Anyone good at with a plastic welder? (and tig)

[Blake]

Hey everyone,

On the way home from work today i stopped at the book store and picked up a book on rochester carbs for my caddy when i came across a "how to weld plastic" book. which got me thinking, one of the mounting tabs on my caddy's headlights broke off and it needed to be fixed.  so needless to say i went to the harbor freight store near by and bought a plastic welder for 25 bucks (it was on sale) and went home and started fiddling around.  i didnt have much time since it was almost dark by then and i tried "welding" a plastic bucket i had.  i THINK it was pvc, but not sure, because this was the first time i ever tried plastic welding and nearly melted through the side of the bucket (i have no clue how to weld)

I also picked up some welding rods of pvc, abs, and nylon rods.  But i also thought this would be a good tool since some of my side panels on the vision are cracked, and also my shark fairing has a nice stress crack in it that could be welded up.

I was wondering if anyone had any experience with plastic welding and could give me any tips (how do i know what type of plastic it is) and most importantly, just the basic of how to weld.  I know how to weld metal but this seems completely different.

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=41592

thats the welder i picked up today.

Also!
While there i was looking at the real welders and i almost crapped my pants!
there was a tig welder on sale for $200!
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=91811

Granted, its not a $2,000 monster, this said its range is .05-.110" thickness.  Exactly what i would probabaly use it for (maybe gas tank repair. and definately for exhaust welding)  It looked decent enough for the price.  All i have now is a wire feed welder and that thing is messy as hell.  I was wondering if anyone with welding experience, do you think this would be a somewhat decent tig welder to start with? (like i said, dont want to weld anything huge, mainly some thin sheetmetal and exhaust items, and some aluminum stuff, and definately will have to learn).  but for 200 bucks thats a hell of a deal for something thatd id use a LOT if it does its job.  it has the tig torch (also a arc torch), and has voltage adjustment on the box (i bet i could construct or rig a foot control to ease) and has gas adjustment on the torch.  but just wanted to see what someone else thought before i go drop money on it and a tank of argon (you use argon for it right?).


Just some random inquiring so maybe i could fix some vision parts of mine.


thanks

Blake

[Mutt]

Maybe you have a spare YICS unit laying around to practice your new gizmo on. For 29 bucks it would be worth it for all of us to have one.

[Koaps]

If Im not mistaken your plastic welder is not much more than a smaller version of a shrink wrap heat gun.

Just hot air to soften and join the plastics together. I'm sure you don't want to melt the plastic but only heat it til gets a bit of a wet look(smooth and shiny) on the two pieces and then press them together.

The method isn't very effiecent, lots of heat loss and not a strong bonding, I believe there's an ultrasonic method for joinning plastics thats far more effective and probably a lot more bank.

It will also greatly depend on the plastic rating(I'm sure anything from 1 to 5 will melt ok, 7 and higher will probably not bond right, but I dont really know, I pretty much stick to ARC with metals and dont work with chemistry of polys.

Try cutting up a bunch of different types of plastics and see which wetten correctly, and which just melt or wont wetten at all.

If you want to use fiberglass and resin to fix stuff, I've done lots of work there repairing surfboards. ?;D

[jasonm.]

I use Devcon Plastic welder from WaMart. At $2.29 each...this is the strongest stuff I have ever seen or used. It takes just minutes to use.

[Riche]

Blake

I?ve used a plastic welder. It?s like a hair dryer on steroids. You just heat the plastic until it?s soft enough to stick together with the filler rod. Get it warm and lay em in. Standard PVC pipe is all that I?ve successfully welded. Most of it was 10? pipe and lots of layers of filler rod were used. To much heat and the plastic will burn/blacken. They don?t melt together in a smooth bead because you don?t draw a puddle like in welding steel. A try to repair an outboard gas tank was unsuccessful. It seems only some plastics can be welded. As Koaps said the joint is weak.

That type of tig machine is something I?ve very little experience with. The high buck machines with foot control yes but that looks like the scratch start type. That type I used once and didn?t like it much. If you plan on welding Al I don?t think scratch type is a good way to go but could be wrong. Welding Al or steel with a treadle makes it easy. You can cool the puddle with the filler rod and/or treadle. Undercut is easier to control with these two options combined with speed and arc length.

Disclaimer (LOL) Riche is no expert welder. My vision limits my success. If you can?t see it you can?t control it. Wait for some of our welding pros to respond before you make a decision.

[Koaps]

I'm going to back Riche on the scratch thing only because I finished my first semester of welding and stick is not only ugly and messy but being phased out to wire feed process of MIG.

I can say from what I have read on MIG/TIG power supplies and circuits used that a foot petal on TIG is practically a must. The circuit is designed to change a sine wave to a saw wave with the introduction of a controlled square wave, IE as you push the petal you increase the power to the arc, thus you can have a refer arc and a welding arc all at the control of your foot, big plus in my book.

Since I haven't yet done TIG I can't offer much(next semester ?;D ), but if you want to see some ugly stick welds, look at my work:

http://angrypacket.com/~koaps/mach/mach130.html

[Koaps]

BTW,

Did you notice that welder is 220v and only 35% at 130amps.
The $2000 monster you mentioned before(like the ones in class that do it all) are 100% duty cycle.

One thing my teacher warned me about is the duty cycle of cheap welders, always check them.

[Blake]

Thanks for the info everyone.

Today i stopped by boarders on the way home and "browsed" the automotive books and looked at a book about welding and it happened to have plastic welding in it.  was really helpful.  needless to say i had no reason to buy the book after that :)

anyway, went home and made a decent plastic weld on an old cracked side panel (left side), i assumed it was abs and so used that rod, but after grinding it down after, i was able to pull it off after..either i didnt melt the surrounding area enough or it wasnt abs and didnt stick.  oh well.. ill play more tomorrow.


Riche and Koaps,

I was checking out that welder some more, seems its straight dc so no aluminum, and after reading some pretty much its crap (like i didnt already know that). the whole reason it caught my interest is in a few weeks im going to be redoing the exhaust on my 76 caddy (have to make my own headers because no one makes them for the car/engine-500cui).  But just thought that maybe a cheap tig welder would help save me a few bucks with the welding.  but now that i think about it, im thinking ill just tack everything up with my flux core wire feeder, and then take it somewhere to have them tig weld it up.

Hey Koaps,

I see your taking classes, how much do you think itd cost to have someone finish up the welds (using tig) on headers for a big v8?  any price difference between mig and tig?  i know theres a time difference.  hmm.. maybe ill just have to hope for the best.  hopefully not TOO expensive, i wanted to redo my vision exhaust too with mandrel bends and have someone weld that up also.  if it ends up being hundreds of dollars i might as well go find a used tig somewhere. :-/

Anyway, thanks for the help everyone.  Ill post pictures of the side panel repair job once i go back and do it again.


Blake

[Koaps]

I'm not sure on prices, though I should learn this. I've seen stuff in my job research for EDD in the $8 to $15 hr rate for various types of welding jobs, but to do a single job i'm not sure, I'm kinding hoping to meet people in class with equipment and start learning with/from them.

My last class will be Tuesday and its going to be demos of MIG/TIG. I can ask the teacher what he thinks about prices, he's a totally funny guy not to mention willing to help out students almost anyway he can, like if I need some 7018 he said why buy a 50 to 100 pound box that needs to be kept perfectly dry, when he'll just give me a handful of them to use when I need it.

I can't wait til next semester when I do MIG and CNC in machining class, but thats all after a long summer of math classes, arg, arg and one more arg cause its a major arg. ?::)