The Technique of Lapping
Unit Price Calculation
Lapping machines are graded according to the lapping plate diameter; although this by no means constitutes a full specification, it gives a good indication of the size of the machine. Performance data have to be taken into account. The main factor influencing the price per part is the internal diameter of the conditioning rings, because this encloses the actual area useful for lapping, and allows an estimate of the number of parts acceptable by the machine per cycle. The capacity table (Figure 63) provides reliable data on this. Taking the type FLM 1000 as an example, the conditioning rings are each 400 mm in diameter. The machine can thus accommodate approximately 5800 parts with a diameter of 5 mm, 340 parts with a diameter of 20 mm or 32 parts with a diameter of 60 mm in each conditioning ring. Each load consists of 3 conditioning rings, i.e. approximately 17400 or 1020 or 96 parts. Even assuming the relatively slow cycle time of 20 minutes, for example, a very short machining time per part nevertheless results. If the parts are not rinsed and measured while the machine is already running in the next cycle, the times for these final operations must be added to the lapping cycle time. Production lapping machines often achieve unit prices less than those for grinding.
A further advantage are the low tooling costs. If required at all, only simple plastic workholders for positioning the workpieces have to be produced.