Sometimes even the best of engineers may need help when designing plastic parts. So The Protomold Co. Inc., Maple Plain, Minn., (protomold.com) provides the on-line Design Guidelines, which lists many design tips and gives information on topics such as how to choose a resin.

The guide says a few things designers should consider include:

Wall thicknesses according to resin used

An illustration shows several materials and the best wall thickness for each. For instance, polyethylene parts are listed as requiring wall thickness of 0.030 to 0.200 in.

Importance of uniform wall thickness

Consistent wall thickness eliminates warped or distorted parts. The guide explains and shows why avoiding thick areas produces better designs.

Proper use of draft

Along with reinforcing fillets, draft adds rigidity to part ribs and strengthens molds. The guide advises using at least a 0.5° draft angle on all vertical faces.

In addition, Protomold-specific tips specify details such as limitations on part sizes and complexities. Other tips tell how best to design for the aluminum molds, which the com pany cuts on 3-axis CNC milling machines.

View the Design Guidelines at protomold.com/designguidelines.