Welding Machine Calibation

[Lapizo]

I purchased a Fluke-336 Clamp-On Meter and looking to calbirate welding machines. Mainly all 400 amp machines. Looking for some guidance as far as how to test (calibrate) the machines. Anyone have a simple procedure they use?

Thanks in advance!

 

[racookpe1978]

Well, it's a bit different than what you'd expect: See, welding is the "art nd science" of applying molten metal into a joint and making a single strong and reliable weldment.

So the "science" side of the equation says you "must" apply 120 amps with a 3/16 rod at 33 degrees from vertical moving at 1.3 inches every 15 seconds on a 75 degree basemetal that's 3/4 inch thick ... Or whatever.

the "art" says that every experienced welder approaching the same joint will want a slightly different angle, feed rate, rod, speed, and amperage than his predecessor wanted.

One welding engineer told me that what he did in the field was put the ammeter on the wire, run the welder controller up and down and check that the amps change with it. You can get "close" to the theoretical spec with an ammeter, but each guy is going to tweak his (or her) knobs a little bit anyway.

Make sense?

 

[Ron]

racookpe...I agree. Back in my college days and early career I did a lot of welding and the settings were more of a "feel" than a notch on the knobs. It also makes a difference whether you have 208, 220, 230,or 460 volts input voltage and whether your feed amperage is near its limit with other "stuff" running. That's for "stick" (SMAW) welding process. For GMAW the settings are bit more finicky.

 

[racookpe1978]

Now, let's figure the other side of the equation: You've got a bank of 120 automatic welding machines running 18 hours per day on two shifts building 10,000 widgets per shift.

You'd BETTER be sure all of them are at the same amperage and speed and angle and temperature ....

 

[gtaw]

The purpose of "calibrating" the welding machine is to verify the meters are working properly.

You can measure the amperage anywhere in the welding circuit and get a good reading. Check the amperage reading of the clamp-on ammeter and see that the meter on the welding machine is the same or at least within 10% of the calibrated clamp-on meter.

Voltage should be measure near the business end of the welding circuit, i.e., near the torch. I usually connect a short lead to the cable in the handle of the electrode holder, torch, or gun and connect one of the leads of the voltmeter to it and the other lead (of the volt meter) to the work piece. Again, what you are measuring is the voltage reading is the voltage drop across the arc. If the welding cables (leads) are short the difference between the arc voltage and the voltage at the welding machine will be small. However, if the welding cables are long, there will be a discrepancy due to the voltage drop along the length of the cables. Here again, if you are checking the meters on the machine simple place the leads to the cable terminals on the welding machine. The machine's meters should be in close agreement with the multimeter you are using.

Both amperage and voltage will fluctuate while the welder is welding. It is better to use a load cell when checking the welding machine's meters because the load is steady and there is little fluctuation. A simple load cell can be constructed using a plastic 5-gallon bucket full of water and one pound of ordinary table salt dissolved in the water. Take two plates with a 1 ½-inch diameter hole in one end. Place the plates on a wooden dowel or other non-conductive material. Attach the welding leads to the plates, one cable to each plate. One of the cables should be to a make/break switch so you can kill the power when necessary. I usually use a SMAW electrode holder with a large diameter SMAW electrode connected to one short length of lead and a piece of scrap steel connecter to a lead running back to the welding machine.

Place the plates suspended from the wooden dowel into the water (remember, the wood does not go into the water). Separate the plates by 6 to 8 inches. The ends of the plates should reach to within 3 inches of the bottom of the bucket full of salt water. Turn the welder on. At this point the welding circuit is “open”, i.e., the circuit is open because the SMAW electrode is not in contact with the scrap steel. Touch the SMAW electrode against the scrap steel to complete the welding circuit. The water will bubble and gurgle as it produces oxygen and hydrogen gas (remember hydrogen will pop or explode depending on the volume produced). Take your ammeter and voltmeter readings. Disconnect the SMAW electrode from the scrap steel plate to open the circuit. The water will get very hot, so be careful. It is not a good idea to do this in an enclosed area. Remember the hydrogen gas. No one minds a little pop, but anything more than that is going to raise more than a few eyebrows and may even singe a few that are too close!

You can slide the plates closer together to vary the voltage and/or amperage.

Good luck (as I hide behind something solid and protective placed between you and me).



Best regards - Al

 

[Ke1thC]

I've calibrated my welding machines using a ring clamp type meter to satisfy a welding audit. My written procedure was to remove the covers from my welders, blow off with compressed air, and take three readings at 100, 200, and 300 amps. It passed a basic audit.

Technically speaking, the meter device needs to be calibrated, annually for my case, in addition to the welders. The last few years I have my welding supply perform the tests for $85 a machine. It satisfies TACOM audits (Department of Defense) because their ISO certified.

Keith