With the rapid development of modern science and technology, the variety of cutting tools made of superhard materials such as polycrystalline diamond (PCD) and polycrystalline cubic boron nitride (PCBN) is becoming more and more diverse, and their performance is constantly being developed and improved. The abrasive particle size of the blade ranges from tens of microns, a few microns to nanometer level; the content of diamond and cubic boron nitride is divided into low content, medium content and high content; the binder includes both metal, non-metal and mixed materials; the thickness of PCD layer ranges from millimeters to micrometers; the bonding method between PCD layer and hard alloy substrate includes plane and corrugated surface; PCD layer has different characteristics such as high wear resistance, high toughness, and high heat resistance.
At present, the application scope of PCD and PCBN cutting tools has expanded to industries such as automobiles, aerospace, precision machinery, household appliances, wood, electronics, and electrical appliances, and is used to make turning tools, boring tools, milling cutters, drills, reamers, taps, saw blades, engraving tools, and shaving tools.
Although the development of PCD and PCBN cutting tools is so fast, the difficulty in tool edge grinding caused by its high hardness has always been a problem for most users, and the regrinding of blades is mainly completed by the original tool manufacturer. Not only is the tool price high, but the delivery time is long, and it also occupies the circulating fund of enterprises and institutions. Therefore, it is necessary to study the grinding characteristics of PCD and the grinding technology of PCD cutting tools seriously.
Based on the grinding characteristics of PCD, the requirements for grinding equipment of PCD with diamond grinding wheels are much higher than those of general tool grinders. The main requirements are:
Due to the high hardness of PCD material, the grinding machine must have a high ability to resist deformation, especially the spindle system and tool clamping system. The grinding force during PCD cutting tool grinding is generally between 100-500N. Therefore, the machine tool requires a large shaft diameter, and the axial rigidity and strength of the bearing should be high.
The grinding ratio of PCD is extremely low, and the grinding mechanism of PCD is mainly the result of a mixture of mechanical actions such as micro-shattering, wear, shedding, and cleavage caused by continuous impact of diamond grinding wheels on PCD materials, as well as thermal-chemical actions such as oxidation and graphitization. Therefore, the use of short-stroke oscillating mechanism is conducive to improving grinding efficiency and improving the quality of tool edge. The swing distance is generally 0-50mm, and the swing speed is 20-60 times/min.
Due to the hardness, brittleness and wear resistance of PCD materials, its cutting edge is usually designed as an arc shape to help reduce the amplitude of relative vibration between the tool and the workpiece.
In order to achieve the machining of the arc-shaped cutting edge, the tool clamp of the machine tool should have a high-precision rotary function and an online detection device for the radius size and quality of the cutting edge arc. This can avoid positioning errors caused by multiple clamping, and at the same time, can greatly improve processing efficiency.
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