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  • Locking mech for injection molding

    Discussion in 'The main mechanical design forum' started by Hazel96, Apr 20, 2013.

    1. Hazel96

      Hazel96 New Member

      Apr 2013
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      I am designing a plastic electronics housing. It will be made using injection molding. I have a living hinge on one end and I need a locking mechanism so they can open and close the housing without it actually locking. I just need something that secures it when shot. This applications is used everywhere on retainer cases, plastic containers etc.. Are their any locking mech designs on the Internet or 3d cad models with a locking mech design out there that would work with injection molding or even 3d printing?
    3. Michael Ross

      Michael Ross Well-Known Member

      Mar 2012
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      I feel like a barely understand the question. Sounds like a spring latch. But, you haven't even said what material is to be used - so how can I offer useful help?

      I have designed a number of spring latches for plastic parts. I never saw any prepared solutions. I asked the mold maker what were important features of the design so that it could be molded well. Some solutions are personal preference. Always radius corners so there is no stress concentration where the feature is anchored. Both the latch and the strike will have overhangs in the mold to be addressed.

      You must understand the need of draft on the features, the parts of the mold need to "kiss off" properly - hard to describe with words only, but the metal parts of the two mold halves are better off touching each other flat to flat, rather than sliding by each other. You might want to Google mold kiss off.

      For the latch itself - if it is a cantilever that deflects one end then the length of the spring, its width and the height that bends determine the stress that is present when it moves. You have to get that right for the material you choose. There will be large differences between, for instance, polyethylene and polycarbonate. Only certain materials are appropriate for living hinges.

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