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10 Top tips when designing for plastic injection moulding

When using injection moulding to create plastic parts, you gain great scalability and design flexibility to produce parts of all complexities. There is great uniformity of plastic parts when produced by injection moulding that sees hundreds or millions of identical parts produced to the same specification. However, it can be expensive to build and maintain the injection mould tools necessary for the process and more challenging when tooling changes are required.

Here at CJ Tool & Mouldings we have our own in-house tool-room, where we manufacture new tooling and can carry out refurbishments and modifications of existing injection moulding tools. Find out more here.

Below, our experienced team have created a list of their top 10 tips when designing for injection moulding:  

  • Uniformity – Throughout your part you should keep a constant wall thickness. This will provide the best flow. We recommend a minimum of 1mm and a maximum of 4mm for conventional injection moulding.
  • Smooth – You should use radii when possible to avoid sharp transitions between wall sections.
  • Add Draft – It’s helpful to add a draft angle to the faces of your part to release it from the tool, however, it can cause design challenged especially for mating parts.
  • Zero Draft - Avoid surfaces with zero draft unless necessary. If you do need a zero-draft area try to minimize it to just a portion of the face, not the whole surface.
  • Simplicity – You should avoid undercuts and if simpler doesn’t work for your part, lifter and slides allow features to be formed that are undercuts in the main pull direction. If so, you should leave 2 to 3 times the width of the feature to allow the lifter or slide to travel.
  • Transition - If plastic flows through features moving from greater to lesser wall thickness, parts will form better.
  • Cosmetics - Eliminate the visibility of blemishes on cosmetic surfaces by avoiding gates, ribs, screw bosses etc. Rib heights should be 3x or less than the wall thickness and rib bases should be 60% or less of the wall thickness.
  • Use Datums - To define territory and establish part interfaces and interactions to the overall system, so the structure matches the designs.


Added: 21 Mar 2018 14:00

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