Plastic welding

[crazyal]

Has anyone got any experience in welding plastic? I have few plastic repairs I would like to make, nothing critical. I've never tried to do it and have no idea what equipment works best.

 

[gengine]

I'll be watching this, I've got some to do as well, but have no idea how.

 

[vwnotrunning]

We have used a plastic welder - hot air gun for PVC pipe and sheets. Typically sch 40 or 80 pipe and 1/4" sheets. The hot air with a compressor blows heated air to soften the plastic and you push the "welding rod" into the joint - it all fuses together. Takes alot of practice to get the temperature just right. Too hot and it scorches the material - still holds but sure looks bad.

 

[Tractor Seabee]

Practice! Practice! Hot air welding is a lot like O/A welding of steel except the plastic state goes to liquid faster. You have to watch the heat and keep the filler rod deep in the puddle and stir it around. With lots of practice you can make a bead similar to O/A. O/A experienced welders catch on faster. I have even done it overhead. You have to use the same plastic in the filler rod as the material welding your on is. On pipe we cut off 1/4" rings, warmed it up and made straight. PE cannot be used on PVC and PVC cannot be used on ABS. At least stay in the same family. The torches are fairly in-expensive. HF has one and it comes with an assortment of filler rods. One is probably as good as another. The thinner the material the harder it is to control the heat.

Ron

 

[2manyrocks]

I messed around with this very briefly enough to figure out I didn't know what I was doing. There are different kinds of plastics. Some can be welded. Some can't.

You might want to figure out what plastic you have before you go spend your money on a welder.

 

[crazyal]

I've read a few websites on the subject but haven't watched any videos yet. One thing I wasn't sure of is how liquidy to get the plastic. I'm assuming that it needs to be soft enough to mix the plastic with the rod but not free flowing where it will just run like water.

I've seen tools that are nothing more than soldering irons, some that are a soldering iron with a fan built in, and some that use compressed air. I wouldn't mind hearing what type people have and their opinions on how well they work.

 

[vwnotrunning]

The ones we have look almost identical to the adds in HF. But our cost alot more. The last one I bought was nearly $300 but included a correctly sized low pressure compressor to maintain the air flow. Don't recall the wattage, but the HF would most likely suffice once you got the air flow right.

 

[yomax4]

Once you match the rod to the material ( google plastic welding rod burn test ) You just need some practice..You do not get the base plastic liquid. You want the rod more fluid than the base. Too hot and it looks bad..Too cold and it wont stick. There are many types of rods available from Seeyle and Steinel. LDPE ,HDPE,ABS,PVC, many others. I like the heatgun type as oppsed to the HF hot air vesion. Both work but they are not as fast as Mig Welders. None will make a repair that is not noticeable. It will be obvious that you fix'd it but at least it's not broken.Take your time and practice..It's fun...

 

[SHORT KID]

I bought one of Harbor Freights plastic welders and it worked for me. The secret is getting the right filler rods. On my Troy Bilt tractor there was several of the dash mounting brackets broken. I welded them 2 years ago and they held up well. If you are doing ABS just mix some ABS shavings and acetone, clean pieces up and put back together. If you don't have acetone you can use your wifes finger nail polish remover. Just like metal welding PRACTICE,PRACTICE, and did I mention PRACTICE???? My plastic welds don't look any better than my metal welds, but they hold!!! :thumbsup:

 

[crazyal]

I have some atv parts I can play with to try and fix. I did read a website that talked about doing the burn test as well as using the number in the triangle. I haven't looked to see if there's a recycling code on them, think that would be easier than the burn test to identify the type of plastic.

 

[MMagis]

I haven't looked to see if there's a recycling code on them, think that would be easier than the burn test to identify the type of plastic.

You're right, any piece SHOULD have a recycle code on it, though it may be tough to find. The burn test is far from perfect, even with a lot of experience. As a general rule, a sonic elder will do a much better job than an extrusion or hot air welder, but it's not usually something available for DIY.

