Tooling for plastic injection molding

Every tool we make is cut using CNC technology. Each cutting path is automated allowing a high level of accuracy in less time. However, even with this method of production, it can still take weeks to create a complex mold. While we offer our services at designing your tool based on the information you give us, you are also welcome to give us models for your product.

A design was created and modified for an example below. These are some of the simplier changes that can be done to a design to make the part more suitable for injection molding while improving the final product.

Wall thickness

Uniform wall thicknesses on your product will help mitigate the amount of sink and warping that will be created in the piece. For transitions between different wall thicknesses, it will reduce sink to have a gradual transition where the thinner section of the wall is toward the end of the plastic’s flow. A box design below has all wall thicknesses at 0.1 inches thick. Keeping the wall thicknesses between 3/32" to 1/8" is recommended.

Corner radius

Adding radii to internal corners when possible is a great way to reduce the amount of stress put on that area of the product. The box design below additionally has rounded corners on the outside for asthetic purposes.

Mold design tip: Adding a radius to internal corners helps reduce stress

Ribbed wall

Ribs are added to outer walls to improve the strength, but just keep them about half as thick as the outside walls to avoid causing sink on the outside. Sink will occur when a section of a plastic part is too thick, thus is not able to cool easily.

Mold design tip: Adding ribs on external walls helps improve strength

Vertical surfaces

Vertical walls should have a draft of around 3 degrees. This small draft will work provided you don’t have a heavy texture added to your product, in which case it will require more. Adding draft to shutoffs will allow for a better mold shutoff by reducing the metal to metal contact and increasing the lifetime of your tool.

Mold design tip: Adding drafts on vertical walls for easy mold release

If you would like to learn more about the process please visit our Plastic Injection Molding page. Want to see the results? Visit our Gallery page to see parts that have been made using this process!