Using Nichrome Wire To Repair Broken Plastic Parts


It’s a real bummer when injection molded plastic parts break. We’ve never found a gluing technique that works for a part which is exposed to force like the clamp on this camera tripod. But [Matthias Wandel] may be on to something. Here he’s using nichrome wire to reinforce the broken plastic part.

The repair process is demonstrated in full in the video after the break. He scavenged the wire from the heating element of broken hair driers. the idea is to wrap the wire across the broken piece, then apply power from a bench supply. This heats the wire, which can then be pulled beneath the surface of the plastic. [Matthias] likens it to using rebar in concrete.

His implementation could be improved just a bit. Getting the wire to embed evenly is a problem, but using a pair of pliers instead of just alligator clips may yield better results.

[via Reddit]

44 thoughts on “Using Nichrome Wire To Repair Broken Plastic Parts

    1. what he said. Rebar goes in concrete for a very specific reason: Concrete doesn’t support tensile loads. The ratio of the tensile strenght of rebar to that of concrete is MUCH greater than than that between (most) plastic and nichrome, and yet you are probably using it in a higher proportion. The Nichrome probably isn’t very well bonded inside after this process either.

      1. A broken piece of plastic also does not support tensile loads. The ratio of the tensile strength of nichrome to a piece of plastic broken in two is nearly infinite. I would say rebar is an apt analogy.

        1. They also put fiberglass in plastic for the exact same reson. Probably the fiberglass is a lot better than the nichrome, but also about 1000 times more impossible to embed in an already-molded piece of plastic.

          I do wonder if you could use the nichrome to weld the plastic back together, it’s probably thin enough to be shoved into cracks in the plastic, then heated and pulled through.

        2. The ability of plastic to hold a smooth piece of nichrome wire is pretty small. So mathematically, you are correct– going from zero tensile strength to weak tensile strength is infinite fold increase. If the wire is twisted with itself to form a hoop around the plastic (like the hoop of a barrel), I can see this as helping. Short of that, infinite, but negligible improvement in tensile strength.

          1. Do you have any evidence to back up your claim that thermoplastic does not bond to nichrome? My experience with plastic sticking to hot wire cutters says that they do in fact stick quite well.

  1. maybe find a method to wrap the wire completely around the two parts, and tighten it using some ceramic or other non conductive, heat resistant material. reminds me of the electrofusion technique for welding plastic pipes together.
    there they have coil of thin wire making many turns.

  2. id use superglue for holding it in place, meldt tracks for normal wire (breathing the smoke ofcourse) and then fasten the wire around it. and then maybe melting some black plastic ontop of the wire to glue them into the tracks

  3. ABS dissolved in acetone and allowed to dry until a thick tar-like gloop remains can be used much like silly putty to fill in broken off bits and then wrapping it around the broken piece as a reinforcing band. It’s self-adhesive and has gluelike properties, and it shrinks as it dries so if you wrap it around it will squeeze the part together.

    Once it dries completely it’ll be hard and tough. I’ve successfully repaired scissors where one of the handles had split off the metal because of too much force. The repaired handle was tougher than the original – the other handle broke off next time.

    1. There’s also a trick you can do with ABS + acetone, if you pour the resulting gloop into water, the acetone dissolves away. Kneading the mass and folding it over and over introduces water inside the ABS and removes most of the acetone, which results in a material that is very much like raw black rubber. It can be rolled into a ball and bounced off walls, or pressed into molds and cooked dry to form objects. The water inside is in tiny bubbles, which expand while heating so it fills molds and diffuses away leaving a porous material that is surprisingly strong and light.

    2. Weld-on is better for ABS. Acetone works but is too fiddly. Less fiddly than futzing around with a bit of wire that’ll fall out after a while, but anyway.

      Or wind cotton around it a few times and coat in superglue.

    1. I’m not sure about ABS plastic but for plastic parts that have broken I prepare a small amount of plastic dust by sanding some hard plastic on course sand paper. I then apply a small amount of super glue to the broken parts and hold them firmly until it sets. I then go over the crack with more super glue, creating a ‘snail trail’ along the crack. While the glue is still wet I sprinkle the plastic dust over it. I repeat this several time letting the glue dry in between applications. This method builds a strong reinforced bond that will hold well.

    1. I too use stainless safety wire in this manner.. heat a small bit with the torch with a slip knot embed it in the plastic and then heat up a bit more wrap it in to the plastic and continue to do so down the object then clip off the remainder when i’m done and it only leaves a tiny nub that can be sanded down a bit.

