Spot Welder in Homebuilt Design

Overview

The project illustrates how to build a homemade spot welder which can be used for welding two pieces of metal together by producing a highly defined point of contact weld and using a microwave oven transformer.

Details

The welder in this project operates from a secondary 3VAC as the primary is 120VAC. The electrical shock hazard from the electrode is virtually non-existent since the low voltage secondary makes the welder very safe. There are at least 3 functions that the spot welder’s electrodes present including transferring electrical energy to the material while also holding it together, conducting heat away from the material while in the off cycles.

To build the spot welder, some heavy gauge copper wire is also needed along with other materials. A microwave oven transformer (MOT) contributes a lot in this construction where its secondary winding is removed. Rewinding a MOT with 4AWG is difficult and wrapping a layer of electrical tape in their place would help avoid damaging the insulation on the wire as it is pulled through the core. The welding electrode alignment with the material to work on is verified with the power physically disconnected for safety guidelines.