The work presented in this paper has shown that high
quality reverse tapered holes can be produced, showing excellent
hole form, with hole diameter variation within 3 m
and cycle times similar to standard EDM for straight holes.
The k-factor values up to k = 6.5 have been produced. The
quality of hole surface finish has been maintained at R
=
0.3 m. The results have shown that the process is repeatable
and stable. The solution can be applied to existing equipment
without the need for a major retrofit. The results have
shown that holes with a neck effect have been eliminated.
One main application area is for diesel fuel injection nozzles
to improve emissions from diesel engines without the
need for higher injection pressures or smaller diameter holes.
The developed method has not only enabled tapered holes
to be produced but has also improved the general hole form
and diameter consistency seen with standard EDM, as has
been shown by the results presented in this paper.