Fig. 4 shows a schematic of the newly developed method,
which has had a patent application filed [8]. The main
changes have been the addition of a unit to the existing
EDM head. The unit consists of a set of guiding collets
which allow the electrode to be fed through them. The guiding
collet angle can be changed to enable the required hole
taper to be achieved. The gap between the workpiece and
the guiding collets is fixed. As the Z axis moves towards the workpiece, it is only the electrode that advances. The
complete unit rotates which is a fundamental part of the
design, the rotation helps flushing and improves cycle time
and is also required for the concept to work.