechanical action is the micro-crushing, abrasion, shedding or cleavage of the diamond formed by the continuous impact of the diamond grinding wheel on the PCD material; the thermochemical action is the high temperature formed by the grinding of the PCD by the diamond grinding wheel to oxidize or graphitize the diamond. The result of the mixing of the two causes the PCD material to be removed. Its grinding processing features are mainly:

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