Purpose:
The purpose of the process stability test is to identify any gross mechanical design/construction flaws which will cause part variation over time. In addition, the process stability must be established with no short shots, flash, etc., prior to running designed experiments. The test is run at mid-range resin molding conditions for a period of time to allow thermal expansion equilibrium. In most instances, the mold builder may already have a process where the mold could run comfortably for several hours.
During the process stability test the mold must run with one ejection stroke unless it was designed to cycle with multiple strokes. A robust ejection system will be able to eject the part and runner with one ejection stroke. Multiple ejection strokes per molding cycle increases the wear on the ejection system and increases the molding cycle.
All the steps during the procedure that involve intimate contact with the injection molding machine are to be done by a qualified injection molding machine operator.