Traditional Molding: In order to understand the differences in molding techniques, it is important to define what we mean by a traditional molding process and to then differentiate it from the new technique and its various refinements. Injection molding evolved from a manual process in the 1940’s, when machines were virtually unsophisticated arbor presses where
plastic was squeezed into a mold, which was manually clamped by using hand force, much the way a drill press is operated today. Material was fed into a cylinder, heated by heater bands, and a plunger was used to squeeze the plastic into the mold. There was only one pressure squeeze. Plastic was
squeezed into a cold mold, the pressure was jelled until the part solidified, pressure was released, the mold was opened, and the part was taken away. Injection molding and the concept of how molding occurred evolved from this basic technique. This is what we now call traditional molding.