A Guide to Injection Molding

Thermoplastics, such as nylon, polypropylene and polystyrene, become flexible when heated. This property forms the basis of the manufacturing process known as injection molding. Injection molding is just one of several methods than can be employed to form plastic products, but is, in fact, the most widely used method worldwide.

Raw Material

The raw material for injection molding is granules of plastic powder -- often known as resin -- in the form of round pellets or tubular pieces. The granules are stored in a hopper and fed into the barrel of the injection molding machine under gravity.

Injection

The barrel of the injection molding machine is heated to high temperature and the granules are pushed through the barrel by a screw thread, so that they become liquid. The screw thread forces, or injects, the molten plastic into a mold.

Molding

The mold is held closed under high pressure and cooled so that the molded product solidifies and cools rapidly. Once the plastic has cooled, the mold is opened, usually automatically, and the finished product is removed.

References

• Technologystudent.com: Injection Molding of Plastics
• Plastics.com: Basics of Injection Molding