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Thread: Plastic Welding

  1. #1
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    Default Plastic Welding

    For all those that want a cheaper alternative to commercially plastic welders, here is a couple of things that can be done to make your own.

    Most people already have just about everything you need if you have a propane torch or a 80W soldering iron to weld plastic.

    With an 80W soldering Iron, place a carriage bolt where the tip was and melt away, use the same type of plastic as you started with to provide the bond. I do this on canoes all the time and it has worked flawlessly.

    With a propane torch, get a 4" piece of 3/8" tubing, a 3/8 pipe to 1/4" flared fitting, small hose clamp (1/2" diameter clamping range) and 4" of 1/4" brake line from any auto supplier. Take the 3/8" pipe and grind or cut a notch on each side (opposite each other) for a length of 2-1/2" to 3", then assemble the brake line to the steel pipe (after cooling). Place notched end over the torch tip (before lighting) and clamp into place.

    Weld away! Both work as well as commercially available units and can be made for much less.

    HTH Will follow up with photos of the propane unit later this weekend.

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    Member markopolo50's Avatar
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    Can you show a picture of the torch setup? I can't quite follow the "assembly". Thanks. We have used a propane torch to repair windshield washer bottles after freezing/splitting. Torch flame was "feathered" as butter dish plastic was added. Worked for us and of course nothing under pressure.

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    Would love to see a photo of that myself.
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    Default Pictures

    Sorry about the delay. I wanted to get these up over the weekend, but was called to work in a bush village. Just got back last night and didn't have my camera with me while I was out there.

    Here's a couple pictures of the assembly, hope they help clarify what I was describing above.
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    Default Pictures part Duex

    A couple more pics.
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    Member markopolo50's Avatar
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    Default Torch pics

    Quote Originally Posted by blybrook View Post
    A couple more pics.
    I can see it now, clearly, thanks blybrook. The torch heats up the whole pipe assembly, nice. Mark

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    Quote Originally Posted by markopolo50 View Post
    I can see it now, clearly, thanks blybrook. The torch heats up the whole pipe assembly, nice. Mark
    Yes, the whole pipe assembly heats up. The notches that are ground in, permit it to fit over the torch nozzle and to dissipate the heat so it doesn't get too hot. It also creates a heated air stream like the harbor freight models that require an air compressor.

    It does get hot, so it'll need a while to cool down, but I've used it on two different projects so far and does a better job than the harbor freight unit. Less noise too.

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    Default Plastic welding!

    Here's another gun set-up...I use a heat gun with a reducer and a few other attachments. One is for speed welding and the other spreads the heat out.. here's some of my projects.. I'll see if I can find a picture of my heat gun..
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    Default more pictures

    Finished product
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    Default Gun boot

    I wanted a smaller gun boot to mout on my bike rack.
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    Default Plastic welding!

    Boot on the bike... can't find a picture of the heat gun, I'll take one tonight..
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    Member JOAT's Avatar
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    Interesting work. What's your experience with the longevity of these repairs? Do you tend to get recurrence at the site of the original break? Or does the recurrence occur next to the original break?
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    Moderator Paul H's Avatar
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    It depends on if the break is due to an impact to a part that exceeds the design for the part, or if the part is incorrectly designed, also if the core plastic is still good.

    What I mean is, if the part is poorly designed and fails due to stresses occuring where the part fails, it will likely fail at the same spot. But, the folks I got my plastic welder from include some stainless steel screen that you can melt into place in a repair that strengthens the joint.

    If the plastic is shot from UV exposure (one fender on my boat trailer) then it's just going to keep failing after welding as the plastic is hardened and filled with mini cracks.

    In general you can get alot more life out of plastic fenders at al by welding them back together, and the repairs are pretty much limited by you finding all the pieces, and how much frankensteining you want to do by sticthing them together with safety wire before welding.

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    Default Plastic welding!

    Here's a picture of my gun with attachments.. I spent about $100 on it.. I spent most of it on the gun because I wanted one with good temperature controls..
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    Default Plastic welding test

    Here is a test... I welded 4 brackets on a box last spring to use as a 4-wheeler box. This winter while 4 wheeling I broke the box and decided I didnít need it anymore. I took a screwdriver and jammed it between the bracket and the box and pried on it try to make it break through the weld.. Both brackets I tested broke and the weld stayed..
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    Default Plastic welding test

    Here is the back of the box, in the top corner is where the box broke, I attempted to fix it, then decided it wasn't worth the effort.. I welded the box once only to have another crack form on the other side.. what looks like a weld at the top is where I was heating it up and tacking it so I could weld it..
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    Here is how I repair my Plastic water Tanks for the horses. You can use any style of torch, I prefer a simple 1 lb propane bottle with a torch on top. Heat the plastic around the crack, not too much, just enough to make it melt, and quickly with a metal tool like a trowel, scrape the melted plastic across the crack. I keep doing this from both sides of the crack until it is sealed. It has always worked for me, and holds water. Don't know if this will work for your application, but thought it couldn't hurt.

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    Thanks for the nice write up, I'll have to try this sometime.

  19. #19
    Member ironartist's Avatar
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    Quote Originally Posted by delta2185 View Post
    Here is how I repair my Plastic water Tanks for the horses. You can use any style of torch, I prefer a simple 1 lb propane bottle with a torch on top. Heat the plastic around the crack, not too much, just enough to make it melt, and quickly with a metal tool like a trowel, scrape the melted plastic across the crack. I keep doing this from both sides of the crack until it is sealed. It has always worked for me, and holds water. Don't know if this will work for your application, but thought it couldn't hurt.
    I like your rudemetary plastic welding it sounds like me. The only thing I might do is cut a bit of filler off an unneeded area and make my weld area a bit thicker. I've plastic fused many things togather just with my glue gun and my heat gun to preheat the entire area, works great
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  20. #20

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    I had a saw shop for 7 years and we would weld tank housings all the time. It was the only permanent fix there was. The epoxies that guys tried just did not work.

    A couple things I learned when doing this.

    #1 Do not get the plastic too hot as it will cause it to become brittle.
    #2 If you need filler plastic, make sure it is the same type. If you can cut a piece from the material you are welding.
    #3 If you can not cut a strip form the piece you are working on then you need to do a burn test. Take a small piece of the material you are working on and watch the flame and soot that comes off of it after you light it on fire.
    There are many different types of plastic but what ever you want to use as a fill piece (or filler rod) needs to be the same type so do a burn test on the sample and make sure that the flame and soot matches the first burn test.

    I used a straight soldering iron most of the time. I went and bought one of those fancy hot air plastic welders, but it was more of a pain in the but and just never really used it much.

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