DESIGN FOR MANUFACTURABILITY
Design for manufacturability literally means designing parts, components, mating parts and tooling for the specific production method to be deployed and requires extensive knowledge in various engineering and part fabrication methods. Here is a few of the key points our engineering team considers when designing parts for manufacturability for plastic injection molding:
Parts should be designed to include draft features (angled surfaces) to facilitate removal of the part from the tool. Typical draft angles range from 1 to 2 degrees for parts under 5 inches.
Designing wall thickness with uniform walls and cross sections will simplify the manufacturing process and costs. At the intersections of parts, we normally will consider some radius instead of sharp corners to reduce costs and wear on the tools.
Parts should accommodate areas of thick walls as they cool slower and greater shrinkage will occur. Thin walls cool faster resulting in less shrinkage. We also design boss and gussett features to lessen the opportunity for shrinkage of thick features.
RADII AND CORNERS
We design products with uniform wall thickness at corners. In fact, the minimum radius should not be less than 1⁄4 minimum wall thickness. When significant stress is present, we design in larger radius to distribute potential stress uniformly.
We design these features at 1/2 to 2/3 of the nominal wall thickness and less than 3 times thickness in height. Taper of 1 degree is typical.
WELD PART LINES
The location for these features should be considered and weld lines formed at the mating of the flow fronts of the plastic during molding. The weld line area is more susceptible to cracks and stress failure all of which we take into account when designing your parts and tools.
Surface finish varies from product to product and is based on the client’s specification. We design surface finish at 64 or higher depending on the plastic material. If it needs to be less, we can go down to 7-16 if required.