I have had a couple of questions and received great help in adapting a capacitor-discharge spot welder design that was originally referenced by Pommie (See: https://www.electro-tech-online.com/threads/why-the-dip.35601/ ; and https://www.electro-tech-online.com/threads/zener-reference-voltage.35232/ ).
I appreciate it when contributors post follow-up , but noticed the titles for those other threads did not mention spot welder. So this thread is iniated to give follow-up and includes spot welder for subsequent searches.
The design basically follows the idea of Phil Pemberton (https://www.philpem.me.uk/elec/welder) and was modified to include a debouncer for the foot switch and a Variac rather than adjustable regulator for the DC power. I wanted more current to charge the capacitors. I also used audio stiffening caps of 1.6F and 0.5F rather than a bank of computer caps. The 0.5F (Scosche brand) seems to give slightly better welds than the larger Pyramid brand, but that result is preliminary.
So, here are the results. The overall photo shows the prototype setup with the electrodes, capacitor, and debounce/triggering circuit visible. The two weld photos show a razor blade with a strip from a battery welded to it. The other shows the reverse side after the weld had been pulled apart and is intended to show the good penetration. Welding strips has been a problem, as it seems easier to blow holes in the material than to get a good weld. I will probably dull the tips to my electrodes to see if that helps. I used reclaimed battery tabs as the price for nickel sheet (0.004) has skyrocketed.
The next experiments and modifications will include using an IGBT to perhaps shape the discharge time, maybe a short blast followed by a longer one (using two capacitors) or using a cheap 90A tig welding supply ( about $100 at Harbor Freight).
Any comments or suggestions will be welcome.
John
I appreciate it when contributors post follow-up , but noticed the titles for those other threads did not mention spot welder. So this thread is iniated to give follow-up and includes spot welder for subsequent searches.
The design basically follows the idea of Phil Pemberton (https://www.philpem.me.uk/elec/welder) and was modified to include a debouncer for the foot switch and a Variac rather than adjustable regulator for the DC power. I wanted more current to charge the capacitors. I also used audio stiffening caps of 1.6F and 0.5F rather than a bank of computer caps. The 0.5F (Scosche brand) seems to give slightly better welds than the larger Pyramid brand, but that result is preliminary.
So, here are the results. The overall photo shows the prototype setup with the electrodes, capacitor, and debounce/triggering circuit visible. The two weld photos show a razor blade with a strip from a battery welded to it. The other shows the reverse side after the weld had been pulled apart and is intended to show the good penetration. Welding strips has been a problem, as it seems easier to blow holes in the material than to get a good weld. I will probably dull the tips to my electrodes to see if that helps. I used reclaimed battery tabs as the price for nickel sheet (0.004) has skyrocketed.
The next experiments and modifications will include using an IGBT to perhaps shape the discharge time, maybe a short blast followed by a longer one (using two capacitors) or using a cheap 90A tig welding supply ( about $100 at Harbor Freight).
Any comments or suggestions will be welcome.
John