World's smallest spot-welding device

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By Gareth Branwyn
Posted 2009/02/19 @ 2:17 pm
Category Tools, Workshop

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.

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10 Responses to World's smallest spot-welding device

Timm Murray on February 19th, 2009 at 8:25 pm said:

Is that a model train transformer hooked up to some needle nose pliers?

Time for a remake?

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gear head on February 19th, 2009 at 8:43 pm said:

I’m sorry, 2500 amps?

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craig on February 19th, 2009 at 9:00 pm said:

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.

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Jef T on February 20th, 2009 at 2:45 am said:

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…

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mikey on February 21st, 2009 at 10:35 am said:

You could make some radical sculptures out of paper clips with it, though.

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i on February 22nd, 2009 at 2:56 am said:

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 http://www.welma2000.de/content/images/0247e2de7ff28f7b037efefd380f475a.jpg

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?

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Tyrone on March 19th, 2009 at 8:51 pm said:

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.

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Jade Harker on September 28th, 2011 at 5:57 am said:

Please share more information on how to use, features and many more.

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aczez on July 24th, 2012 at 2:25 pm said:

Just ordered one directly from Robbe, will write a short review when i receive it.

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- Gareth Branwyn on July 24th, 2012 at 3:05 pm said:
  
  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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