I'm fishing for any experience and suggestions for ABS, specifically motorcycle fairings since they are usually thin, curved planes. In the mean time I figured I'd share some of my experience.
Doing TIG and 3d Printing I figured it'd be a breeze but there is still a learning curve here. The two videos below are about the best I found to give advice on where to start. Like TIG you're using a filler rod but they make a speed tip that lets you feed evenly, consistently, and much faster than by hand. Unfortunately the HF models do not come with this tip but it looks like some other models so likely it's a knock of with sourceable accessories. Like TIG you also have a puddle and your melted edges to watch and like a good weld, smooth and consistent is usually perfect. The overall process is much like the lay wire technique except you're stabbing straight down. With thin stuff you do need backing to prevent burn through but a gloved hand seems to work pretty well. Depending on what you're doing you will find needs to push filler at more of an angle but like TIG, straight up and down is best.
That's where the similarities end though, oh yeah except clean, Clean, CLEAN! The key difference (besides the obvious) between plastic and TIG welding is your plastic heater angle vs TIG torch angle and travel. Basically you're working in reverse so your heater is facing opposite of the direction of travel so it can heat the part about 20% of the time and the filler about 80% of the time with a fanning motion to and from the part and filler. You're also swapping your TIG torch angle for your plastic filler angle, and your plastic heater angle with your metal filler rod angle so you're keeping your plastic heater about like 45-20 degrees while the filler sits at at 90 degree angle to usually at most 60.
After all this TIG'in, let me tell you this will mess you up because it feels like you're TIG'in till you start!
When cleaning plastic it's best to scrape the material off rather than sand it since the dust will complicate the weld and plastic is notorious for trapping that stuff since it pits easily. Similar to metal but much more pronounced. Don't grind it either it will melt quickly then you're repairing more
So an exacto, razor blade, or some fancy scraper/cutting/chisel tools are best. MEK, Methyl Ethyl Ketone 9 is the best stuff you can post/pre clean plastic with but variations of alcohol usually work well too. Soap is just fine so long as you rinse it. One thing you don't ever do with ABS is use Acetone! It is acid to ABS and will liquefy it with enough Acetone. Now you can use acetone for light welding, joining, since it does evaporate quickly so you could use it to help with basic tack welds but it is gooey, you must let it dry, and it will destroy your liver if you come in contact with just your skin too much. Yep it's what used in that stuff ladies use to clean nail polish off with their bare hands too.... Acetone is good for smoothing down parts and if you're smart/safe you can even steam an ABS part with Acetone to give them a smooth, glossy finish. Be careful though since you can burn or kill yourself and seriously damage some property.
One other neat thing about plastic welding that does differ from TIG is tacking. There's curvy rocking chair base lookin tip for this. Unlike TIG, you get to run a full length for a tack if you want to which is performing an autogenous weld. Like TIG though, if you're going to do a filler weld, you should tack first but tacks are generally more important to plastic then TIG.
So how do you use that weird tacking tip? You hold the plastic heater at around 60-80 degrees with the point of the tip touching into the seem you're going to weld lightly then you drag the plastic heater in the opposite direction the tip points at along your seem. It's really fun when you got a spidery crack. The key thing to remember, do not put the opening port where the air first comes out against the part so the tip is pointing up otherwise you're in for a mess especially with a tack since usually you're working at your thinnest point or a gap so you will melt through.
One of the best parts about plastic welding is you don't really need a lot if any safety equipment. Usually safety glasses are recommended and gloves certainly make things easier and you can handle. Gloves allow you to also mold your parts of hold them in place and with most thermoplastics like ABS, it's pretty easy with a pair of decent mechanics/welding gloves. You can also smooth out plastic to an extent by heating it with your plastic welder or a heat gun too so less need to grind/sand
Even if you don't do 3d printing, the filament options are quite extensive and with a lil heat gun and a bit of patience you can straighten the rolled filament into rods that would mimic TIG welding. If you do 3d printing then now you've got another use (if you're not recycling) for all those failed parts. You should have misprints, random shapes, mesh grids, and all sorts of interesting things to use to repair things with. You can even print replacement pieces to weld into your broken part. You could even build a plastic encasement and then plastic weld it around a metal project of sorts. The imagine is the limit especially if you can weld metals and plastics
https://www.youtube.com/watch?v=GVr8wHIcgCo
https://www.youtube.com/watch?v=HvV9a3lEe2g
