Micro-Electrodischarge Machining

One of the limitations of PCM is that minimum hole diameter (0 MIN) depends on the thickness (T) of the material being etched and in general, 0 MIN=l.IT for standard applications (Ref. 1). However there is an increasing number of applications now requiring high aspect-ratio holes in sheet and foil materials where a hole diameter (0) may be 0.1T – 0.2T and where 0 may be of the order of 10-100 um. Thus the industrial requirement may be a 40 um diameter hole in a 100 um foil – an aspect ratio of 2.5 which is impossible to achieve by conventional (isotropic) PCM of multicrystalline metals and alloys. For the past six years, research at Cranfield has been directed at making arrays of such holes for ink jet printing applications. The work has been supported by a local company to the extent that Cranfield now has its own Charmilles micro-electrodischarge machining (~EDM) centre comprising two NC machines. One is responsible for fabricating the micro-electrode and the second one is used to fabricate the holes.