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The Prototyping Blog

the prototyping blog

Wall Thickness Guidelines For Injection Molded Parts

Posted by Molly Skiba on Aug 16, 2019

Resin 4

Aside from resin selection, wall thickness is one of the most important details to pay attention to when designing plastic injection molded parts. Determining the appropriate wall thickness is essential for optimizing the performance, appearance, moldability and cost of your part.  The prototyping stage gives you the opportunity to test your design out with different materials and also gives you the opportunity to tweak your part's dimensions before moving on to mass production.

We're here to get you through that stage as efficiently as possible. If you're new to designing parts for plastic injection molding, these guidelines will help you determine the appropriate wall thickness for your part. If you need more tips, don't forget to download our plastic prototyping toolbox and our injection mold classification guide!

How do you determine the correct thickness?

Wall thickness is ultimately dependent on the material you choose. The chart below outlines some general material thickness guidelines. 

MATERIAL UNIT (INCHES)
ABS 0.045 - 0.140
Acetal 0.030 - 0.120
Acrylic 0.025 - 0.500
Liquid Crystal Polymer 0.030 - 0.120
Long-Fiber Reinforced Plastic 0.075 - 1.000
Nylon 0.030 - 0.115
Polycarbonate 0.040 - 0.150
Polyester 0.025 - 0.125
Polyethylene 0.030 - 0.200
Polyphenylene Sulphide 0.020 - 0.180
Polypropylene 0.025 - 0.150
Polystyrene 0.035 - 0.150
Polyurethane 0.080 - 0.750
Rigid PVC 0.090 - 0.250
Soft PVC 0.025 - 0.150

 

Balancing Weight And Strength

To achieve stronger parts, you should design your part with thicker walls, right? Not so fast. While thickness does add strength, it also adds cycle time and weight which results in a higher part price and a higher chance of warping.  

Thinner walls will reduce the amount of material used and cycle time, resulting in lighter, cheaper parts. However, walls that are too thin can also cause problems. Your parts may come out brittle and break while being ejected from the mold. Minimizing material use should be on the mind of a designer but not so much that it sacrifices the structural integrity of your part.

Some parts are thicker in some areas and thinner in others. In this case, uniform thickness is key for avoiding molding issues. Any variations in thickness should be gradual rather than sudden. This is because thin walls cool faster than thick walls so parts with too much variation will warp or crack. 

Need Help Selecting A Material?

When you have thousands of materials to choose from, it can be overwhelming to choose the right one. Our lead engineer Matt is degreed in Plastics Engineering and can help you select the best material for your part requirements. Contact him any time using this form