Played with my new air-powered plastic welder

**thebigthn** · 05-17-2009, 07:47 PM

Hi everyone,

I've been reading up on turbocad6's sticky on fabricating a bezel. After seeing the AMAZING job he did on his infinity with a plastic welder, I decided to buy my own and check it out.

I've never welded anything in my life before, but I figured plastic's probably an easy enough material to start with. I bought one of these:

<See first picture>

and some cheap plastic bins and hangers from the dollar store for practice. I figured I'll try and get the hang of it before I start messing with my own radio bezel.

Results:

I think an airless welder would be easier to work with. I had a problem with the air blowing the pieces out of shape even when I turned down the pressure . Also, the finish isn't quite as smooth as I though it would. Maybe because I didn't have anything smoothing out the hot plastic as it cools.

What do you guys think? I read that a soldering iron with a broad tip would work, so I might buy one of those. Also, soldering irons are cheaper than an airless plastic welder and with more uses.

Also, I never tried to bondo or use plastic filler before either, so I'm not even sure if plastic welding is easier or not.

**Nexson** · 05-17-2009, 08:48 PM

Hey

Looks interesting, What exactly did you weld?

Don't expect it to look pretty. The welder is meant to mend the pieces together, then sanding and filler follows.

How is the mend, are you break it off with some presure, or is it actually melted together?

**stealinfool** · 05-17-2009, 08:51 PM

Don't give up yet. I have the Urethane supply airless version, and even with that it takes some practice. You've already spent the money, why not see if you can make it work?

If not, I'll take it

**thebigthn** · 05-17-2009, 09:48 PM

Originally Posted by Nexson

Hey

Looks interesting, What exactly did you weld?

Don't expect it to look pretty. The welder is meant to mend the pieces together, then sanding and filler follows.

How is the mend, are you break it off with some presure, or is it actually melted together?

It's just a plastic case I bought from the dollar store and some plastic hangers. I just cruised around the place and looked for anything made of plastic. I figured some nice flat pieces from the case and the rods from the hangers would work. Total cost of material = well, you get the idea.

Oh, and it's actually pretty durable. It takes some pressure to snap apart. I'm sure if it was real ABS plastic or something it would be even stronger

**rdholtz** · 05-17-2009, 10:27 PM

I tried hot air welding with what appears to be the same unit you have. I thought the results were interesting, but just not something I'd accept for the bezel work I wanted to do. I read more, and ended up with the same sort of welder that turbocad6 has. Urethane Supply sells the KC Welder and the KC Welder Pro. I bought the Pro version. The guys at Urethane Supply were helpful and knowledgeable and, it turns out, right on target with their recommendations. I've been very happy with the results, and would suggest you give their stuff a look.

Where the hot air welder seemed like a great idea, it failed in execution. The KCWelder Pro, on the other hand, has been terrific. It took a while to get used to it, and I made some pretty lousy welds at first. But my welding with it now is just fine; we just welded up a water tank that was leaking, and you can only barely even see where I welded. It hasn't leaked a bit since I welded it.

One thing to be careful about is that you weld similar plastics. Be sure you identify the bezel material you have, and only use filler rod of that same material. If you call Urethane Supply and tell them what your bezel material is, they'll guide you.

And, if you get the "soldering iron" type welder -- like the KC Welder -- use it outside with lots of ventilation. The fumes are very toxic, and plate themselves permanently to your lungs. I use two fans in the garage when I weld, both pulling fumes away from the welding area. DON'T breathe that smoke.

Despite that precaution, I think you'll really like the results you get -- way, way more than the results with that little hot air blaster.

**mreish** · 05-18-2009, 07:48 PM

This is from a friend of mine:

Check out “Getting Started in Welding Plastics”, Glenn Vandiver, Home Shop Machinist, May/June 2004, pages 44-51 for some hints. A big hint is to pick up a “router speed control,” often on sale for $12.50, regular $25 from Harbor Freight, so as to be able to regulate the heat while maintaining a reasonable air volume. Otherwise, the only way to regulate the heat is by varying the air flow, which is not optimal or fun.

The “trick” seems to be to get the temperature just right. There are some big differences between metal welding and plastic welding. Thermoplastics are poor heat conductors, so the filler rod may not even thoroughly melt–in even a good weld, the rod can look unchanged, though the material on either side of the weld should look melted. There is a narrow range of viable temperatures too–just a bit too much heat at one point can char or burn the plastic. In general, plastic welding is not about having the materials flow together as a liquid, but fuse together in a “plastic” state. A proper joint can be up to 90% as strong as the original material. In general, most any joint type normally done in metal welding is possible with plastic welding.

See also Kamweld.com website, especially their article “Plastic Welding Using Kamweld’s Durable Welders” (see under “Resources”).

*NEVER* let the air pressure drop to zero–there is no protection built-in, and the welder will catch fire. When you are done using it, just let the remaining air in your compressor tank flow through (or if you have a Big Tank, until everything is cool).