  4. I have found that melting staples into the plastic across the fracture (after glueing) to be quite effective. The the ability to loop and angle the end of the staple helps anchor the staple so it can take part of the tensile stress (yes it might be weak but it’s better than broken). Example (has in fact cracked again but the staples still hold it together):

    I have had success with a number of headphones that are used regularly.

    Might be able to combine this option with the acetone idea mentioned above…

    1. I think this 6-months later piece of genius may actually save my headphones. I’ve been grumbling about getting a new pair for ages, just cos the plastic band’s snapped by the earpiece. Sure I’ve got some acetone somewhere.

  5. All of these sound messy and time consuming.

    I would just use J+B 5 minute epoxy putty.

    This is the greatest thing since sliced bread.

    Hardens like stone, can drill it sand it, high heat, etc. in 5 minutes.

    Can be molded into any shape in the first few minutes.


    I had a telescoping skimmer for my pool.

    The head of the skimmer was plastic and had a swivel fork joint.

    Half of this had broken off from to much stress(wet leafs).

    Repaired in 5 minutes and as lasted 3 years so far.

    Clean, simple, fast, durable.


  6. Personally, I’d go with the plastic stir welding technique using my dremel. I like the drill and pin approach as well.

    Of course, I’m still in the ‘learn what works’ phase with the welding approach. Certainly wouldn’t work with delrin-like plastics…

  7. goop glue, it isnt completely invisible but a small bead along the inside of a fracture and a little outside of it will be stronger than the original plastic, i glued a small bottle to a microwave door years ago as the handle fell off with no more than a 1/4 inch by 2 inch strip of glue and the connection WILL outlast the microwave, you can be sure of it
    also just repaired a pair of plastic handled scissors with it

  8. Just use some superglue to fixate the part. Then get some solder wick long enough to cover the part. Widen it with a pair of flat pliers so you get a nice wide copper mesh. Then put in on the plastic part and heat it up with your solder iron (don’t use your best tip). It will melt and combine with the plastic giving you a much better support than just a wire. I successfully repaired a lot of plastic parts with that method.

  9. Piano wire by far is the most useful fixer and tool making stuff to have around. I have often bent to shape and solder gun melted pieces of piano wire into broken plastic, kinda like the staples but larger.
    A piece of size 20 (heavy) an inch or two long is ground to a point and inserted into a chuck ended probe becomes number one tool for poking and scribing on ckt bds.
    Don’t ever cut this stuff with regular tools! Or file it. A Vice Grip cutter or string cutter or grind a notch and snap off will work. Or bend sharply back and forth, leaves a nasty end… grind smooth.
    They sell a solvent and plastic powder kit for repairing plastic. Usually on line because of the solvent and huffers. Works great if the solvent is reactive on the sample.
    The problem with huffers means we don’t get to work with real quality glues on the market. Shoe goo when it first came out was hot with good bonding agent. Then kids discovered it’s agent, and now every glue is watered down if not by the Environment Police.

  10. I did not hear in the video if he said what kind of plastic this is, or if he even knew. To me, the significance of this method is that it can be used on plastics that don’t glue well, such as polypropylene and polyethylene (HDPE, LDPE). Good luck gluing those with either superglue or JB-weld.

  11. I like Mathias and his work, but I don’t see why this couldn’t be solved in this simple way:

    1) apply superglue as a temporary fix to hold things together
    2) zip a ziptie around the part. Pull tight.
    3) use some melt-glue or two-part epoxy to make sure the ziptie doesn’t slip off the piece.


  12. Interesting hack, I might have to swipe that idea to fix my car’s broken £270-to-replace indicator stalk…

    Also, the reprap folks might be able to use this method to make reinforced plastic on the fly, by embedding strips of electrolytically pre-cut nichrome in plastic.

    has anyone else other than me thought about making memory plastic, by taking a piece of stretched and trained Nitinol and wrapping it with some of that fishing twine, then embedding it in plastic such as thin ABS?

  13. I wouldn’t use old heated NiCr wire from heaters for this, it could be brittle in places and break easily. As noted new wire is very cheap and if it’s carefully heated only just above the plastic melting point and for a short time it wouldn’t go brittle.

    You could probably use almost any metal wire if your power supply could heat it enough.

  14. Buy a spool of “stainless lockwire” (its normally used for lockwiring bolt heads for racing purposes) from the likes of progressive suspension.
    Heat it to embed it if its in the way on the surface, but use some lockwire pliers to put a tight twist on it. Then you will have a increase in mechanical strength from that also.
    This youtube vid has the concept with the handlebar grips lockwired to the handlebars.

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