NOVEL TECHNIQUES FOR REDUCING COOLING TIME IN POLYMER INJECTION MOULDS USING RAPID TOOLING TECHNOLOGIES

In this research, thermal simulations and injection moulding experiments were
performed to compare moulds having cooling channels of circular cross section and
those with profiled cross section channels. Studies have been performed on the
cooling time reduction in plastic injection moulding by different techniques utilizing
thermal simulations and thermal measurements during experiments.
Rapid Tooling (RT) technique, which is a manufacturing technique used to
produce injection mould tools in a short period of time, has been applied in this
research to fabricate injection moulds having circular and profiled conformal cooling
channels. Injection moulding experiments for parts was done with these RT moulds
using a vertical injection moulding machine.
Manufacturing of mould patterns was done using 3-dimensional Printer Rapid
Prototyping machine which used wax as the build material. Wax patterns were
designed, fabricated and used to fabricate the mould cavity and channels. Aluminum
Filled Epoxy material was used for the fabrication of mould cavities having circular
conformal cooling channels and profiled conformal cooling channels.
As the thermal conductivity of aluminum filled epoxy is much lower than metal
moulds, another innovative concept which was embedding a metal insert around the
cavity, was also applied for enhancing the heat dissipation. The metal insert was
fabricated from aluminum. The concept was tested by fabricating moulds with
aluminum inserts. All moulds were tested by injection moulding experiments with
embedded thermocouples to measure the temperature of the cavity surface and
temperatures were recorded with a data logger. Analysis of the temperature data
indicated that the profiled channels had an increased heat dissipation and reduction of
cooling time of about 17 percent over the circular channels. With the moulds having
aluminum inserts, there was an impressive increase in cooling rate and the cooling
time was further reduced by over 50 percent as compared to moulds without inserts.