Why mold design matters

There was a great article in Design News this month on the importance of mold design as it relates to part design and quality:

The four simple rules are:

  1. Establish nominal wall thickness.
  2. Allow draft to make it possible to easily remove the part from the mold cavity.
  3. Watch rib-to-wall ratio. The section where a rib joins a nominal wall should not be more than two thirds of the nominal wall. Drop that to 50 percent on crystalline resins, such as polypropylene or nylon, because of greater shrinkage rates. Make sure radii do not cause sink or inhibit part ejection.

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