Welding Plastic W/ Soldering Iron




Introduction: Welding Plastic W/ Soldering Iron

About: I am a former Art student, and Industrial Design student. I left school to work on another degree more related to my career. I am still very interested in Art, Design, and Technology.

First off, this was an experiment that ended with effective but unattractive results. I continue to try to experiment and improve the results. Also, please share your results if you try this.

Why: You can glue ABS with ABS/acetone glue , but what do you do for PLA? I had an idea to use a soldering as a welder while looking at a multi part mask print on Thingiverse. Ultimately, a strong weld could be much stronger than the rest of the print due to the larger area of solid plastic. I feel that this will work better than using other gluing methods depending on the requirements of the project.

I printed a case for my Smoothieboard last night that had warped a bit and figured this would be a great opportunity to test this process.

Step 1: Setup and Tools

Tools: Soldering iron with adjustable temperature.

Temperature: I started at 210 because that is what I usually use to extrude PLA. If you go to high, you risk burning the plastic. I ended up going up to 230 to get more heat into the plastic and did not burn it. I haven't tested the upper limit.

Work area: I used my helping hand to hold the project in place but other things could work.

Step 2: Weld Away

The goal of this process is to melt both pieces to be joined and the extra filament all at the same time to fill the gap and create a single piece of plastic.

The initial heat of 210 was not effective. I upped the temperature to 230 with slightly better results. I may test again with a higher temperature. Possibly using a temperature that can burn the plastic but moving fast enough to avoid the burning would work best.


  • 1.75mm filament: I first tried a short piece of filament. The filament was to thick to melt quickly enough. It worked alright when I melted it on to, not into, the seam and then went back and added more heat to the weld area to get a strong weld.
  • Brim filament: I had a piece of filament from the single layer brim nearby so I tried that also. this was a very thin piece and melted very well. However, it was so thin that it was hard to hold straight and took a long length to add enough material to the joint.
  • Ideal? I may try extruding a length from my .80 nozzle the next time i try this to see if that is a better size.
  • 3mm filament. I didn't try but the 1.75 was way to thick so I wouldn't bother unless you have a different iron that can put more heat into the joint or find a better technique.

Results: The part is plenty strong. The welds are a bit ugly. I couldn't get the plastic to flow like with a traditional welder so the joints are a bit ragged.

Step 3: Possible Improvements

I have a few ideas for improvements.

Heated work area: Working with a heat gun or something to apply heat to the weld area would keep the weld from cooling to fast and may allow the plastic to flow for longer.

Preheat: Same Idea as above but preheating the joint with a heat gun and than keeping it warm.

Hotter Iron: I may try a higher temperature that could burn the plastic but keep it moving along quickly to get a better bead.

Larger Iron or different shape head: I have a cheap soldering iron/wood burning kit with several different shapes of heads. One with a flat triangular or teardrop head might work better to apply heat to a wider area. Unfortunately, I don't have a temperature control for that one but I'll see what I can figure out.

If I eventually find a good solution tho this I will make a better Instructible with more definitive guidance. for now this is still experimental.



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    17 Discussions

    Just a thought: A de-soldering iron (hollow element and bit), run from a power controller to adjust the temperature, and feed the filament down the tube ?

    No, hang on, I've just re-invented the 3D printer.

    Has everyone forgotten where the filament for 3D printing originally came from? It was first made as the fillet for plastic welding, the plastic was softened by a hot air blower which later gave rise to the reflow tool used for smd circuits.

    2 replies

    I could see having a hot air rework station might work a lot better for this process. Unfortunately, I don't have one at the moment but its on the wish list.

    I treated myself to one a couple of months ago because I needed to repair a laptop hard drive, got it off ebay for £60 but that was one of the fancier ones, the standard ones are about £30 if you look for them.

    If you just want it for welding then a hair drier might do it depending on the type of plastic being welded or a hot air gun will definitely do it, all cheaper than a rework station.

    Hi - had been throwing around this concept after seeing the great results of a friction welder - any thoughts?? - - ha!, if you can understand my dodgy drawing, been a while since I was in the drawing office.

    4 replies

    Cool Idea, the spinning bit at the end might be hard to build. I had a few ideas for devices as well. My friction welder idea would be to use a dremel with a small stone bit. Then have some sort of adapter to push filament through so it come out right at where the bit meets the welding surface. Then you could have a Bowden extruder pushing filament to this adapter. You could probably have an adjustable feed rate like a wire welder. I don't know if this would work or not but I think if the bit was spinning fast enough and the filament was held close enough it might work.

    I also was thinking that using a 3D printing pen or Bownden fed hot end with the soldering iron might make a better solution.

    Unfortunately, I don't know when I would have time to try any of these.

    The spinning head - ya know, I was thinking, how about a jewelers or small machinists pin vice - like a chuck crossed with a precision screwdriver, if I remember rightly they have a hole from front to back and a long (ish) shaft that some mountain board bearings could slip over, fabricate a handle to encompass the lot and it might work a treat.
    Oh! I really like the idea of a power fed filament.

    soldering irons work ok but ya have to be so careful with the heat, to hot and the plastic and join are ruined as the oil burns off, the weld is brittle and though may look really tidy but if ya load it in even a small way it is prone to fail - that was why I really liked the friction idea, cold to the touch until the spinning tip touches the surface.

    that stone bit sounds like a good idea - interesting!!!

    tricky stuff to weld - have done it but your right, ya need the heat and speed to be synchronised so as not to burn it.
    will follow your posts, see how ya get on.

    2 replies

    Thanks, I'll try to keep it going with some more tests.

    Will be cool if ya get this sorted - there are tools out there, but for the home builder the technique is often hit n miss.
    The friction welding idea posted is interesting, I had forgotten about that - if only there was a way to extrude the filament.
    Don't know if this will be of interest but on F/B there is a group PROTO - TYPE - CHAT, it would be great if ya popped over and maybe said a little about what drives your projects, maybe keep us all up to date on your welding progress, to get this sussed would help out on so many projects.

    Try friction welding it works better. Take a dremel tool and put filament in where the bit should be. Make sure the filament is straight so it doesn't wobble. rev it up and touch the part you want welded.A puddle will form push it across like you are steel welding and BAM!!! welded.

    3 replies

    And then you stop a half inch later and reload your filament since shorter sections of filament are necessary. If doing a lot of welding with friction, the major time sink is unloading the stub and loading another inch of filament. (can you tell I don't like friction welding? ;))

    If this can do something similar in half the time, I'm willing to try this instead.