calibrating?

[jadmo]

Can anybody tell me if digital readouts on wire feeders ever need to be calibrated?

[ASKANDY]

Kind of depends on whether you are welding on something that needs certs or has a standard weld procedure that needs to be adhered to.

The meters are normally for reference but they can be calibrated using a meter that had been calibrated to the NIST standards and verified with paperwork.

But if you are asking wether they fall out of cal over time, no they usually don't.

Andy

[Bodybagger]

If you suspect that the wire feed speed as indicated may be off, take a stopwatch and feed it for 6 seconds. cut the wire and measure it. Multiply it by 10 and you have the true wire feed speed in distance per minute.

[cruizer]

These calibrations are mainly for procedual welds or if you happen to be ISO certified. Really they are just a cash cow for my business as they don't mean much.

[diamondback]

digital meters probably cant be calibrated like the analog meters with the knob on the back. Usually it is a board change. There is a range that is acceptable before the meter display is bad.

[cruizer]

There are procedures for calibration of most (not all) equipment, some are via on board diagnostics, others with board potentiometers. though you need a load bank and certified meters to do it. Costs alot to have our meters calibrated to do others' calibrations.

Machines we load to its data plate parameters for inspections, then dial down to compare our equipment with thiers & make changes if required.

If thier guages are within 5% from min to max, we leave it alone.

[hogan]

jadmo,
I don't think it is a matter of calibrating a digital readout. Many codes/standards will require that a digital readout be verified. I am required to do this every 3 months to retain certain endorsements/certification. Currently these requirements are mandated by AISC (bridge certification) and CALTRANS work performed by our shop. In a nutshell, you go by the machine manufactures recommendations. All of our equipment (Hobart,Lincoln, and ESAB) manufactures recommendations are that the machine operate at + or - 10% of what is noted on the display or dial. If your dial read 500imp of wire feed speed, then check to see if it really putting out 450 to 550 imp. Same with amps and volts. hope this is what you were looking for.

[cruizer]

The whole calibration thing except for the operators say on subarcs is quite silly from my point of view. (+-10% on a subarc is a big deal)

The operator knows if his/her machine is operating corectly. I don't know too many operators running a mig who can watch the guages while welding.

If a shop is really intent on following procedures, then they would use a feeder or powersource that can be "locked out". On most tech ESABS for instance, while you can't really lock them out due to master unlock codes, they do have language settings, so I stick them either in Chinese or Porteguese. The operator doesn't have a clue after that, and can't fiddle with it.

Then there is the power issues, say if the building is 208, and the machine can only run 230. There's a problem on the power source as it'll never make the volt/amp nema spec, or say of a large power drinker like a shear or a brake is on the same breaker panel as the welder. XMT's , excluding autolines, will throw a fit, though those can't be calibrated anyways.


Other variables include:
machines tested hot, machines tested cold

Calibrated machines with procedures using various resistance rods, variable resistance wire, type of gas from various companies, length and size of weld cable, torch cable or control cable (as the power source meters are never the same as the feeder guages), gas flow settings, different operators, different stickouts. Type of material being welded, if there is a coating on that material. even down to the humity in the shop plays into it.


Stand alone feeders other than the tech Lincolns with onboard diagnostics can't be truly calibrated, nor tested to a NEMA Data plate configuration..

Thats why I call it a CASH COW, as one would need a perfect world to be trully accurate.

And again thats why we test the machine to a NEMA configuation first, otherwise I can make that machine read what ever I want.

[diamondback]

Calibration comes into play when process controls are documented and verified. Many larger cities such as L.A. or Clark country Nevada are quite strict on what they will allow. Props to the guys who work it everyday. ISO qualification also may contain a calibration portion depending on how the process is built. Their idea is if you say you do it prove it. Just having the number right on the read out isn't enough.

For a machine that can lock parameters take a look at the Axcess family and the pipepro 450 RFC. These have the ability to lock ranges, it's really pretty cool.

Power issues are also addressed by Miller with the Auto Line products. You can plug into almost any outlet 208-600 volts and get the same arc. This is on inverter machines. You can even run an Axcess on single phase 240 as long as your wire diameter is small for current draw.

For the other variables discussed such as humidity, cable length etc. some of those items are not part of the machine and are not part of the calibration. The typical standard addresses the machine and not the welding circuit. Others while having some effect it will be negligible due to product design and testing as well as in service conditions. If you test a machine in place then the humidity will be the same when you hook it back up and run it.

To calibrate a machine you would use a load bank with meters and most of the time go to the welder to test. The machine hooks directly to the load bank and the test is just minutes to run. Not all calibration techniques need to be identical just repeatable.

There are times I think calibration is a good idea and times I don't it depends on the situation.

I would have a hard time assuming the operator knows .......

[cruizer]

Well, there is no set way to actually "calibrate" a welding machine according to ISO standards, pretty much any halfwit with a loadbank can do it. There is no qualifications to pass. Nothing. Only standards to be followed is with the individual manufacturer. Yes I am aware of the Axcess machines. I have integrated them with other machinery using PLC programs.

If there was some sort of standard to follow I'd be game to do it, but there simply isn't.

Generally, I refuse to do an onsite calibration unless it is required from a technical perspective, not supposedly going out and calibrating non calibratable machinery like a bunch of XMT's or SRH units.

[diamondback]

I can agree with you on the standards thing, pretty much whatever you can do repeatably and document. Someone who knows how to do it can charge a lot because it's "calibration". I got raked over cost wise because we had to have it done outsource since we didn't have documentation on how to do it. I bought a load bank and wrote a spec and gave it to a weld tech to take care of.

For the digital meters it was verification only, and if it was out of spec from Millers perspective with the +10% then we pulled it out and sent it to the LWS for a board. Not much else you could do when ISO has to be satisfied.

Sure it's a game, but you also want that ISO cert to satisfy the big dogs.

[cruizer]

What I find in the field is looking at a report that says 50, 100. 150. 200 amps/volts ect and comparing the calibration meters and load bank, is that it doesn't tell you or the inspector how well that machine in question is actually performing.

A failed machine will NEVER reach the machine in questions data plate specification, However, simply testing the visual outputs can trick you into thinking that that machine is performing like it should. Like I mentioned, I can manipulate that visual display into reading anything I want. Without having a standard of calibration via the machine's data plate criteria, a true calibration is absolutely worthless.

I prefer the Lincoln 750 Masterload as you can toggle the loads up and down live, as apposed to shutting the machines output off with the Miller version.

[Shad0w]

Calibration

How often would you recommend calibrating a machine??
What does AWS require?

[cruizer]

Pretty much never, unless its a procedure weld or if your firm is ISO certified.