Essential Manufacturing

14Miscellaneous Metalworking Processes

As well as the processes so far mentioned, there is a multitude of other manufacturing processes widely used in industry today. Some of these are briefly described in this chapter. This chapter is simply intended to provide an introduction to some additional processes of which a good product designer, manufacturing engineer or industrial manager should be aware.

14.1 Electrodischarge Machining

Early in the last century, the introduction of harder, stronger and more heat resistant metals, which were difficult to machine by say conventional turning, drilling or milling, led to the introduction of other processes such as electrodischarge machining (EDM). The process is sometimes termed ‘spark erosion’, since it relies on the eroding effect of electric sparks crossing between two electrodes, one electrode being the tool and one the workpiece being machined. If both tool material and workpiece material are the same then the greater erosion occurs on the positive electrode; therefore, to minimise tool wear and maximise metal removal rate, the workpiece is made positive. The principle of operation is shown in Figure 14.1. The electrodes are immersed in a dielectric fluid, that is, a liquid that can sustain an electric field and act as an insulator, such as paraffin. The sparking occurs due to heavy electrical discharges across the gap between the electrodes. The interval between the sparks is around 0.0001 s, the sparks releasing their energy ...