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Injection Molding

Injection Molding is the technique of injecting molten plastic into a cold mold and forming a part.

The Basics of Injection Molding

The video shows how the plastic pellets enter the barrel of the molding machine, get transported as they soften and melt and then the melt is injected into the mold, cooled and ejected as a molded product.

A schematic of the main elements of a molding machine are shown below. It consists of a hopper that holds the raw plastic pellets. The hopper feeds the barrel with the plastic. The plastic is melted in the barrel and with the help of the screw (piston) is injected into a mold. The mold being colder than the plastic rapidly cools and solidifies the plastic. The mold is then opened and the part is ejected out of the mold.

The Injection Molding Cycle

The Injection Molding Cycle consists of the Injection Phase, the pack phase, the hold phase and the cooling phase. At the end of the Hold phase the screw begins to recover and pickup the plastic for the next shot. The set cooling time also begins at the end of the hold phase.The Injection Molding Process consists of various Speeds, Pressures, Times and Temperatures. These process variables determine the quality of the molded product and therefore, each of these variable must be optimized in order to have an optimized quality of the part. Optimized part quality leads to less scrap, efficient cycle times and an overall improved part quality.

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