Updated: Apr 9, 2021
Injection Molding is a manufacturing process where molten plastic is squirted into a mold (typically steel or aluminum) to form a plastic part. It is typically used in mass-production where thousands of parts are required, but can be adapted to dozens or hundreds of parts.
If you're not an injection-molding expert, then designing molded plastic parts can be intimidating. How many undercuts am I allowed to have? Can I have this shutoff next to this feature? Does this draft angle allow this surface finish? Can I pull a slider through this mold half? Where will my ejector pins need to be located? Fortunately, the 80-20 rule applies to Design for Molding. Spend 20% of your time to get the part 80% of the way ready for molding, then get feedback from vendor. I like to send my parts out to my molding vendor before my design is final. This gives the molding company an opportunity to see the parts early. When they can see the parts early, they provide feedback before the design is complete. I recently worked on a complex electronics internal chassis part. The part required several side actions and complex hand-loaded inserts in the mold. The cycle time was long, and the manual labor associated with loading the inserts made the parts expensive. Fortunately, the part was internal, so aesthetics were not a big concern. This meant that tooling shutoffs and slides could leave scratches/scuffs/flash on my part without affecting functionality. My tooling vendor reviewed the files early on and provided DFM report on the parts. The DFM report contained no surprises, and confirmed my tooling complexity assumptions. They came up with a clever method of splitting a complex part to simplify molding. We ended up designing three individual molds were all simple with short cycle time. The short cycle time with low manual labor input meant that the individual components were extremely low cost. The three parts were Ultrasonic Welded (UW) together and the overall cost was low. Do you have challenging injection-molded parts on your device? Have you run into challenges with design for molding? Call me to discuss
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