Nice looking project. The PDF plans do look nice. Note to anyone in the US considering building one, it is designed to run on 220v input. Most of our microwave transformers are 120vac input.

One suggestion I would make in regard to construction. The tips should be more easily replaceable. They are consumable. There are also many times you want a special set of tips. For example when welding crossed wires as shown in the video, grooved tips are nice to help with alignment.