In the thread "Run time before overheating unit?" on this section of the forum, Sundown III posted as a part of his reply - "What I find interesting is that it seems that all manufacturers rate their machines based on amp output, yet the machines only have voltage taps (or voltage adjustment) and wire feed speed (wfs). I guess they expect the user to go to the graphs and figure out how many amps they're really pulling out of the machine." Aye, lads, there's the rub.

Sundown, which graphs do you refer to, where a MM251 is concerned? This is an issue that has just aggravated the snot out of me. Page 31 of the MM251 O&M Manual would seem to indicate that amperage is solely a function of wfs. Various values are assigned, with no indication of where those values derive from, for inches per amp for a specific wire size. That is, .023 wire = 3.5" per amp. .030 wire = 2" per amp. .035 wire = 1.6" per amp. So, according to the book, if 125 amps are required then 1.6 X 125 A = 200 ipm (wfs) for .035 wire. Using that equation, Amps could be derived from any give wfs.

According to this same page in the O&M, voltage only controls the height and width of the bead. Forty years of stick welding before I sat down with a mig welder I worked in a world of amps. I cannot get my head wrapped around volts and wfs.

To the questions at hand. Given a mig welder with voltage adjustment, or voltage taps, and adjustable wfs:

1. Is amperage solely a function of wfs (ipm X constant for a given wire diameter)?

2. Where does this constant originate which is to say, how does one determine xx in per ampere for .045 wire?

3. If amperage is solely a function of wfs, then where and how does voltage come into the mix?

Before I go to my just reward shoveling coal I would really like to finally, completely, understand the function of voltage, and wfs, and the calculation of amps on my mig. I have searched long and hard on the net, but have failed to find the answer. If any of you can educate me, or point me in the direction where I can find it in the literature, I would appreciate it.

Sundown has a very valid point here. You buy a welder and find that you have a duty cycle of 40% at 250 amps. Then crank the machine up and weld at 18.0 volts and 280 ipm wfs. Eh? Ello? Whot? Does that equate to 175 Amps? If so, that seems really hot in my little pea stick welder brain for welding on 3/16" steel.

Sundown, which graphs do you refer to, where a MM251 is concerned? This is an issue that has just aggravated the snot out of me. Page 31 of the MM251 O&M Manual would seem to indicate that amperage is solely a function of wfs. Various values are assigned, with no indication of where those values derive from, for inches per amp for a specific wire size. That is, .023 wire = 3.5" per amp. .030 wire = 2" per amp. .035 wire = 1.6" per amp. So, according to the book, if 125 amps are required then 1.6 X 125 A = 200 ipm (wfs) for .035 wire. Using that equation, Amps could be derived from any give wfs.

According to this same page in the O&M, voltage only controls the height and width of the bead. Forty years of stick welding before I sat down with a mig welder I worked in a world of amps. I cannot get my head wrapped around volts and wfs.

To the questions at hand. Given a mig welder with voltage adjustment, or voltage taps, and adjustable wfs:

1. Is amperage solely a function of wfs (ipm X constant for a given wire diameter)?

2. Where does this constant originate which is to say, how does one determine xx in per ampere for .045 wire?

3. If amperage is solely a function of wfs, then where and how does voltage come into the mix?

Before I go to my just reward shoveling coal I would really like to finally, completely, understand the function of voltage, and wfs, and the calculation of amps on my mig. I have searched long and hard on the net, but have failed to find the answer. If any of you can educate me, or point me in the direction where I can find it in the literature, I would appreciate it.

Sundown has a very valid point here. You buy a welder and find that you have a duty cycle of 40% at 250 amps. Then crank the machine up and weld at 18.0 volts and 280 ipm wfs. Eh? Ello? Whot? Does that equate to 175 Amps? If so, that seems really hot in my little pea stick welder brain for welding on 3/16" steel.

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