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Thread: Design for PIM, maximum thickness strictness?

  1. #1
    Join Date
    Sep 2020
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    2

    Design for PIM, maximum thickness strictness?

    Long time designer, but mostly either metals or 3D printing. I've been studying PIM some, including design guides from various resources, and have some projects coming up converting from 3d printed to PIM.

    I see published wall thickness ranges for various materials, which basically says if not fiber reinforced then pretty much all materials should be less than 1/8" or even much less. I infer that this is partly for warping and likely other bad effects.

    But what if the part is shaped more like say a fat toothbrush handle, could you then get away with making it out of say ABS? What might be the detrimental effects of doing this? Is it common to go over the recommended max thickness some if the part is symmetrical and/or not wide in any direction?

  2. #2
    Join Date
    Oct 2018
    Posts
    22

    Re: Design for PIM, maximum thickness strictness?

    This is a very good question, Starting with the last question first, Yes it common where the design recommendations are ignored and sometimes it is successful. Many times it not because of warping and other defects as you state. But, TIME is among the biggest factor driving the goal to keep part design within the guidelines of material suppliers and plastic engineers with in the industry. Time or the cost of time per part is the where success or failure begins, lives or die. A thick part requires additional time in the molding process to cool. Although there are many creative ideas and post molding operations to reduce the time to mold a part and/or control defects with non-uniform wall thicknesses. It really boils down to time and labor cost to compensate. Even well designed parts can be a challenge to injection mold, sticking within the guidelines improve the odds of success.

  3. #3
    Join Date
    Apr 2020
    Location
    Traverse City, MI
    Posts
    12

    Re: Design for PIM, maximum thickness strictness?

    I second Bryan's thoughts on this subject matter. If you would like to PM me I could give you my email address to possibly aid further.

  4. #4
    Join Date
    Sep 2020
    Posts
    2

    Re: Design for PIM, maximum thickness strictness?

    Thanks much to you both. I'm sure I'll have more specific questions as I get into these projects transitioning from our 3D printed assemblies to injection molded.

    One recommendation, and I don't expect a recommendation really, but if you have any then great. I contacted one large local PIM shop a few times to start a relationship, and no return call, so ready to move on to the rest of my short list. But any recommendation for a shop willing to take on at least a couple of multi-part assemblies for an up and coming so far very successful multi-million dollar startup a few years old? Preferably in the NJ/NYC area, but not required.

  5. #5
    Join Date
    Oct 2018
    Posts
    22

    Re: Design for PIM, maximum thickness strictness?

    I don't have any specific PIM shop's to recommend other then to be open minded to the smaller PIM shops as well. There are a lot of good molding operations, small shops that do everything right because that is how they learned, its the way they teach and it's the way they do it. Big or Small, starting with the basics, is the shop clean and organized? Do they have good documentation or any all. Do the have a quality system in place? And so on. You'll know when you found the right place.

  6. #6
    Join Date
    Mar 2019
    Posts
    13

    Re: Design for PIM, maximum thickness strictness?

    Depends a lot on part shape and gating strategy. Our sprues are often .250" or .375" diameter and mold just fine. But I wouldn't expect to get good results gating into one end of a "flat bar" or "bath tub" shaped part that thick. Certainly the .125" figure mentioned is not a hard limit. We routinely go thicker than that in ABS, PS, PC, ASA.

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