Stereolithography Rapid tooling Injection moulding Heat transfer Polyetherether-ether-ketone
The use of stereolithography (SL) as a rapid tooling technique for injection moulding
provides a low cost and quick alternative to hard tooling methods when producing a small
quantity of parts. However, previous work has shown that different characteristics are
developed by crystalline plastic parts produced from SL moulds and those produced from
conventional tooling methods. Differing characteristics means that the parts are not truly the
same as those that would be produced by hard tooling and highlights a disadvantage to SL
Such differences are due to the cooling rate experienced by the part. Parts produced
from SL moulds are cooled more slowly than those from metal tools as a result of the differing
thermal conductivity of the mould material itself.
This work concerned establishing the extent of the difference in the heat transfer
characteristics. The different cooling rates were demonstrated by real-time data acquisition.
The results illustrated the very different thermal history imparted on the moulding that are
likely to be the cause of characteristical differences in the parts.
The work then describes how the thermal conditions experienced in stereolithography
moulds can be used to an advantage. A case study details the use of SL moulds for the
injection moulding of polyether-ether-ketone (PEEK) which has high process parameter
The results of the case study have shown that not only is the stereolithography rapid
tooling method capable of producing a low volume of PEEK parts, but also under conditions
that would not be possible using a metal mould. The thermal characteristics of
stereolithography moulds allowed fully crystalline PEEK parts to be produced with the mould
at room temperature; the equivalent steel mould would require a pre-moulding temperature of
~200 C and much higher injection pressures & speeds.