Grinding characteristics of PCD and PCD tool sharpening technology (4)

5.2 Sharpening process points (1) The precision of the spindle is good. Generally, the end face of the grinding wheel should be ≤ 0.02mm. The end face of the grinding wheel is too large, and the grinding wheel intermittently impacts the cutting edge during grinding, which makes it easy for the cutting edge to collapse, and it is difficult to obtain a high-precision cutting edge.

(2) The grinding wheel should have a good dynamic balance. The imbalance of the grinding wheel will cause the vibration of the machine tool, which will affect the cutting edge quality and machining accuracy of the tool being machined.

(3) The ceramic grinding wheel should be preferred for sharpening grinding wheels. Because the ceramic bond is prone to micro-cracking during the grinding process, the abrasive grains are renewed and sharpened, which makes the grinding process smooth, which is beneficial to improve the precision and efficiency of the machined surface. Secondly, the resin binder with higher heat resistance is selected. Diamond grinding wheel.

(4) Pay attention to the grinding wheel at the appropriate time, and the grain size of the edged stone should be suitable. When machining PCD tools with diamond grinding wheels, the grinding wheel will become clogged, passivated, high temperature and rapid wear, resulting in reduced processing speed and vibration, noise and burns. Soft silicon carbide whetstones having a finer grain size of 1 to 2 than the used grinding wheel are usually selected as the edged whetstone.

(5) Since diamond is easily chemically diffused with iron-based alloys to accelerate wear of the grinding wheel, it is therefore necessary to avoid grinding metal and PCD at the same time.

(6) The direction of rotation of the grinding wheel must be swung from the tool nose to the flank face. From the force of the cutting edge of the PCD tool during grinding, when the grinding wheel rotates from the tool nose to the flank face, the grinding force (the sum of the tangential and normal forces) acts on the cutting edge inward, that is, the tool is affected. Compressive stress, not easy to collapse; vice versa, tensile stress, cutting edge is easy to collapse. If it is necessary to reverse the sharpening due to the structure of the tool, the resin bond grinding wheel is preferred over the metal and ceramic bond grinding wheel.

(7) In order to ensure the cutting edge quality and improve the sharpening efficiency, the back angle of the tool can be divided into a large relief angle and a small relief angle. Grinding the large back angle with a coarse-grained grinding wheel, because the contact surface has large grinding force and high sharpening efficiency; then the small back angle is sharpened with a fine-grained grinding wheel, and the width of the small back angle is controlled to be about 0.1-0.3 mm. The contact surface has a good quality.

(8) The machining of the cutting edge of the tool is completed in one setup as much as possible.

(9) The PCD sharpening coolant should preferably be a water-based grinding fluid. Due to the high hardness and poor heat resistance of the PCD material, the water-based grinding fluid has better cooling effect than the oil-based grinding fluid, which can improve the processing efficiency and the quality of the cutting edge. In addition, during the grinding process, the cooling should be sufficient, and the flow should not be stopped, so as to avoid the large consumption (oxidation, graphitization) of the diamond (grinding wheel, cutter) and the cutting edge of the cutter due to the small amount of grinding fluid or intermittent supply.

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