Epoxy for Winding Solenoid?

Discussion in 'General Electronics Chat' started by scubasteve_911, Jan 10, 2008.

  1. scubasteve_911

    Thread Starter Senior Member

    Dec 27, 2007
    1,202
    1
    Hi All,

    I am winding up a solenoid that needs very precise layers. I have a predefined form for the first layer that will accomodate x amount of turns of my wire. I want to brush on a thin epoxy and let dry, then wind the next layer. I want to continue this until I have seven discrete layers, which will be paralleled in the end.

    Can anyone suggest an epoxy for something like this? I guess it needs to be thin enough so that it doesn't cause the next layer to be all over the place. I want the wire to stay put and adhere to the below 2mil kapton film.

    Any ideas?

    Steve
     
  2. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    Have you thought about cyanoacrylate (Super Glue)? If it won't dissolve your insulation, and will adhere to it and to the Kapton, you can get it with water-like viscosity, and it sets up in 30 seconds or so.
     
  3. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Use a "laminating" or "finishing" epoxy. Do not use "adhesive" epoxy. Thin no more than 1:3 with denatured alcohol.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    I suggest you use something other than Kapton insulation.

    It breaks down under exposure to concentrated alkali, it's hydrolitic (absorbs moisture), tends to wander around, and arc. When it breaks down during an arc, it turns to a flammable conductive carbon charcoal, which can ignite explosively.

    The U.S. Navy banned the use of Kapton insulation in it's aircraft in 1987.

    Here's some reading suggestions:
    F. J. Campbell, "Temperature Dependence of Hydrolysis of Polyimide Wire
    Insulation," IEEE Transactions on Electrical Insulation, Vol. EI-20 No.
    1, February 1985.

    A. M. Bruning, "Predictive Life Measurements of Naval Aircraft Wiring,"
    Proceedings: Workshop on Power Plant Cable Condition Monitoring, EPRI
    EL/NP/CS-5914SR, July 1988.

    And from the NRC: DEGRADATION OF KAPTON ELECTRICAL INSULATION
    http://www.nrc.gov/reading-rm/doc-collections/gen-comm/info-notices/1988/in88089.html

    An airline pilot's research on the subject:
    http://www.vision.net.au/~apaterson/aviation/kapton_mangold.htm
     
  5. scubasteve_911

    Thread Starter Senior Member

    Dec 27, 2007
    1,202
    1
    Thank you all very much! Superglue seems like a good solution, but I wonder why 'finishing' epoxy is a better choice according to thingmaker. I saw an employee use some sort of thin epoxy on voice coils on the show 'how it's made', but they didn't mention much about it.

    Wookie,

    I didn't know Kapton had major flaws.. It's too bad that I had purchased a big roll of it, eventhough I plan on using it for other things. I was planning on coating the stator with some sort of enamel, but nothing seems easy to apply. It seems like a special process to coat stators, which is what I want to avoid. I heard of someone using stuff called 'gun kote', but I'm a bit reluctant to use products that feel the need to spell their name with a k to sound marketable :p

    Steve
     
  6. scubasteve_911

    Thread Starter Senior Member

    Dec 27, 2007
    1,202
    1
    Wookie,

    I am not sure, but I think I wasn't clear about my use of kapton film. I'm using 2mil Kapton MT film (thermal conductivity type) to line my silicon steel laminations. Then, I plan on winding my coils, layer by layer. Each layer will be secured via painting on thin epoxy or superglue.

    I'm using regular 200 degree 23awg wire, 28 turns per layer, 7 layers. I designed the bearing so that I can lay down exactly 28 turns of coated 23 awg. I alloted 0.2" for the 7 layers, eventhough it should be less than 0.025" X 7 = 0.175.

    Steve
     
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Steve,
    Just wanted to make you aware of it. Kapton has some remarkable qualities, but there are caveats that one needs to be aware of.

    I'm kind of old-fashioned (in many ways) - you might consider wrapping the core with Teflon tape on top of the Kapton. You can get conformal coat in spray cans, it goes on quite thin, but takes a good while to dry. Many of them are acrylic lacquers. Conformal coat is used on most military specific boards to protect them and keep the components in place.

    But there may very well be newer/better/cheaper things out there.
     
  8. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    I'm not saying that finishing epoxy is better than cyanoacrylate. I have no experience with cyanoacrylate. The finishing epoxy is better than the adhesive epoxy (in this application) because of lower viscosity.
     
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