Injection molding of crosslinking polymers

An expanding crosslinking polymer injection molding system comprising:

• an injection molding machine comprising an injection unit and a mold forming a mold cavity, the injection unit adapted to receive and inject a molten expanding crosslinking plastic material into the mold cavity to form a molded part;
• a controller adapted to control operation of the injection molding machine;
• and
• one or more sensors coupled to the injection molding machine and the controller;
• wherein at least one of the one or more sensors is adapted to measure at least one non-time dependent variable during the injection mold cycle, wherein the controller is adapted to commence a hold profile for the expanding crosslinking polymer part and is further adapted to cause the molded part to be ejected from the mold cavity upon completing the hold profile;
• wherein the hold profile is commenced when the measured at least one non-time dependent variable reaches a first threshold value, the hold profile including restricting additional molten expanding crosslinking polymer from being injected into the mold cavity, wherein the hold profile is terminated when the measured at least one non-time dependent variable reaches a second threshold value;
• wherein the at least one non-time dependent variable includes at least one of:
• a cavity pressure value, wherein the second threshold value includes a substantially constant cavity pressure value over a period of time, or
• a temperature value, wherein the second threshold value includes a substantially constant cavity temperature value over a period of time.