Hot runner systems are melt delivery systems that maintain a constant supply of melted plastic in between the injection molding machine nozzle and the part cavities of the mold. Hot runners eliminate the scrap associated with cold runner systems because cold runners cool and solidify, and are ejected from the mold with the part. The cold runners then have to be ground up, re-melted, and reused, or disposed of as scrap. With hot runners, generally only the parts themselves are ejected from the mold.
This feature uses pressure controllers at each gate in a mold, and can simulate up to 32 injection locations. Signals come from the pressure sensors of the hot runner system(s) to control multiple hot runner valve gates dynamically, in order to achieve a pre-determined pressure profile for each gate.
The general machine controller, or the central controller, is set to use a high (usually maximum) pressure, to ensure the flow-rate requirement for injecting the melt through the multiple valve gates controlled by the individual pressure controllers. There is no velocity/pressure switch-over, as there is no velocity control stage.
The application is typically used for multi-cavity and family molds, and for multi-gated large part injection moldings, in particular.
The current manufacturing set-up procedure is to use trial-and-error for an individual cavity to get a desired pressure profile as a "finger-print", and then apply it to individual valve gate controllers for the multi-cavity case. For a multi-gated large part, it is difficult to set up, which makes the software simulation very important beforehand.