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    Discussion in 'Plastic moulding' started by wizardofid, Nov 4, 2009.

    1. kinnavate

      kinnavate Member

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      Hello

      I have engineered many products such as this such as telecom test instruments and cellular phones. I would recommend 30% glass filled polycarbonate. This material will withstand military drop tests and beyond if you engineer it correctly. I drop test instruments from 20 foot high telephone poles to concrete and have had no problems. One time after the telephone pole drop, we decided to throw the unit on the ground and drive a forklift on it to see how good it really was. To our amazement, the forklift drove right up on it and just sat there. There were a few cracks in the plastic and cosmetic scratches, but it survived and worked completely.

      For the LCD I would overmold a silicone isolation gasket in the front housing to absorb shock. The LCD should be covered with polycarbonate and there should be an air gap between the LCD screen and the protective lens. I also recommend that the plastic be built up around the LCD to prevent direct impacts whenever possible. Heavier components on the PCB should be expoxied in addition to soldering to avoid delamination of the PCB. The PCB would also be rubber isolated and conformal coated to provide shock absorption. Overmolding rubber boots or corners can also aid in impact survival. In the units I have designed we also mold in a groove in each size of the housing to accommodate a gasket for environmental sealing.

      This is just a short mind dump but it should give you some direction. I would highly recommend that you minimize the guess & test approach to development. Spend the time to engineer and analyze the design using whatever software is suitable to the task. I would recommend Comsol Multiphysics or Ansys Multiphysics to study the assemblies behavior during an event simulation. You can do this many times in software, improving the design before you commit to costly physical prototyping and testing. Hopefully if done right, you will only need one or two physical prototypes to confirm the predictions of the software.

      Hope this helps

      Kinnavate
       
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    3. DesignTechnologist

      DesignTechnologist Member

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      If you are machining it, you may want to look at PEEK plastic. You can get different types that have glass filled, etc. I've used this for a few different applications. It's expensive but I'd hade it to 4500psi with no problems.

      If you are looking at injection molding, you can get a high impact ABS. I've used this in a recent project and was pretty impressed with it.
       
    4. maniacal_engineer

      maniacal_engineer Well-Known Member

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      If you are going to use PEEK you may as well mold it. Peek has great properties, but is expensive. If you are going to make more then just a couple of them you may as well pay for the tooling instead of paying for chips.
       
    5. Camid

      Camid Well-Known Member

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      We have designed a number of rugged products and we used PC/ABS (GE CYCOLOY) or Glass Filled (as suggested above). Both materials work well and were over-moulded with silicon. Not sure about the MIL spec. We have done ATEX in the past. I suppose it really depends on environment and mass etc.

      Cheers
      Alex
       
    6. wizardofid

      wizardofid Active Member

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      kinnavate, Camid, maniacal_engineer, DesignTechnologist,
      Thanks for all the information. We settled on a 30% Glass Filled PC, with no rubber overmoulding in the current design. We did build a removable sleeve as an accessory for protection in the field.

      @kinnavate: what materials did you use in those mobile phones you designed? Shells vary from 0.7mm to 1.2mm max. Will glass filled PC even fill in those slim profiles?
       
    7. ricky_yu

      ricky_yu New Member

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    8. bfox

      bfox New Member

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      I believe the pc/pbt like xenon would be required over pc/abs due to chem resistant to some of the chemical issues. Both should have the impact performance required depending on the weight and specific drop test for this component.
       
    9. wangyangzhong

      wangyangzhong Member

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      we used to use LEXAN,
      for DELL rugged laptop
       

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