PCD、PCBN tool sharpening process selection and characteristics

Choice of sharpening process

One of the purposes of cutting tool sharpening is to obtain cost-effective cutting edge quality, and the key to the quality is the choice of grinding wheel particle size. The finer the particle size of the grinding wheel, the smaller the cutting edge chipping, and the lower the grinding efficiency. For this reason, the PCD cutting tool sharpening process can be divided into three processing stages: coarse, fine, and fine according to the accuracy, use (see Table 1) or the degree of failure (see Table 2) of the cutting edge of the tool. Formulating a reasonable sharpening process according to specific conditions can greatly improve processing efficiency.

Rough machining does not require high cutting edges, so you can choose electrical machining or grinding. The electrical processing efficiency is high, and it is suitable for processing complex tools, such as drill bits for printed circuit boards, and forming milling cutters for cutting laminate flooring. Coarse-grained grinding wheels can be selected during grinding, with large contact area and high grinding force (300-400N) during sharpening, which can quickly remove excess machining allowance;

Fine-grained grinding wheels are used for fine processing. The contact area during sharpening is small, the grinding force is low (100-200N), and the grinding heat is low, but the material removal rate is low. This stage is mainly through grinding and polishing to further improve the quality of the cutting edge. Finishing is among the two.

Key points of sharpening process

1.The accuracy of the spindle should be good, and the end face of the grinding wheel should be ≤0.02mm

The end face of the grinding wheel beats too much, the grinding wheel intermittently impacts the cutting edge during grinding, it is easy to cause the cutting edge to chip, 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 quality and machining accuracy of the cutting tool being processed;

3.For sharpening grinding wheels, ceramic bond diamond grinding wheels should be preferred

Because the ceramic bond is prone to microcracks during the grinding process, the abrasive grains are renewed and self-sharpened, so that the grinding process is stable, which is beneficial to improve the accuracy and efficiency of the processed surface; secondly, a resin bond with higher heat resistance can be selected. Diamond grinding wheel;

4.Pay attention to the sharpening of the grinding wheel at the right time, and the size of the sharpening stone should be appropriate

When processing PCD tools with diamond grinding wheels, the grinding wheels will be blocked, passivated, high temperature and rapid wear, resulting in a reduction in processing speed and vibration marks, noise, and burns. Usually choose the soft silicon carbide stone with a particle size of 1 to 2 smaller than the grinding wheel used as the sharpening stone;

5.Due to the chemical diffusion between diamond and iron alloy, grinding metal and PCD at the same time should be avoided as far as possible.

6.The grinding wheel must rotate from the front of the tool to the back of the tool

It can be seen from the force on the cutting edge of PCD tool during grinding that when the grinding wheel rotates from the front tool to the back tool surface, its grinding force (the sum of tangential and normal forces) ACTS on the inside of the cutting edge, that is, the compression stress of the tool, which is not easy to break the tool. On the contrary, it is tensile stress, cutting edge is easy to collapse. If it is necessary to reverse the grinding because of the tool structure, the resin bonded grinding wheel is better than the metal and ceramic bonded grinding wheel.

7.In order to ensure the quality of cutting edge and improve the grinding efficiency, the back Angle of the tool can be divided into large back Angle and small back Angle.

The rear Angle is first increased with the coarse-grained grinding wheel, and the grinding efficiency is high due to the large grinding force on the contact surface. Then, grind the back Angle with a fine grain grinding wheel, and control the width of the edge band of the small back Angle to about 0.1 ~ 0.3mm. The grinding quality of the small blade on the contact surface is good.

8.As far as possible in one clamping to complete the cutting edge of the tool machining;

9.PCD blade grinding coolant should be water-based grinding fluid.

Due to the high hardness and poor heat resistance of PCD materials, the cooling effect of water-based grinding fluid is better than that of oil-based grinding fluid, which can improve processing efficiency and edge quality. In addition, the cooling should be sufficient during the grinding process, and the flow should not be interrupted, so as to avoid the large consumption (oxidation, graphitization) of the diamond (grinding wheel, tool) and the cutting edge damage of the tool due to the small amount of grinding fluid or the intermittent supply.