Welding Machine Calibration

[glakics]

I know that a load is used for calibrating welding machines, although a DC amp probe will work for "Verification". Can you tell me if anyone has a standard procedure/process for verifying welding machine accuracy? +/- about 5%.

I can interpolated guage readings against actual readings and graph a curve of accuracy. But is this a reccomended practice by manufacturers?

Thanks
Greg

[dseman]

There have been some people in the past posts who have wanted to meaure voltage and amperage at different settings. I believe this was done because they wanted to establish a table of general parameter settings that they could use across several machines--baby migs, medium migs, lincoln migs, hobart migs, and miller migs. These were basic transformer machines with no voltage regulation, and whose wirespeed dial indicator didn't display actual wfs, but rather a percentage. This can help, but with differences of slope and impedance from 1 machine to another, the best that can be hoped for (imo) is an approx. of where to start. So if you only have 1 machine, I don't really see any need to verify what the welding mfgr. has stated. You set the machine based on what the metal and joint requires. If you want to re-label your wirespeed control to actually indicate ipm, then this may be helpful when comparing data from electrode mfgrs--since they usually post amps/volts/wirespeed ipm guidelines for all of their different filler wires. Most pros would say they set the machine by the sound, weld pool size, and final appearance of the weld bead. If they are using an unknown filler they may refer to the electrode mfgr. tables as a starting point.

Are you a large user of multiple machines and believe you are not getting rated output? In other words, what is your motivation for wanting to correlate your measurements with what the mfgr. specifies?

-dseman

[Guest]

Fascinating question, Greg...it piques the interest. Welcome to the forum..the gurus at Hobart will be able to tell exactly what you are looking for. They are super folks and really care about those of us who use their equipment.

Your question is somewhat cryptic, in that it raises more questions, like "why" do you need this info. My guess is....(just fantasizing, now)...you have a procedure that you want to run in a robotic situation, and you need calibrated machines. Am I close?

[glakics]

Sorry for the confusion everyone! I will give more detail
I am the Quality Engineer for a Welding/Fab shop (12 welders-mainly GMAW & FCAW process).
I have established our ISO-9000 system which requires the "calibration" of our welding machines. Being a CWI myself, I know that calibration of welding machines is a bunch of crap. You weld by sound, sight, feel etc.. Calibration is really not required. Only the verification that if I put the dial on 17 volts am I truly getting 17 volts at the torch? I can plot a chart of these 2 curves meaning [email protected] machine=17.2v at torch. [email protected]=18.7v @torch. [email protected][email protected] Then I can justify to myself, and the ISO auditor that when I put the dial on 20v it is actually 21v at the torch. The same can apply with CCV & CCA machines. Just look at the DC current instead of the voltage.
Do manufacturers recognize this practice to be "OK"?
Or is there another method for pleasing the ASSO I mean ISO auditors.

Thanks,
Greg
P.S. I establish UL ISO systems, and we really do appreciate what the auditors do for us.

[dseman]

Ah, now it makes sense. ISO-9000. We have to keep our lab equipment calibrated as well. Sorry for the confusion, I thought you were taking another tangeant with your question. I'm sure the Miller boys will know what an acceptable procedure would be.

good luck,
-dseman