Alongside infeed (i. e., depth of cut), the feedrate considerably affects the total machining time in reciprocating grinding. Increasing the feedrate results in higher average chip thickness and length, and thus in an increase of grinding forces and thermal stress. A repeated start of the grinding wheel to the workpiece and the punctual impact stresses linked with it cause an increase in grinding wheel wear. The surface roughness of the workpiece grows with increasing feedrate. In metal working, feedrates in the range of 25 to 30 m/min are accepted [Spur and Stoefele 1980].
16.2.2.1 The Influence of Infeed
Infeed and feedrate (workspeed) crucially determine the total machining time in reciprocating grinding. An increase of infeed increases grinding forces and thermal stress. The workpiece surface roughness decreases with a higher number of engaged cutting edges. In low removal rate grinding, maximum infeeds are recommended in the range of 5 to 10 |rm [Spur and Stoefele 1980]. Larger infeeds can be achieved in creep grinding and high-removal-rate grinding.
16.2.2.2 The Influence of the Interrupted Cut
As a result of alternating up — and down-cut grinding, and of frequent approaches to the workpiece, high alternating and impact stresses occur at the grinding wheel in reciprocating grinding. Appropriate grinding wheels and bond materials must be chosen to cope with the additional wear caused by this effect. The abrasive grain must be suitable for alternating and impact stresses and the bond must be capable of holding the abrasive grains firmly in the matrix, even under these conditions. If the bond does not meet this requirement, there will be increased grinding wheel wear and poor surface quality of the workpiece. With higher process forces and temperatures, the risk of displacements between tool and workpiece increases, having negative effects on the work result and on the wheel wear.