Spot welding voltage & current

Welding Techniques, Theory, Machines and Questions.

Moderators: Harold_V, Scott

Post Reply
TomB
Posts: 441
Joined: Mon Jan 14, 2008 7:49 pm
Location: Southern VT

Spot welding voltage & current

Post by TomB » Sun Feb 17, 2019 1:38 pm

I'm wondering if it reasonable to build a spot welder for manufacturing a welded wire product. It would be welding approximately 3/16 wire to 1/8 wire in a repetitive pattern. If the idea works I would need to do quite a bit of this type welding but always in the same pattern. I have not looked into specialized welders as I can't imagine how they could reach the spots to weld but I guess a general welder with custom built electrodes could work. That said are the general welders different from the boxes that do my Tig and Mig welding?

Tom

John Hasler
Posts: 1266
Joined: Tue Dec 06, 2016 4:05 pm
Location: Elmwood, Wisconsin

Re: Spot welding voltage & current

Post by John Hasler » Sun Feb 17, 2019 2:15 pm

Spot welders are quite different from arc welders. They rely on resistance heating in the parts being welded rather than on arc heating. This requires that you firmly clamp low-resistance contacts directly at the spot where you want the weld. The open circuit voltages are quite low (on the order of 3 volts) and the currents quite high. Water cooled electrodes are used in industrial spot welders but that's only necessary if you are running production and can't afford to let them cool or you are doing large welds with extremely high current. You shouldn't need it.

There is lots of stuff out there on the Web about DIY spot welders. Most use modified microwave oven transformers but you could also modify an arc welder transformer.

You probably could spot weld with a stick welder (actually, we've all done it) if you fabricated some electrodes and added a contactor so that you could switch it on and off quickly

TomB
Posts: 441
Joined: Mon Jan 14, 2008 7:49 pm
Location: Southern VT

Re: Spot welding voltage & current

Post by TomB » Mon Feb 18, 2019 11:18 am

Thank you John. That was what I needed to know.

Post Reply