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plastics electronics crack

Discussion in 'General Electronics Discussion' started by gamer87, May 11, 2019.

  1. gamer87

    gamer87

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    Mar 11, 2017
    Which product to use to repair definitely electronic plastic parts with cracks?
     
  2. AnalogKid

    AnalogKid

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    Jun 10, 2015
    Your question has zero useful information. What parts? What cracks?

    Photos?

    ak
     
  3. Bluejets

    Bluejets

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    Oct 5, 2014
    Appears to be some type of mounting , no "glue" that will fix that successfully.
    Only option I can see would be to use longer self tapping screws of the same gauge.
     
    davenn likes this.
  4. dave9

    dave9

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    Mar 5, 2017
    Looks like those are to attach sockets to a chassis back panel, yes?

    First, use cyanoacrylate glue (aka Superglue), the thin type not the gel type. Apply sparingly into each crack, and use a C-clamp to hold it together until it dries. This is just to return the piece to the original dimensions without extra play where the screw, screws in.

    Next get a round piece of plastic of larger diameter, for example the body of a plastic marker, or a piece of PCV plumbing pipe, etc. with the end of it plugged.

    You want to slide that over the cracked piece, as a shell around it with an air-gap in the middle. The end of the shell should be flush with the end of the cracked piece, where it screws to the chassis. You will seal the end with masking tape to form a leak-proof barrier. The other end of the shell should be plugged so it is also a leak-proof barrier. The bottom of the shell should be taped to the cracked piece, also forming a leak-proof barrier.

    The top of the shell should have a large hole or a split portion. You are essentially building a tube around the cracked piece with the only way for liquid to get in or out is through the top from gravity.

    Into the large hole or split portion, fill it with slow set epoxy.

    Another alternative is put in a very thin layer of epoxy then lay fiberglass cloth around the perimeter, coat that with more epoxy, through another layer of fiberglass mating on top, and coat that with epoxy.

    Another more permanent (can't be disassembled again later without much frustration) is reassemble the whole thing into the chassis but just before you screw the screw into the cracked portion, fill the whole with epoxy then screw the screw in, then let it set for a day.

    Another option, forget about those PCB mounted jacks. Get panel mounted jacks, mount them to the chassis, then connect them to the PCB with wires.

    Another option, make a back-plate that sits behind that vertical jack assembly and extends past both sides of it. Put two additional holes in the chassis wall and run long screws through the chassis holes, into the backing plate behind the jacks.

    Another option, leave those jacks there but unused. Run jumper wires from their solder points on the PCB to a different location where you mount panel mount jacks in new holes you drilled into the wall of the chassis.

    Another option, if the outer barrel of the jacks is at chassis ground potential and the chassis is metal, solder them to the chassis wall, or if there is clearance to still get the jacks inserted, after protruding from the chassis wall, slip thin washers over the sockets and solder those to the socket outer barrel metal.

    Another option, use a very long bolt and put the bolt all the way through the cracked piece and secure the bolt behind the cracked sleeve with a nut.

    I'm sure there are other methods but surely one of the above will work. ;)
     
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  5. gamer87

    gamer87

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    Mar 11, 2017


    is normal or abnormal appears these crack at the screw local? all of these treatment options which way do you consider the simplest, easiest, cheapest and who definitely repair these cracks? I need something to penetrate the narrow cracks.
     
  6. dave9

    dave9

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    Mar 5, 2017
    Penetrating the cracks is not a long term solution, would only serve to hold the material together in the right diameter for the screw while you either fortify the surrounding plastic with an overmolding (filled with epoxy was my suggestion) or to mechanically fix the socket from the front or rear.

    There is no way to just mend the crack itself and make it stronger than the original material which obviously was too weak or else it would not have cracked. Granted an error at the assembly factory could have over-torqued the screws or poor packaging material could have caused a bump against the side of the box to stress them, but ultimately you are looking at one of several methods to additionally fortify what is there.

    Which way is easiest depends on your experience working with epoxy, having materials to build a shell around it, or having a piece of plate metal to put behind it, having sufficiently sized screws or buying some, or willingness to drill new holes in the chassis and buy panel mount sockets if you don't have any, etc.

    Perhaps I listed too many options but there is more than one way to skin a cat. ;)

    Since I have some epoxy, I would get the body from a magic marker, make a shell around it, seal off both ends and the bottom where it meets the existing plastic so none leaks out, and fill the top with epoxy after having superglued the part together with clamps first so it was the correct diameter. It may be easier to do it (with experience) than to describe it.
     
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  7. gamer87

    gamer87

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    Mar 11, 2017
    It is difficult because the cracks do not have openings the cracks are joined I need a product that enters the crack and permanently paste the plastic so it never breaks when putting and removing the screw, a friend oriented me silicone liquid, you gave me these options but I'm confused which option to choose to fix permanently, the screws I use are TV original

    [​IMG]
    https://uploaddeimagens.com.br/imagens/img_20190509_093734727-jpg
     
  8. Ylli

    Ylli

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    Jun 19, 2018
    These almost look more like scratches than cracks. How did these cracks occur? Did you try to install oversized screws? Otherwise, I have had RCA assemblies like these strip out, but never actually crack (they are used all over in audio equipment). If the holes are stripped out, using the same size but longer screws might be the answer, though finding these M3 sheet metal screws can be difficult.
     
  9. Martaine2005

    Martaine2005

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    May 12, 2015
    I agree with ALL of the replies.
    Except nobody has mentioned whether or not these mounts are 1980s brittle plastic. It just keeps breaking!.
    As suggested already, I would sleeve the mount but with thin brass hollow rod epoxied in place. Also epoxy the screw hole and insert the screw. After two or three hours carefully and slowly remove the screw. Leave area to cure over night. It should now be stronger than new.
    upload_2019-5-12_9-40-55.jpeg
    Martin
     
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  10. gamer87

    gamer87

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    Mar 11, 2017
    I do not have bronze rod I want to permanently close these cracks
     
  11. Ylli

    Ylli

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    Jun 19, 2018
    The only chance you have to permanently fix these is to solvent weld the cracks. That would mean you would need to know what type of plastic it is. Then you would need to slightly expand the cracks so the solvent would flow into the crack, then find some way to clamp the crack back closed.

    Alternately, you could replace the RCA socket assembly.
     
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  12. gamer87

    gamer87

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    Mar 11, 2017
    Socket rca is no longer for sale here do not think it used, I would not like to open more plastic cracks
     
  13. davenn

    davenn Moderator

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    1,705
    Sep 5, 2009

    go to a hobby shop and buy the appropriate size :)
     
  14. FuZZ1L0G1C

    FuZZ1L0G1C

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    Mar 25, 2014
    Q-Bond is a superglue liquid & re-enforcing powder (aluminium or plastic) kit to mix as required.
    Car spares and hardware shops may keep it.
    Slowly build up a rock-hard shell around the posts by alternating superglue and powder.
    Epoxy putty (the one that you mix) will also work, as long as a thick wall is built up.
    Another tip:
    When re-assembling a device with these self-tapper type screws, try to use the same thread pattern (shape) that is already in the hard and brittle plastic post, otherwise trying to "force" a new thread may very well crack the post.
    A standard trick is to turn the screw in an anti-clockwise direction until you feel it 'bump' forward slightly, meaning it has seated properly.
    Then place a drop of oil or grease on the screw thread near tip before screwing in.
     
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