Sharpening PCD/PCBN tools is a cost-effective way to improve the quality of the tool. The final result of sharpening depends on the choice of the grinding wheel grit. The smaller the grit size of the grinding wheel, the lower the grinding efficiency. We can classify the sharpening process of PCD tools into coarse, finish, and fine grinding according to the accuracy of the tool’s cutting edge (see Table 1). According to the actual situation, a reasonable sharpening process can significantly improve the machining efficiency.
|Sharpening process classification
|Cutting edge precision
|Grinding wheel grit
For roughing, either electric or grinding machining is available. Electric machining is efficient and suitable for processing complex tools, such as drills for printed circuit boards and milling cutters for cutting laminate wood flooring. For grinding, coarse grit grinding wheels can be used for large contact areas and high grinding force (300-400N), which can quickly remove the excess machining margin.
Fine grinding wheels are used for fine machining, with a small contact area, low grinding force (100-200N), and low heat generation during grinding but low material removal rate. We should further improve the cutting-edge quality by grinding and polishing.
Finishing is in the middle of the two.
9 Tips For PCD/PCBN Tool Sharpening Process
1. Spindle Accuracy Should Be Good. Generally, The Runout Of The Grinding Wheel End Should Be ≤0.02mm.
If the runout of the grinding wheel is too large, the grinding wheel will intermittently impact the cutting edge during grinding, which will easily cause chipping of the cutting edge and make it difficult to obtain a high precision cutting edge.
2. Grinding Wheel Should Have Good Dynamic Balance.
During the sharpening process, the unbalance of the grinding wheel will lead to vibration of the machine, which will affect the edge quality and machining accuracy of the tool being machined.
3. Grinding Wheels Should Be Preferred To Ceramic Bond Diamond Grinding Wheels.
Because of the self-sharpening of the ceramic bond, the grinding process is easy to occur micro-cracking, making the grinding process more smooth and conducive to improving the accuracy and efficiency of the processed surface. The next choice is to use a resin-bonded diamond grinding wheel with high heat resistance.
4. Always Pay Attention To The State Of The Grinding Wheel And Open Edge Oil Stone Size To Appropriate.
With the diamond grinding wheel processing PCD tool, the grinding wheel will occur clogging, dulling, high temperature, and rapid wear, which will lead to reduced processing speed and vibration patterns, noise, and burns. Usually, choose the use of grinding wheel grain size 1 to 2 soft silicon carbide oil stone as a sharpening oil stone.
5. Because Diamond Is Easy To Chemical Diffusion With Iron Alloy, Accelerates Grinding Wheel Wear, So Should Avoid Grinding Metal And PCD At The Same Time As Far As Possible.
6. The Direction Of Rotation Of The Grinding Wheel Should Be From The Tool’s Front Face To The Tool’s Back Face.
From the force on the cutting edge of the PCD tool during grinding, it can be seen that when the grinding wheel rotates from the front to the back of the tool, the grinding force (the sum of tangential and normal forces) acts inward on the cutting edge, i.e., the tool is under compressive stress, which makes it less likely to damage. The opposite is tensile stress, and the cutting edge is prone to damage. If the tool structure must be reversed sharpening, the use of resin bonded grinding wheels is better than metal and ceramic bonded grinding wheels.
7. In Order To Improve The Sharpening Efficiency, The Back Angle Of The Tool Can Be Divided Into A Large Clearance Angle And A Small Clearance Angle.
Use coarse grit grinding wheel to grind the large clearance angle first because the contact surface is large grinding force; the sharpening efficiency is high; then use fine grit grinding wheel to sharpen the small clearance angle, the width of the small back angle is controlled at about 0.1-0.3mm, the smaller the contact surface, the better the sharpening quality.
8. Try To Complete The Machining Of The Cutting Edge Of The Tool In One Clamping;
9. Choose A Water-based Grinding Fluid For The PCD Sharpening Coolant.
PCD has high hardness and poor heat resistance, so the cooling effect of water-based grinding fluid is better than oil-based grinding fluid, which can improve machining efficiency and edge quality. In addition, sufficient cooling is required during the grinding process, and the flow should not be interrupted. If the amount of grinding fluid is small or the supply is interrupted, it will cause large oxidation or graphitization of the diamond (grinding wheel, tool) and edge breakage of the tool.
Sharpening PCD/PCBN tools can save us a lot of costs, and we should master these tips above to do it better. If you have more questions, please feel free to contact us!