injection molding
...he process begins by a heating a polymer until it reached a highly plastic state. While in the plastic state using the reciprocating screw or screw preplasticizer machine it is placed in the clamping unit where it is held together. The reciprocating screw rotates and moves the polymer forward for injection. As the screw rotates it acts to melt, mix and pump the polymer to prepare it for injection. Once the polymer (in a highly plastic state still) is injected into the mold cavity, the mold is cooled. The mold has a gate, which limits back flow and directs the flow of the melt into the mold cavity. Once the mold has cooled and the polymer has solidified the mold can be removed and the part can be ejected out. When the gate freezes the screw begins to rotate again and the part is ejected. This ends the cycle. Cycle times range due to hold time (amount of time the polymer needs to solidify.) Advantages to injection molding are, flexibility in design, low tolerance, and the ability to produce a diverse range of products, minimum labor, scrap, and finishing. Some of the disadvantages are the high startup and running costs, difficulty in accurate cost prediction, and the high c...