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  • What material should I use?

    Discussion in 'The main mechanical design forum' started by Andy Haard, Jul 7, 2012.

    1. Andy Haard

      Andy Haard New Member

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      Hi
      I need some suggestions on what material to use, hope you guys can help me.
      It needs to be an electric isolator, as rigid and stiff as possible without being brittle.
      I must be able to drill holes into it and put some pressure on it without it cracking and it needs to be as durable in -40 C as in +80C. I will use it in bars 8mm thick by 15mm wide and in length of about 180mm
      /Andy
       
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    3. SCIYER

      SCIYER Well-Known Member

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      Phenol-formaldehyde (common trade name: Hylam) with fabric bonding. Comes in three grades of Fine, Medium and Coarse grades of fabric. The below link should help.
      http://www.bakelitehylam.com/indlamni.html
       
      Last edited: Jul 8, 2012
    4. vic.blackall

      vic.blackall Well-Known Member

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    5. SCIYER

      SCIYER Well-Known Member

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      The link given by vic.blackall would be more appropriate if you are from UK. I being from India, gave a link that is local to me. I am sure you must have got the idea.
       
    6. ced53

      ced53 New Member

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    7. Mark Stapleton

      Mark Stapleton Active Member

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      Although you have not specified the voltage or the operating conditions or environment other than temperature (chemical exposure? UV exposure? marine environment? mechanical stress?) PTFE (polytetrafluoroethylene), commonly known as Teflon, should fill the requirements well. It withstands much more extreme temperature conditions than you mention, is quite rigid, is easily machined, is UV resistant and is not brittle. In addition it is more chemically inert than any other plastics of which I know. There are many other plastics which would do almost as well and are much cheaper. If chemical resistance is a requirement then think about UHMW (polyethylene). If not think about acetal copolymer (Delrin II) or PEEK. If you don't have an extreme requirement for electrical resistance then your field of potential choices widens considerably. If no UV exposure think about PVC (there are also UV stabilized formulations) or ABS or polycarbonate or PET or polystyrene or Nylon or polyurethane or polypropylene or about half a dozen other plastics. For further information consult www.matweb.com and www.mcmaster.com. The former is to reference physical properties. The latter is to determine costs and do a rough comparison otherwise.

       
    8. Andy Haard

      Andy Haard New Member

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      Hi, thanks for the suggestions. Other important criteria is that it's light and cheap.
      The bars will be pressed together, the 15mm sides against eachother, 75 of them. Between each pair will be two thin alu tabs, pressed together.

      It is for building battery packs for these cells:
      http://blog.evtv.me/store/proddetail.php?prod=123
      The idea is to have three stainless threaded rods running though all 75 isolators with bolts at each end and compress it all together. It is to go into a car so it must be able to handle vibrations and temperature.
      /Andy
       
    9. Mark Stapleton

      Mark Stapleton Active Member

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      Once again, you seem to be either in the dark about what you are actually trying to design or else you aren't specifying extremely important criteria. In designing a battery pack you will doubtless have this plastic in contact with some chemicals ... typically very corrosive materials (as most battery chemicals are). Do your research. What are you dealing with? The quality of your responses are very highly likely to be in direct relation to the quality of your question.

       
    10. Andy Haard

      Andy Haard New Member

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      No chemicals, sealed prismatic pouch cells (LiFePo4)
      I'll probably use G10/FR4 for the isolators, see this animation:href="mh9fptEnvcM">
      My concern though is if pressing the isolators together using 3 M8 threaded bars will create enough pressure to secure the connections between the battery tabs in the long run in an automotive environment...?
      Any taughts on that?
       
      Last edited by a moderator: Jun 17, 2016
    11. vic.blackall

      vic.blackall Well-Known Member

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      You will need to watch the tolerances of the spacer parts in order to obtain pressure between the battery tabs.
       

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