The Technique of Lapping
Speed of the Working Plates
The rate of material removal is largely proportional to the rotational speed, or to the distance covered per unit of time. The maximum rotational speed is limited due to the centrifugal force occurring. At high speeds, the lapping fluid gets thrown outwards, and relatively high, narrow workpieces undergo a wobbling motion that is detrimental to flatness and parallelism. High speeds are by no means a disadvantage for the actual lapping process. However, it remains to be seen whether a rolling process of the lapping grain can still take place (also see Pages 3 + 4). Most practical experience seems to indicate that this is not possible. Scratching traces on the workpiece surface indicate more of a “honing” process, i.e. the working plates would require ring-shaped or cross grooves to prevent the lapping agent from being thrown off. Working plates with bound grit permit higher speeds, if this is possible with the material in question.
Newer designs of lapping machines incorporate a soft-start facility or stepless speed control of the working plates, step-controlled pressure loading, cooled working plates, digital time measurement and automatic loading, turning, unloading systems etc. as the minimum equipment complement (Figure 43).