The G-ratio corresponds to the ratio of material removed in mm3 from the workpieces and the necessary volume of abrasive in mm3 required for this purpose. In order to make a CBN grinding process economical, a minimum G-ratio of 100 must be aimed for. In the case of optimised processes, G-ratios of 1000 and higher are not unusual. To achieve these high G-ratios, however, the use of neat grinding oil and high peripheral speeds becomes mandatory. With an increase of the peripheral speed, the G-ratio begins to grow exponentionally; the chips become shorter and thinner, the load on the CBN abrasive and the bonding system diminish, and, therefore, the wheel life and the G-ratio increase.
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G-ratio = y mm3 / X mm3 = „Number“
|
Wheel spindle RPM and peripheral speeds
|
Ř grinding wheel(in mm) |
Peripheral speed(m/s) |
Peripheral speed(sfpm) |
Spindle revs.(RPM) |
|
350 |
50 |
10,000 |
2730 |
|
350 |
80 |
16,000 |
4370 |
|
350 |
120 |
24,000 |
6830 |
|
400 |
50 |
10,000 |
2390 |
|
400 |
80 |
16,000 |
3820 |
|
400 |
120 |
24,000 |
5970 | | |
