Machining, part processing drilling

Cutting force is the most fundamental, and in many cases the most significant parameter in machining operations. In the main manufacmring processes like mming, milling, and drilling, they can cause part and tool deflections which may result in tolerance violations. 

External cylindrical lapping is used to process external surfaces of cylindrical parts. Therefore, the workpieces are moxmted radially on a workpiece holder on a two-face machine, whereby the parts scroll with an eccentric motion between the lapping disks. This process is used to reach very high shape precision, required, for instance, for jet needles in injection pumps. Cylindrical lapping of drilled holes is realized with cylindrical bushes, which describe rotating and lifting movements. Because of this kinematic, high surface qualities are reached, which are unable to be accomplished by other processes (Paulmann 1991). 

Machining is also used in combination with other processes. Some processes require that gates be removed or parts trimmed by mechanical means before they are ready to be used. Machining may be used to create details the process cannot create. An example of this type of application would be holes in thermoformed parts. Finally, machining may be used because the product s production volume is too low to warrant the additional tooling cost necessary to mold the detail into the part. An example of this type of application would be a hole in an injection-molded part parallel to the parting line that would require an expensive side action. The additional amortization cost could exceed the cost of drilling the hole for low volumes. 

The preferred method of registration of the panel to the machine table is to use the full panel and the tooling holes previously drilled. Tooling holes internal to the part provide for the highest accuracy, although manufacturing panel tooling may be used if considered earlier in the process. 

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