 

[Qapla]

I can never get the plastic rod to arc ....

In all seriousness, the only plastic welding I have done was heat welding of floor material when I used to install flooring. In some "clean installs" they require heat welded seams for sanitation (I ran into this in some labs and operating rooms)

They make a special tool for "gouging" the material to be seamed that makes the "groove" in the flooring the same shape as the welding material. In these installations, keeping the hot air gun and the filler material in the correct position and moving at the right speed is crucial. With a little practice, it is not all that hard.

 

[Ozykioti]

Has anyone got any experience in welding plastic? I have few plastic repairs I would like to make, nothing critical. I've never tried to do it and have no idea what equipment works best.

Hey cazyal, I weld plastic for a living so I can try and help as long as you don't live in my area !
The other posts are correct with matching the filler rod to the parent material, must be identical. If you don't have the rod sometimes you can "steal" a bit from an inconspicuous place from the part to be repaired, or a spare part from a donor. Preferably an identical part that is beyond repair or previously replaced with a new one. You need to cut it into strips usually as wide as it is thick, 3mm thick=3mm wide strip.
You mentioned atv guards. Is this what you need to repair? They are usually L.D.P.E, H.D.P.E or P.P, and none of these will stick to each other. You must have the right one.
You need a hot air welder. There are a couple if options. If you want the best chance to succeed you need a purpose built welder. Results can be had with a hot air paint stripping gun ( hair dryer on steroids ) and some are sold with a small nozzle designed for plastic welding. Also come with basic instructions on the process. So it depends on budget and quality of weld needed as to the welder you choose. Hope this helps.

 

[muddstopper]

I guess how much work you need to do will be the deciding factor as to how much to spend for a plastic welder. For my limited use, I just use a cheap welbilt electric soldering iron. One of the pencil type you just plug in and let heat up. My first experience trying the plastic weld thingy was with the plastic fuel tank on my New Holland tractor. I had ran over a piece of reedbar drove into the ground and it punchered a 1/2in dia hole in the corner of the tank. I had already purchased one replacement tank for around $400 and didnt like the thoughts of haveing to pay that much again for another new tank. I made a trip to the local salvage yard and cut a peice of plastic out of a old car fuel tank to use as a filler. I then tried using a paint stripper heat gun to weld the filler to my tank, but either I couldnt get it hot enough, or I was using the wrong technique. Anyways, I had a small electric soldering iron and decided to try it. I seemed to be working, but I had problems getting enough of the area hot enough. I made a trip to Ace Hardware and bought a bigger soldering iron, more wattage, bigger tip, $14 I think. Anyways, this seemded to work perfect. I took my filler piece and stuck it in the hole and started running the soldering tip and filler together around the outside diameter of the hole and just kept going around until the hole was filled. This sealed the tank, no leaks and lasted for a couple of years until I sold the tractor. I have used the same system to weld up some frozen and busted watering cans in my chicken pens, I just used zip ties for filler material for the trays and plastic milk jugs for the bottles. I also welded up cracks in the plastic dash material of the tractor, you can sand the weld then paint the area and not even be able to tell it has been repaired. For welding cracks, I first run the hot tip edgeways along the crack and put a Vee groove almost all the way thru the material. I then take my filler and use the flat side of the tip to melt/weld the filler into the crack, moving the hot tip in a circular pattern to make sure I get a good bond between the filler and the piece being welded. Works for me.

Go on youtube and search for plastic welding, there are tons of videos showing how its done. That is where I first saw it done and what made me decide that it was something I could do without spending a fortune on equipment or need a ton of training to get-er-done

 

[yomax4]

I have an actual plastic welder variable temp heat gun with attachments for different types of welding. After I do a weld, I do the same thing you mentioned. I take a pointed tip butane solder iron and smooth everything out. Works very well. That should be part of the kit.