Capacitive Discharge Spot Welder tips

[boxer4]

Anyone designed/built one of these?

Just wondering about the metallurgy issues and how current/voltage affects them.

I'm having one heck of a time trying to locate large capacity low ESR capacitors. Will a higher voltage and lower capacity be a replacement for high capacitance, low voltage? (by E=0.5C*V*V) Will I just kill the caps or get uncontrollable sputtering if I do that?

What kind of electrodes are good? Will copper spike electrodes be sufficient or will it 'stick' to the work area? Where would one get the tin strips to weld on batteries?

 

[ericgibbs]

Anyone designed/built one of these?

Just wondering about the metallurgy issues and how current/voltage affects them.

I'm having one heck of a time trying to locate large capacity low ESR capacitors. Will a higher voltage and lower capacity be a replacement for high capacitance, low voltage? (by E=0.5C*V*V) Will I just kill the caps or get uncontrollable sputtering if I do that?

What kind of electrodes are good? Will copper spike electrodes be sufficient or will it 'stick' to the work area? Where would one get the tin strips to weld on batteries?

hi,
Lotsa links on Google.

https://groups.google.com/group/sci...hread/bfafcf99f4038e8e/69bbe54035b19826?hl=en

https://www.electro-tech-online.com/custompdfs/2007/08/Resistance.pdf

Eric

 

[waxman]

Some good info on the Unitek website. They wrote the book on small spot welding. Copper is a very common electrode material, but you must consider all the metallurgy to match electrodes with parts to be welded.
For example, those tabs on batteries are typically nickle.

 

[technogeek]

I built a spot welder from a microwave transformer by rewinding the secondary with #8(?) gauge wire.

Cost was about $2, because the microwave was free! It was broken, but the transformer never breaks. Usually it's the diode or cap.

Might not be the answer to your specific questions, but it's probably a simpler design.

 

[boxer4]

Interesting, and thanks for the links - I was researching this a few months back and never saw those! I also wonder why I wrote tin, I was about to do something illegal and flatten nickels for a source of nickel strips - a 5 cent piece would make a lot of strips (and cheap, to boot) just kidding!

I wanted to go to a Cap Discharge device because of the short duration of the pulses and it's hard to fry something with limited energy. However, then the exploding caps issue is the new issue I'd have to deal with.

I have two 51mF 40V electrolytic low ESR caps someone was tossing at a hamfest. Hoping those will be sufficient, getting my parents to mail me my 0.3F 6V cap along with a whole mess of other large canister electrolytics (and I'm not sure which ones are low ESR or not) would be tough since they don't like mailing...