1. Post-filling

1.1 Definition of post-filling

After flow-rate filling, additional material is introduced into the mold to compensate for cooling shrinkage, by imposing a compaction or holding pressure. The switchover from "forced flow" to "forced pressure" mode can be set according to screw position, hydraulic pressure or pressure measured by a sensor located in the cavity. It is often difficult to know whether the changeover takes place before or after the end of filling. In the latter case, the compaction phase begins in "imposed flow" mode (if the machine can ensure a constant flow rate when the mold is full), whereas in the former case, the end of filling is at imposed pressure, and the flow rate is no longer controlled. Two stages can be distinguished after the end of filling: