Metalworking Workshop
World’s smallest spot-welding device

The folks at the Italian site Modellismo Hobby Media sent us this email:

During the Spielwarenmesse (German toy fair) the model company ROBBE showed the WELMA 2000: a tool supposed to be the World’s smallest electronic spot-welding device.

This electronic spot-welding device has been specially developed for producing assemblies from steel wire. The point where the wires meet is fixed together using a pair of pliers whose tips take the form of welding contacts; when the start switch is pressed, the joint is firmly welded together.

During the welding process a current of up to 2500 A flows through the contacts for a few thousands of a second.

The WELMA 2000 will sell for 124 Euros (about US$157). No word on availability in the US.

Welma 2000

22 thoughts on “World’s smallest spot-welding device

  1. For $175 to $200 you can buy a wire feed flux core 115VAC welder with 4 settings. You can tack weld thin sheet metal, or run thick heavy beads along 1/4″ steel with ease.

  2. Yes, 2500 Amps is possible, when a capacitor is discharged through a short circuit. It’s just a short peak.
    Discharge time = 1ms
    Internal cap = 100000 uF
    Charge voltage = 25 V

    I = dV/dt * C = 25 / 1m * 100m = 2500 A !

    Of course, a good electrical contact is required, otherwise the current will be limited by the contact resistance.

    So probably it’s just a capacitor in a box, charged by a transformer…

  3. gear head, yeah, those don’t look like 2500 A cables to me either. Wikipedia says “real” spot welders use 4000 – 25000 A, but those have big solid copper electrodes carrying the current to the workpiece.

    Anyway, some more info from the manufacturer’s site: They intend the device to be used with 1mm stainless steel wire to make things like railings for model ships. Here’s a slightly blurry picture of the results

    Jef T, “capacitor in a box, charged by a transformer” sounds like an easy re-make, but the “start switch” would be tricky – how do you switch on a 2500 A load? Are there mechanical switches that can handle this without welding their own contacts together?

  4. Would anyone know if it would be practical to have one of these units with a maximum input power requirement of 115 VAC/10 AMPS. This would be for welding 1/16 inch. maxmimum steel wire.

    1. Oh, we would LOVE to post a review of this on the site. Please do let us know when you get it/review it.

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Gareth Branwyn is a freelance writer and the former Editorial Director of Maker Media. He is the author or editor of over a dozen books on technology, DIY, and geek culture. He is currently a contributor to Boing Boing, Wink Books, and Wink Fun. And he has a new best-of writing collection and “lazy man’s memoir,” called Borg Like Me.

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