Design for Plastic Injection Molding

Draft Analysis of a part designed for plastic injection molding.

Designing parts that are intended to be manufactured by plastic injection molding requires special considerations during the design process. The thickness of the plastic throughout the part is of utmost importance. Every type of plastic has its own set of minimum and maximum wall thickness values. Because these parts are formed inside of a mold, the mold must be able to separate in order to retrieve the part without damaging the part or the mold. Parts must be designed with this in mind.

Choosing the proper plastic for the part is the crucial first step to the design phase. Each plastic has its own set of physical characteristics such as chemical reactivity, strength, hardness, ductility, and durability. These characteristics must be considered based on the part’s intended use. Some design elements may be limited due to the physical properties of the material and adjustments to the design would need to be made.

For clean part ejection from the mold, a parting plane must be selected where the mold pieces will separate and the proper amount of draft angle from the parting plane must be applied to every face of the part that is within that section of the mold. More complex elements, like clips and channels, can be designed into the part by making use of shut-offs, cams, and/or side-pulls in the mold itself.

For projects, large or small, we will discuss all of the important design aspects with you and suggest modifications, if necessary, to insure that you receive your desired result.

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