MODEL RELEASED. Plastic moulding. Worker pours plastic powder into a compression moulding machine. The plastic will be heated so that it melts and is then compressed by the equipment at upper right to force it into the desired shape within the mould. The exact technique used for shaping the plastic depends on its chemical properties. These determine the temperature needed to melt the plastic, the time required to mould it, and its ability to flow into its new shape.