Thermal sensor clamp for Clarke 150A MIG welder

thingiverse

These 2 brackets are used to mount standard NC thermal safety switches to the transformer and inductor of a Clarke 150A transformer-type MIG welder. They need to be printed in a temperature resistant polymer and I used colorfabb's HT filament. I've used 65C thermal switches which might be a little over-sensitive, if I was fitting it again I'd probably use 75C units. It's a good idea to use silicone thermal contact pads otherwise the switches will make only very poor contact with the windings. The brackets are anchored back to the transformer and inductor using M5 threaded rods and nyloc nuts. Electrically I used this by putting both switches in series with the coil of the main contactor, there's probably a more elegant solution but the [rLab](https://wiki.rlab.org.uk/wiki/Main_Page) MIG welder has been hacked around quite a lot and this was the best option I could find. I've also placed a 240V neon on the front panel wired across the switches so that if the welder attempts to operate but it inhibited by the thermal safety the warning light will come on.