I dismantled an old microwave and used it to build a spot welder.

The housing is made exactly to the microwave transformer I found and may need to be adapted to your transformer.

I took the following from the microwave:
- Transformer
- Stands

I ordered:
- NY-D01 100A Board (https://de.aliexpress.com/item/33040580897.html?spm=a2g0o.order_list.order_list_main.134.773b5c5f8JwvMg&gatewayAdapt=glo2deu)
- matching AC220-9V transformer (https://de.aliexpress.com/item/33040580897.html?spm=a2g0o.order_list.order_list_main.129.773b5c5f8JwvMg&gatewayAdapt=glo2deu)
- Welding machine handle (https://de.aliexpress.com/item/1005001603385952.html?spm=a2g0o.order_list.order_list_main.119.773b5c5f8JwvMg&gatewayAdapt=glo2deu)

From my electronics treasure trove I took:
- Connection for the welding machine handle
- On/Off switch
- Fusible fuse holder
- Cold device connection
- Thick cable

In the shop around the corner:
- long cord from which I knotted the device handle with a paracord

I originally wanted to print the enclosure out of ABS, but at the time I only had PLA in stock and my printer at the time didn't have an enclosure.
Despite PLA, my welding machine is holding up great.