What is thermoplastic injection molding?
Thermoplastic injection molding is the most common way to manufacture plastic parts. Thermoplastics are polymers that can be heated to soften or melt, and cooled to solidify as a physical change, rather than a chemical change that takes place during molding of thermoset materials. The thermoplastic injection molding process begins by adding pelletized material to a hopper. In most cases, the material must is dried prior to molding, and frequently requires the addition of a color concentrate before loading. The material is gravity fed into a heated barrel and screw. Rotation of the screw results in shearing action on the raw pellets causing them to melt. The screw rotation also pushes the molten plastic forward in the barrel toward the mold. The material is then injected into the closed mold at high pressure through a runner system to fill all the cavities. The mold is clamped shut under enough force to keep the mold halves together while the molten plastic is flowing. On a cold runner
