The first was a cheap hot-air type. It worked ok but the temp was hard to control.
The seconds was basically a soldering iron with a paddle tip. It worked well but the tip shape was not great.
What looks to work well is what is called a "speed tip". It is a flat tip with a tube welded to the back. That gives you a wide area to heat and the new plastic is fed through the tube.
Some plastics are easier than others. ABS was real easy.
Yes, that heats the plastic and allows you to feed the rods into the softened plastic. With just a heated tip (mine looks like a dental mirror) You cant feed very well.
Note: you need to push the rods fairly hard for it to work right or it just sits on top.
A heat gun with an accurate temp control is needed. My air one was way too hot and was not adjustable.
I have done a bit of plastic welding used to make clean air filters for an animal health company. The torch was made by Lister the same as a floor layer would use for welding vinyl floors. The unit had a temp regulator and you could also adjust the flow of air as a means of fine adjustment. Came with various tips for round and triangular filler rod does not take much to master the skill. Handy for welding farings and car bumpers but found the weld to be a little britle.
Have welded bike farings before the filter units were 6mm on the outer flange and the pipe was around 3mm thick, if it starts to turn brown on the outer enge adjust the heat down I used to look for a nice sheen on the outer edge remember and let the plastic start to melt before applying the filler rod p.s. keep the rod out of the nozzle untill the plastic has started to melt or you will end up with a limp rod!!!!
Just had a look at the fleabay unit looks like a Lister copy but the vent at the rear where the switch is had a slide so you could adjust the air flow for a finer adjustment of temp.
i use the leister gus at work. just waiting for 2 more guns to come actually. we do alot of landfill projects as well as making boats etc. look in my albums
we have a couple of different welders, ones we call tackers http://www.welwyntoolgroup.com/leister-welding-pen-s.aspx where you manually feed welding rod in through a hole above the air hole . or use no rod and use the hot air and a pointed tip.
or these ones http://www.welwyntoolgroup.com/leister-fusion3c.aspx not good for tight spaces but there very fast compared to our older ones. pain in the **** to set the temperature as the red dial gets knocked easily which is why we moved them round to the opposite side. plus the hurt when you touch the barrel. it burns.
atb scott