5 most important design guides for injection molding plastic parts

Injection molding is a highly efficient manufacturing process used to produce plastic parts in both small and large volumes. Unlike rapid prototyping, injection molding requires the creation of a mold or tool, which can be time-consuming and costly due to the use of expensive steel. As such, it is essential to avoid errors during the tool-making process, making the perfect design of plastic parts crucial. To assist you in this endeavor, we have compiled the top 5 most important design guidelines for injection molding plastic parts. By following these guidelines, you can ensure a streamlined and cost-effective production process for your plastic parts. Additionally, these design rules can help you optimize your injection-molded parts for maximum durability, functionality, and aesthetic appeal, ultimately boosting your product’s overall value

the 5 parts design rules:

To create injection-molded plastic parts that are functional, durable, and aesthetically pleasing, it is crucial to follow a few essential design guidelines. Here are five of the most important guidelines to keep in mind when designing parts for injection molding.

  1. Incorporate Draft Angles

To ensure that the part can be removed from the mold core, it’s essential to apply draft angles. For vertical walls that are perpendicular to the direction of mold pull, a draft angle of at least 1 degree is necessary. If you’re using textured walls, the draft angle should be a minimum of 3 degrees. Failure to apply draft angles can result in the part sticking to the core of the custom made tool, making it challenging to release the product.

5 important part design guides : draft angles

  1. Use Uniform Wall Thickness

To promote smooth flow of molten thermoplastic material during injection molding, it’s essential to design uniform wall thicknesses. By doing so, you can create products that cool uniformly, resulting in higher quality and consistency. In the picture , herunder, you can see thick sections that needs to be hollowed out.

uniform wall thickness

  1. Account for Shrinkage and Warpage

To reduce the likelihood of shrinkage and warpage, it’s necessary to hollow out thick sections of the part. This will minimize the stress on the part and ensure it retains its shape during the cooling process.

  1. Round Edges and Corners

To produce a smooth, aesthetically pleasing product, round the edges and corners of your part. The radius for interior edges should be at least 0.5 times the wall thickness, while exterior edges should have a radius equal to the sum of the interior radius and wall thickness. Avoid sharp transitions between wall sections by using radii when possible.

  1. Strategically Position the Parting Line

The parting line is where the two halves of the mold meet, and its placement can impact the mold’s opening direction and the draft required for the part’s features. By placing the parting line along an edge instead of a flat surface, you can hide the seam and reduce the chances of flash. This will improve the part’s appearance and functionality and minimize any required post-processing.

By following these essential guidelines, you can optimize your injection-molded plastic parts for cost-effectiveness, durability, and quality.