Injection molding is a versatile process for creating high-quality components and parts from plastic resins. In injection molding, the plastic material is heated to liquid form and injected under pressure into a mold. Once there, it is carried through channels — called runners — to mold cavities machined in the shape of the finished part or product. After cooling and solidifying, the two halves of the mold are separated and the finished parts are ejected from the cavities. The next step of the process is typically a quality check. Mold design and product design are critical aspects of injection molding. As such, good injection molding design is necessary to ensure that the process runs smoothly.

The following injection molding design guide provides injection molding design tips and factors to consider.

Your Injection Molding Design Guide

Design guidelines for injection molding ensure that parts are created according to the necessary design requirements and the process runs as efficiently as possible. When considering how to design for injection molding, take the following into account:

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Keep the thickness of parts as uniform as possible — In injection molding, it is important that the molten plastic material can flow into the mold cavity as smoothly as possible. This ensures uniform cooling and hardening. Injection molding is best suited for pieces with generally uniform wall thickness, to facilitate this consistent flow.

Design rounded corners — For similar reasons, rounded corners are preferable to 90-degree angles in molded part design. Sharp corners are more difficult for most molding resins to fill completely, and can result in a higher rate of part rejections.

Consider part size — Injection molding machines are available in a wide range of capacities and sizes. However, part size will impact the number of pieces that can be produced in each cycle. This can affect the timeline for your project.

Understand different types of materials — There are thousands of resins available for injection molding, each with different physical properties. Consider the needs of your product and choose your material accordingly. For example, if you can incorporate design factors like gussets and ribs to provide structural strength, you may be able to choose a lower-cost material.

Assess the type of finish your product will need — Because injection molded parts take the form of the mold cavity, textures can be designed into the mold to provide a desired surface finish without the need for secondary processes. Take this into account when designing your mold, so that you can identify efficiencies in the overall production process.

Why the Design Process Is Important in Injection Molding

Now that you have an understanding of how to design plastic parts, we will provide information on why this process is desirable:

Injection molding is a versatile, yet unique process — Although injection molding is suitable for an incredibly wide range of parts and product types, it’s important to follow the design best practices that have been identified for it. Following these processes will ensure your part is produced according to spec. If the product cannot be designed to adhere to these processes, you may need to consider a different manufacturing method.

Good design ensures part quality — Poorly designed molded parts are subject to production defects that can affect the integrity of the finished product, including unwanted cavities or gaps in the product, weakened structural elements and incomplete parts.

Increased quality means increased efficiency — Part defects should be identified during the quality control step of production. The more pieces are rejected, the longer your production time and the higher your costs.

Molded Product Design With Crescent Industries

As an expert in custom injection molding, Crescent Industries takes all the above guidelines into account to design a project that will provide high-quality parts at a reasonable cost. We work with you to develop designs and prototypes that ensure your product will fulfill its requirements while being manufactured efficiently. For more information, contact us.

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Topics: custom plastic part design