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  • Screw/Threaded connection

    Discussion in 'The main mechanical design forum' started by test1screwdriver, Mar 13, 2014.

    1. test1screwdriver

      test1screwdriver New Member

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      Hello to all

      I am fresh to plastic part design, especially regarding the about the ways parts should or could assemble each other.

      At this particular moment I am most interested in screw/thread joints, like a cap for the bottle, cover, or two parts assembled togheter by "screw joint". By this I do not mean parts joint by screws - > http://www.pencomsf.com/category/screws/screws-for-plastic/

      I can find the mechanical equation for this issue but I missed general info.

      Can you tell me what, where and why?

      * Which type of thread fits best for plastic application?

      * how to develop best number of rotation for "nut part"?

      * what should be the height of "nut part"

      please follow thread types introduced in attached picture

      thx in advance

      [​IMG]
       
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    3. dgerbs

      dgerbs New Member

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      Hi,
      Unfortunately your questions are too open ended to realistically answer them. All of the thread forms shown in your image can be manufactured in plastic. Which thread form is "best" depends on the application of the product.

      The best way I can answer your questions is with more questions. When designing threads in plastics, you need to consider:
      • Which plastic is being used and are both female and male threads of the same material
      • What manufacturing method will be used? injection molding, roto-mold, machined, vacuum formed, etc
      • what loads will the threads experience
      • are there requirements for the number of rotations from engagement to tight?
      • Will the threads seal against leaks or only for mechanical attachment?
      • and there are more depending on how these questions are answered

      I hope this helps you
       

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