Resistance welding stainless--What Equipment?

greenspun.com : LUSENET : Resistance Welding : One Thread

Equipment recommendation for appliance finish welding of thin gage 430 type stainless. Prefer rocker arm type welder, trip open, 30" to 36" arms.

-- Bill Cole (bcole@rangaire.com), June 04, 1999

Answers

In spot welding most appliances, the show surface is usually very important. You don't want to spend a lot of time and money on a metal finishing operation after the welding job is completed.

As you may know, welding thin gage stainless steel is easy with a resistance spot welder. Stainless is the easiest alloy to spot weld because it is so electrically resistant to the flow of weld current. Thus, your choice of a 30 KVA is probably OK, even though you want fairly long arms. You might want to consider a 50 KVA machine, since they are not much more money than a 30 KVA. Also, be sure that the machine can develop adequate weld force with the long arms installed.(Stainless steel requires more weld force than regular mild steel.)

Many used rocker arms were originally designed for short (18-24") arms, which eventually somehow got exchanged for longer arms with no thought to the fact that the air cylinder located back in the body of the machine is working on the "wrong end" of a fulcram. Thus, the avialable weld force at the tips is reduced and may become inadequate to produce a high quality "Class A" spot weld.

For optimum weld appearance, the best machine for this job would be a deep throat vertical action Press Type Spot Welder, rather than a Rocker Arm. This will avoid the electrode "skidding" that is almost always a result of using a Rocker Arm, especially one with a long throat depth. Skidding is due to the upper tip contacting the metal and applying weld force with an an "arcing" motion, rather than exactly vertical.

This can be overcome with carefull alignment of the arms and by keeping the tips properly dressed. Also, sometimes you can put the show surface against the fixed (bottom) electrode, which would need to have a broad flat-faced or swivel type electrode installed to help prevent marking.

If you already have 30 KVA Rocker Arms doing this job to your satisfaction, then I'm certainly not going to tell you that you must go to a vertical action press type welder, butit would make getting the show surface you want much easier. Please le me know what you think.

-- Tom Snow (welders@tjsnow.com), June 07, 1999.


Moderation questions? read the FAQ