Study on a new micro injection moulding process by converging micro injection with hot embossing pVT-characteristics

In the recent years, the micro injection moulding process was well established. A lot of machines from different suppliers are now on the market with production capabilities for three-dimensional micro parts with weights below 1 g. One key feature of this process, in comparison to conventional moulding, are typical filling times below 100 ms and high cooling rates. In contrast, a precise injection moulding process is characterized by a packing procedure, following an ideal pvT-course during cooling via a small gate. For micro cavities the packing process window is typically below 0.1% of the whole cycle and can be too small to produce defect-free and low tolerance polymer parts. Combining velocity controlled filling cycle of micro injection moulding with a force/pressure controlled isobaric packing cycle in the parting plane, and a pressure follows temperature cooling, like in hot embossing, can be a good solution to overcome this today process limits. Trials on a LED mobile phone flash optic with a new generation of machine using an innovative feedback control system and a special designed tool showing very promising first results. Compared to a conventional injection compression process, even in the lower mould temperature range (none-stationary, frozen layer formation), the new process have higher productivity and a better part quality compared to the state of the art.