Toying with the idea of getting a plastic welder.

Inexpensive stuff is basically a high wattage electric soldering iron that you use to melt and shape plastic. Crude, but...well...crude.

High end stuff is hot air with various tips to concentrate the air flow. Unfortunately, $400-$500 is out of my budget.

Did see one mid-price hot air system that tempts me.

What does the brain trust recommend?

what are you going to weld?

ATV plastic...fenders, etc. would be the main thing.

I know there are a raft of different plastics, each with it's own characteristics. The ATV stuff tends to be a nylon-like flexible plastic, but don't know the exact composition.

You mean something like this?

You might look at the Eastwood website for this including Hot Staples .

I have this for a soldering iron
Hot air soldering station
It is rumored that it has melted a few plastic items back together that were inadvertently broken while I was NOT playing with them.....
They make a bunch of models - the hot-air only one is ~$100. It's REALLY handy to have iron+air when you need to pull relays off a PCB because you designed the footprint upside down & need to put them on the opposite side of the fucking board.

An extra set of hands & a cheap heat gun to pre-heat the area can help with a large section. I doubt you'll get humpty dumpty back together, but it can make cracks less noticeable.

Does it work on Kydex?

As an auto hobbyist I’ve been welding plastic for years. Anything that will melt the material works well enough. I’ve found material that lets you weld everything from white plastic (like milk jugs) to hard plastic like the composite butt plates on a shot gun. The front and rear bumper fascias on cars require imbedding stainless steel screens for strength. Try it. Easy to learn. And very handy. You have to investigate what types of materials you need to weld, and what material is compatible.

I'd really like to get someone to weld the crack on the Shield frame in my safe...I think it could be done.

I worked at a place that had an ultrasonic welder. They didn't use it much but I thought the concept was cool.