I have made my own Capacitive Discharge welder for the purpose of welding nickel tabs to C-size NiCd batteries. The welder consists of a capacitor bank (500,000 uF) discharging through an SCR. I can adjust the charging voltage from 0 to 12V. The electrodes are pressed against the parts to be welded from the top, by individual air cylinders where the pressure may be precisely adjusted up to 30 pounds. The electrodes are 1/8 dia. class II from T.J.Snow, trimmed down to .080" at the tip. The welder produces very strong welds reliably and repeatable. The problem: The electrode "sticks" to the work piece. I have tried different electrodes, including pure copper, different charging voltages and electrode pressures, but the problem persists. Are there special electrodes for this purpose? Is the problem with the welder? Your help will be greatly appreciated. Thank you.

-- Daniel Bernesi (danber@telicom.ca), August 04, 2002

Answers

Assuming the Ni tabs are .005" or thinner, try doming the electrodes. If your tabs are greater than .005", you must either use a "slotted" tab or place a projection on the tab. Use between 6-8 lbs of force (measure with force gauge). Set you CD welder between 40-60 Watt Seconds of energy. Try a "dual pulse" if your welder is capable. Hope this helps. Kurt Tolliver Unitek Miyachi Corp.

-- Kurt Tolliver (kurt@unitekmiyachi.com), August 04, 2002.