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CO2 generator

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  • #46
    Its a gas man!!!

    Odd this gas bit.

    Seems to be "just use it".

    You will get air in the weld zone if gas is deflected by air currents and drawn in if the gas flow is too high.

    I make sure my MIG welder is set for gas flow pre and post weld.

    Arc length as well as nozzle/shroud protrusion/cover all have an effect on the weld-metal transfer and spatter - open-circuit voltage as well as the size and quality of the leads (earth in particular) and clamp/earthing are also big considerations.

    Unless or until all or most of those are eliminated as problems it would be difficult to be sure that the wire (cored or not) and/or the gas or lack of it was to blame.

    All of my MIG work is on steel and 75/25 (called "Universal" here) works very well.

    As said previously, bottles here in OZ are owned, maintained, filled and rented from the suppliers - Liquid Air, BOC etc.

    I have oxy-acet as well - same basis.

    No MIG as I use Oxy-acet as normal for some metal work and for "as good as TIG" using my "Cobra" (aka "Dillon") torch which uses Oxy-acet at 4psi - great jobs, great tool.

    For plate and sheet cutting (any conductive metal) I use my plasma cutter - only gas is air from the compressor.

    I can see that re-filling from your own manufactured CO/CO2 might be a good "interest" or "academic" exercise, but I can't see the cost justification.

    I don't complain about consumables or running costs as its part of getting the job done and the chances I took when I bought the gear.

    Having it here ready to go as required is not only very convenient but has saved me a good bit of anguish other-wise and while that is intangible to a degree, it has saved having to get it done by others during their business hours at their premises. PITA mostly.

    I do hope that is all works out in the way that those who intend to make their own gas hope it does.


    • #47
      Gas welding also doesn't use an arc that creates far more heat than the neutral flame. Gas filler rod is also chemically nothing like -S6. The alloying elements and deoxidizers are entirely different.

      Your using a 135 explains a lot of it. The arc voltages on that size machine are very limiting for a good metal deposition rate or even effective melting of the base material. If you had faster feed, with higher voltage (which combined, you know means higher wattage) you'd end up with much more porosity and burning of the base metal. The simple fact is you're barely melting what you've got.

      That size machine has it's place and can do a lot of work, but it's a big limitation to getting the material hot enough for good penentration and fusion. I had a MM130xp for a number of years. I wish I wouldnt've sold it, because it was great with .023 wire on thin stuff.


      • #48
        Originally posted by lazlo
        No. It costs trivially more to fill a larger bottle with any gas, and you'll run through those little "burglar bottles" in under an hour. The welding gas suppliers are mostly charging you for the overhead, and not the gas.
        That's what I'd have guessed. My large oxygen bottle goes empty fast so I can't imagine a little bottle like that lasting long. I don't need to weld often but when I do it is usually a repair that looks like crap from using fc wire. That stuff lights up like a fireworks barge.


        • #49

          I think you are underestimating what that welder can do. This is a piece of 1/4" plate welded to heavy wall tubing with flux core. Normally I would use stick for this but I wanted to see if it could do it.

          The weld beads shown previously were done at no more than 1/3 of full power. I mainly use the Miller for light gauge material up to .125 at most.
          Free software for calculating bolt circles and similar: Click Here


          • #50
            A real bottler

            Originally Posted by lazlo
            No. It costs trivially more to fill a larger bottle with any gas, and you'll run through those little "burglar bottles" in under an hour. The welding gas suppliers are mostly charging you for the overhead, and not the gas.

            I agree that on the face of it, those small MIG bottles are a PITA and expensive and all too often have a fixed-rate regulator (of sorts).

            That's probably true for the work you and a lot of the rest of do in your/our shop/s.

            But for some-one up a ladder or in a roof/small space etc. and who has only domestic-type and/or large volt-drop long lead single-phase low amp power supplies - they are great. Some use with, others without gas but the better jobs are with solid (small) spool wire and gas in preference to wire-cored/fluxed spooled wire.

