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  • welder question

    I have a mig welder sip B and Q cheapy does me great as i use it for steel etc I want to buy one which does stainless and aluminium do I need an ac dc tig welder and can a three phase welder be used through a static invertor running as rotary convertor with the aid of a first thru motor which makes it rotary as I believe I have such a system useable it is 7.5 hp Alistair
    Please excuse my typing as I have a form of parkinsons disease

  • #2
    You need AC for aluminium if it's TIG, but not for MIG. Running Al with a cheapy MIG might be problematic with the feeding, everything has to be just right for Al wire if it's being pushed down the torch.
    Stainless is straightforward with MIG.

    Tim

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    • #3
      I also have a cheapy MIG welder but it is configured to use shielding gas. I installed a spool gun on it for welding aluminum and it works fine.

      http://metalworkingathome.com/?p=374

      This can be made to work with variations on a number of MIG welders with varying degrees of difficulty.

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      • #4
        If you want to do stainless & aluminum you need an AC/DC TIG machine. Provided the RPC is big enough one can run a three phase welder. To estimate the minimum HP rating of the RPC, take the max current draw of the welder and divide it by 2.8. You can also run a three phase welder off of a large enough three phase inverter (like a Phase Perfect). Consult the maker for sizing. You can not run a three phase transformer or resistive load off a static converter. Doing so will probably destroy the converter.

        I don't anything about the unit you have and can't find anything on the web, so I don't know if it is a static converter or a true three phase inverter.

        You can weld MIG aluminum with spool gun and shielding gas and you can MIG stainless with the right wire. But TIG is a far superior process for those, steel, and other things. You can even braze with TIG. MIG is fast, easy, and the machines are inexpensive, but it won't do as many things or do them as well as TIG. If I only had one welder it would be TIG. I pretty much think of my MIG as a hot glue gun for steel when I want quick welding. The TIG gets used for everything else.
        Last edited by jlevie; 11-30-2013, 03:30 PM.

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        • #5
          + 1 for a AC TIG welder

          The local shop (plug for Stump Welding) told me," Welding AL with a MIG is like trying to fornicating with a limp noodle." yes that was a quote. I just wish I would have listen then and gone with a TIG.

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          • #6
            Transformer based tig welders all single phase since the output is single phase. About the only exception is the Miller Aerowave, it is a hybrid transformer/inverter. It uses a big transformer in the bottom that is single or three phase and then rectifies it and has an inverter stage to get it back to AC. Full Inverter TIG machines can be either single or three phase input.

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            • #7
              Originally posted by outlawspeeder View Post
              + 1 for a AC TIG welder

              The local shop (plug for Stump Welding) told me," Welding AL with a MIG is like trying to fornicating with a limp noodle." yes that was a quote. I just wish I would have listen then and gone with a TIG.
              Then he either does not know what he is doing or does not have the right tools.

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              • #8
                Originally posted by macona View Post
                Transformer based tig welders all single phase since the output is single phase. About the only exception is the Miller Aerowave, it is a hybrid transformer/inverter. It uses a big transformer in the bottom that is single or three phase and then rectifies it and has an inverter stage to get it back to AC. Full Inverter TIG machines can be either single or three phase input.
                I don't think that is correct, having used older industrial quality (big) transformer machines that were three phase. AFAIK, they did not have an inverter for AC operation. Having said that, more modern machines that have AC balance control would have inverters for AC.

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                • #9
                  Originally posted by macona View Post
                  Then he either does not know what he is doing or does not have the right tools.
                  Actually you and the shop are both right. The right MIG, spool gun, and wire tuned for a particular production process works very well. Likewise for stainless. But in a home shop, using a cheaper MIG machine, and dealing with a variety (possibly unknown) of alloys you aren't going to get as good of results as with TIG.

                  The fundamental difference between TIG (and torch welding) and MIG/stick is that the former allows for independent control of the weld puddle and penetration versus filler addition.

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                  • #10
                    TIG and MIG have two different purposes and produce different cosmetic results. Sometimes the differences drive the choice. Nobody I know is going to TIG a trailer or jumbo BBQ together, for example, and nobody is going to MIG sanitary equipment. When you have to lay down a lot of welds in a hurry then stick and MIG are the choice, other requirements permitting.

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                    • #11
                      I think MIG or TIG for aluminum will depend on what you are looking to accomplish. What is the material range in aluminum you are looking to weld?

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                      • #12
                        Keep in mind that you'll need three different gases:

                        argon/CO2 for mig with steel

                        pure argon for TIG with aluminum, steel, or stainless steel, and for MIG with aluminum

                        tri-gas for MIG with stainless steel
                        Any products mentioned in my posts have been endorsed by their manufacturer.

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                        • #13
                          Many big dc machines were balanced 3 phase with (at first) selenium rectifiers and many of the ac/dc machines strictly speaking were two phase, with the third phase unconnected to the main transformer. Not surprisingly, the latter were unpopular with the electricity suppliers.
                          If the OP has one of these ac/dc machines it should mate very well with a phase converter provided the correct pairs are connected, of course. If the unused phase powers services like fans, solenoids and hf, he'll need to make seperate arrangements for it. (I think).
                          I can't comment on running an inverter machine with a converter but "it don't feel right somehow".

                          Ps pure argon is fine for stainless, aluminium and steel. Other than helium, it was once all that was available.
                          Last edited by Jono; 11-30-2013, 07:33 PM.

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                          • #14
                            Originally posted by jlevie View Post
                            I don't think that is correct, having used older industrial quality (big) transformer machines that were three phase. AFAIK, they did not have an inverter for AC operation. Having said that, more modern machines that have AC balance control would have inverters for AC.
                            No, it is. FWIW, I was a Miller certified tech up until last year and used to work on welding machines for a living. Even the most massive TIG machines with AC output were all single phase.

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                            • #15
                              Originally posted by Jono View Post
                              Many big dc machines were balanced 3 phase with (at first) selenium rectifiers and many of the ac/dc machines strictly speaking were two phase, with the third phase unconnected to the main transformer. Not surprisingly, the latter were unpopular with the electricity suppliers.
                              If the OP has one of these ac/dc machines it should mate very well with a phase converter provided the correct pairs are connected, of course. If the unused phase powers services like fans, solenoids and hf, he'll need to make seperate arrangements for it. (I think).

                              I can't comment on running an inverter machine with a converter but "it don't feel right somehow".

                              Ps pure argon is fine for stainless, aluminium and steel. Other than helium, it was once all that was available.
                              Not two phase, two phase only ever existed in a very small part of the country around the new hark area. It is a misconception that two phases out of three are "two phase", two out of three is single phase.

                              Most inverters will run off of single phase without any problem, some like PowCons do require de-rating of they full load output when run of of single phase, these were usually the 300 and 400 amp machines.

                              Helium is still used when you need greater penetration.

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