Thermoplastic injection molding machines produce molded plastic parts by converting plastic pellets into molten material, injecting the molten plastic into a mold, and cooling the plastic material. The mold consists of two halves. One half is connected to a movable platen and the other is connected to a stationary platen. As the machine prepares to inject molten plastic into the mold, the platens close and press the mold halves tightly together. When the plastic is cooled, the movable platen retracts, and the solidified plastic parts are removed.