            There are a range of gases and wires - stainless steel included. They are very handy for commercial kitchen work and some medical and laboratory and hospital work etc.

            I've seen them used for welding on cleats to structural frames and connectors for tilt-up slabs etc. (enclosed and out in the weather).

            In the right conditions in the hands of a good operator they are not only very useful but are the only practical and cost-effective way of doing some jobs.

            Mind you though, most of them are considerably better and more expensive than many "consumers" will buy. "Price points" and supply and demand again.

            Its horses for courses.


            • #51
              Flux core, or straight co2 is going to give you the hottest puddle with that machine - I had one. But you've got nothing on a 240v machine, even a little 175A unit. Duty cycle is the next biggest hit you take with that thing (aside from not being able to get good heat into a .250" joint). 20% at full output means a whole bunch of waiting between squirts. You can only pull so much wattage out of a 120v 20A circuit. Once you get into the 240v machines, you get a whole bunch more heat in the puddle.

              Like I said, they're awesome on thin gauge stuff and I wish I hadn't sold mine because my invision 354mp is 50# and needs a feeder, and 240v to be happy. Little boat lift repairs up at the lake would be ideal for that machine, but I needed the money 4 years ago when I upgraded it to a thermal arc 250A rig. That was good to me till I got into a lot of aluminum tig work last year and decided a push-pull aluminum mig rig would be better profit, so I got the invision power source and an XR Control for it with a 30A. Added another feeder for steel and I've been happy ever since.


              • #52

                Nice looking weld Evan.

                Good points Jim.

                Its all about "Duty Cycle", cleanliness, good earthing, good power supply and good cables.

                Duty Cycle is the percentage time of welding in any 10 minute period. At the top of the current range on a small machine, the duty cycle can be as low as 20% - 2 minutes maximum in any 10 minutes.

                Draw too much current or lift the circuit-breaker and you have no power to the cooling fan and the welder could "cook" particularly if you over-do the welding time.

                I don't like the "gun" or its construction on small machines. Many of the drive rollers will "slip" if there is a sharp-ish bend in the lead as there is usually only one roller driving - the other is just a clamp and is an "idler".

                Both of my drive rollers are geared together - one driving the other so I have a two roller drive instead of a single.

                My 230V 240Amp machine has a 100% duty cycle at about 120 amps which is about where I have it set mostly.

                Some will disagree with this, but just as I pick up the gun I "fire" it to get gas into the shroud just as I am about to start. The shroud is now "charged" with gas. I always use a pair of diagonal pliers/cutters to "snip" the ball/"blob" off the end of the wire before I commence so that the wire size is consistent. I pause and "back-run" at the ends to fill the crater and to reduce cracking - makes "re-starts" a lot easier too.

                I wheel my welder out into natural light (sun behind me) for best illumination - streets ahead of any other lighting.

                I always clean my reading glasses (no bi-focals) and inside and outside of the welding hood (auto) lens with an excellent lens cleaner (in an aero-sol can - quite cheap from my welding supplier) which makes seeing so much easier.

                Many welding (especially MIG) problems are blamed on the gas or the machine but may well be caused by the operator - poor vision and/or technique or poor set-up. Its worse at low currents.

                If my welding looks OK and sounds like "cooking/crackling bacon in a pan" its a good guide.

                Oh, if I haven't run the machine for a while or I want to check my set-up and/or technique I sort it out on scrap first and only on my required job when I am reasonable satisfied.

                If using gas make sure that the work area is screened from any breeze/wind that might blow the gas "off-target" during the weld.

                And with all that good gear and advice do I (still??) cock stuff up - damn right!!!


                • #53
                  Evan, you should really try a machine with adjustable inductance. With how much you like to tinker, I think it could provide you hours of entertainment without ever doing anything productive. (meant in kind jest)

                  I'll be welding some steel later this week (if I get my way), and I'll take some pics. I'm certainly no god to welding, but I can stick the stuff together and make it stay.

