Upcycle a Microwave into a Spot Welder

When space is at a premium, you have to choose your tools very strategically. With that in mind, long-time Maker Matthew Borgatti recently completed work on a homemade spot welder, built from a scrapped microwave and a few other parts.

Spot welders, Borgatti explains, are incredibly handy tools, allowing you to tack wire together for quick brazing jobs and permanently weld sheet metal for durable enclosures. While he didn’t come up with the idea himself, his build notes are very detailed, containing links to all of the supplemental materials he bought to create the welder.

The core of the build is a transformer liberated from a microwave found on the street. The transformer was pulled apart and rewound with battery cable, turning the original high voltage low current supply into a low voltage high current supply suitable for welding. The other key part of the build is the timing circuit that controls the cycle times for the weld, built from an Arduino and a rotary potentiometer.

Borgatti even designed and built his own trigger mechanism that uses a cam, and is recessed into the handle of the welder. This means he’ll be able to make multiple welds quickly. The enclosure and trigger mechanism were laser cut, and both off-the-shelf and 3D printed brackets were used to hold it all together, and all the files can be found on Borgatti’s Thingiverse page.

Borgatti’s spot welder is a perfect example of building on the work of others (and giving credit!), and even improving on them. This build is not for the inexperienced, as it involves dangerous aspects such as high current and high temperatures. With that said, for those looking to add a spot welder to their tool arsenal, I highly recommend reading through the project documentation. You may have most of the pieces just hanging around in your shop!