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Injection Mold Design

Injection molding is the fastest mass manufacturing process available for plastic parts. As such, you can get your parts to consumers faster and cheaper than any other method. However, designing your parts to be injection molded can be quite tricky if you don’t know the best practices for this specific process. In this article, we’ll cover the injection molding process, design concerns, and common injection molding design problems.

The Injection Molding Process

Injection molding is a mass manufacturing process that uses a mold to rapidly produce many identical parts. While both plastic and metal can be injection molded, this article will focus on plastic injection molding.

To produce a part via injection molding, plastic pellets of your chosen material are fed through a hopper down into the barrel of the machine. A ram and screw mechanism then pushes the pellets toward the heated end of the barrel where they begin to melt. Once the pellets are melted, the liquid plastic is pushed through the nozzle of the barrel and into the mold cavity. Through the use of water cooling channels around the mold, the plastic can quickly cool and solidify so that it holds the shape of the mold. The mold is opened, and ejector pins push the part out of the mold cavity. The mold closes again so that it is ready for the next injection. This is considered one mold cycle. Depending on the material and the size and design of the part, a mold cycle can take as little as two to five seconds.

The injection molding process is pretty straightforward, but it can only perform as well as the part is designed. Knowledge of best practices for injection molding and careful design of your part are crucial to producing the level of quality you desire. Poor part design can lead to big problems, such as sink, warp, or voids. Additionally, if your part design cannot be easily ejected from the mold, it can cause damage to the part or mold itself. If this happens or you have to do a redesign that will require a new mold to be milled, this can cost thousands of dollars and hundreds of hours to correct. Below, we discuss the main concerns with injection mold