                  OT, I like the nimbleness of the M10 guns for sheet metal and exhaust especially. Granted, it's not any good for spray-arc, but when you're on your back under a car with barely enough room for the hood - having to manhandle a 300A whip is just one more annoyance.

                  It's actually the main reason I'd like my 130xp back. The small package fitted with .023 would be ideal for doing body work or little repairs. I use .035 as my mainstay, and that simply has too much heat to melt the wire for good success on sheet metal.


                  • #54
                    Home-made welding gas

                    Thanks Jim.

                    As you say - horses for courses. There is no way I'd get my "gun" under a car etc. That is where those better smaller machines perform their magic - in the right hands. Thin "out of position" welding is as hard as it gets - for me anyway. "In position" is OK as I usually "hit and miss" (weld - skip - weld and then go back again etc.) if needs be.

                    I didn't mention changing polarity or inductance as I was not sure that the smaller machines have it.

                    But I am quite looking forward to the "home-made" CO/CO2 welding gas process project leads.


                    • #55
                      Flux core uses opposite polarity of gas shielded so changing polarity is a given on all the machines.

                      The important part of the inert gas arc welding process is not so much the shielding but the way the gas ionizes and forms an arc. Each gas is different and the noble gases are particularly effective in that respect since they are a singular species of atoms and don't take part in the reaction. I wonder what welding with Xenon would be like? Extremely bright I would think.

                      I have some other ideas still including the possibility of applying something to the metal in advance that will evolve gas as it is heated. Calcium carbonate is a prime candidate.
                      Free software for calculating bolt circles and similar: Click Here


                      • #56
                        Originally posted by oldtiffie
                        I agree that on the face of it, those small MIG bottles are a PITA and expensive and all too often have a fixed-rate regulator (of sorts).

                        But for some-one up a ladder or in a roof/small space etc. and who has only domestic-type and/or large volt-drop long lead single-phase low amp power supplies - they are great.
                        Right, they're often marketed as "HVAC" or "plumbing" kits, although I would imagine most air conditioning guys are doing brazing or soldering, and not welding.
                        "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."


                        • #57
                          All the little MIG welders have the ability to reverse polarity, as Evan says, you need to for FC wire. The fluxcore wirefeed welders (which lack the gas valve, and sometimes the whip provisions for gas) have no need to reverse polarity so they often lack the option.

                          Not all 230v machines offer the inductance control. I've never seen a 120v one that did.


                          • #58
                            CO2 Generator

                            Originally posted by Evan
                            Does anybody have plans for a CO2 generator that uses either propane or natural gas to generate mig shielding gas? A quick look online shows they are extremely popular for growing indoor crops. Not what I want or need.
                            Not using combustion for generation, but have you thought of chemical genration? Sulfuric acid on common limestone will certainly work. If you use common garden limestone, which incidentally is rated as high-chemical, (96% CaCO3 or better,) with 66* sulfuric acid, by my calculations, you will generate 2000 liters of CO2 for about $13.00. I pay about $10.00 for a 4 liter jug of acid, and garden limestone is only about $3.00/bag. The trick is to search some chemical history for plans for a Kipp generator. Build it to withstand a bit of pressure, and it will give CO2 at pressure, on demand. When not needed, the generator will just sit there waiting. Further, if you can make it work on the concentrated acid, the gas will be virtually dry. These things USED to be fairly common for any gas that could be generated by adding a liquid to a solid; hydrogen, carbon dioxide, acetylene, chlorine. They have just been forgotten. duffy
                            Duffy, Gatineau, Quebec


                            • #59
                              That had occurred to me but the problem is the availability of H2SO4. I can only buy it in 25 litre bags for battery filling. I have some on hand since I use it for anodizing so I might give it a try.
                              Free software for calculating bolt circles and similar: Click Here


                              • #60
                                At an approximate concentration of 33.5%, would battery acid be suitable?
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