Manufacturers wish to increase grinding rates for several reasons:
• To increase output from each grinding machine
• To increase output by each machine operator
• To reduce cost per part
An experimental investigation of high removal-rate centerless grinding applied to steel and cast iron allowed process limit charts to be defined [Rowe, Bell, and Brough 1986]. These materials are easy-to-grind materials. Limit charts show operating boundaries for infeed rate, workspeed, and wheel speed. Examples are presented below. With large grinding wheels as used in centerless grinding, the rate of wheel wear was low. It was not possible to achieve an excessive wheel wear condition although this might have been possible if more power had been available. The machine employed had a 75-kW motor. The shape of the diagram means there is an optimum point of operation for high removal rate within the region enclosed by the boundaries. This forms the basis of a control strategy.
Characterization of the process is developed by attention to the concept of a “speed effect” and a “size effect.” Results for the speed effect are distinguished and presented separately from results for the size effect to illustrate the differences due to physical effects.
A two-dimensional surface is presented showing the variation of grinding energy with variations in infeed rate, workspeed, and grinding wheel speed. Because speed and size effects are separated on the surface, it is possible to read directly the optimum grinding wheel speed for minimum energy.
19.9.2 Routes to High Removal Rate
Some of the key features for achievement of high removal rate are as follows.