diamond-pellets

To improve the performance of diamond-impregnated pellets, researchers evaluated many different diamond and bond compositions on a variety of materials and made extensive measurements in five different areas: the surface roughness (Ra), the material removal rate (mrr), the pressure required for operation, the amount of loading or dulling incurred over a period of time, and the lifetime or grinding ratio (G-ratio, defined as the volume of product removed divided by the volume of pellet lost) of the pellets. They found that these five characteristics are frequently interrelated. For example, increasing the operating pressure typically increased the mrr. Pellet compositions engineered to have a larger mrr also showed a higher Ra, while pellets designed to have a larger G-ratio generally exhibited lower mrr, a lower Ra and a shorter loading time. Most changes in composition to enhance one characteristic degraded another. However, researchers discovered that they could improve the overall performance of the pellets by using the newer high-quality diamond powders with high-strength bonds, and by carefully adjusting the composition and concentration of the separate components. 
The test data also showed that the mrr generally declined over time, with the decline becoming progressively worse after just a few minutes of lapping. This decline could be quantified by a decay constant (D), which was unique to each combination of pellet and lapped material. Frequently, the mrr approached zero as the lapping process continued, at which point the pellets had to be redressed to restore the original mrr. When the lapping process was resumed, the decay of the mrr was repeated. Again, researchers discovered that by using the newer high-quality diamond powders with high-strength bonds, and by carefully adjusting the composition and concentration of the separate components, they could slow the speed of decay. 
The high-performance fixed abrasives developed through these tests range from very aggressive lapping to fine cutting. Using the refined pellets, glass and quartz can be lapped up to 80 microns per minute on existing lapping machines—significantly faster than with conventional pellets or loose abrasives. Additionally, while the pellets have been successfully tested in pressures as high as 45 psi, they also work well with the lower pressure constraints often found in glass and ceramic lapping. Unlike conventional pellets, which required pressures of 4-6 psi and higher, the new pellets can operate at 1-3 psi—and even lower, in some cases. For example, glass lapping pellets are available that operate successfully down to 3⁄4 psi.