My production team is facing the ID shrinkage on brass metal insert after plastic injection overmoulding. Before the Moulding process I performed measurement on the brass inserts and it found within specification, but after the Moulding found that there is a decrease of 40 to 50 micron in ID after the over mould. Appreciate if anyone could give some useful suggestion we can contribute towards our RCA.

Our internal RCA strikes out the below possibilities after testing.

Tool
Moulding Machine
Raw Material
Process temperature.

The only thing which we yet to try out is the plastic resin material (using PEEK CF30 & CF40)

Thanks in Advance.