◄If you are using a "cheaper" shielding gas flowmeter/regulator, you likely have one that is pre-set at ~50psi on the outlet that feeds your MIG/TIG welder.
- This pressure is partly responsible for what you have surely noticed as a very high initial flowrate when you squeeze the trigger on your MIG gun, or if TIG welding, when you initiate the gas flow via the solenoid with a footpedal/on-off switch.
- Every time the solenoid closes, the pressure between the regulator/flowmeter and the welding machine's solenoid begins to build up (up to whatever psi the regulator/flowmeter is set to). The higher this pressure, the larger the ID of the hose, and the longer the hose, the more gas volume is stored in the hose (and ultimately wasted).
- The more stops/starts one does, the more times this [waste] occurs because it happens each time the solenoid opens
The sudden, and unnecessary, initial surge of gas, which can be as high as 60 CFH for a split second can add up to some wasted shielding gas over the course of a long project where one has to do a lot of tacks or any other stop/starts. It can be mediated using specialty regulators that are quite expensive, ~$200+ each. There are other solutions like small-orifice hoses to limit gas flow or other flow-controlling devices.
My mod is simple: limit the outlet pressure right after the regulator flowmeter with a standard air pressure regulator to eliminate the surge/spike and thus eliminate the waste gas.
and it works pretty good. Here you can see I have mine at 20psi and for my setup, it works great.
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That air pressure regulator was about $10 on Ebay. Cost of fittings/hose, probably about another $10 worth. I do use 3/16" hose and not ¼".
Probable comments sure to come so I may as well address them ahead of time:
- If the cost of welding gas concerns you, you should charge more for your work
- I don't care about the costs of shielding gas, I can afford it just fine. This, as are many of my other gedankenexperiments, are done just to see if it could be done, and if I'm right about what I think will/will not work.
- Why not just buy Miller/Smith/etc 25psi regulators from the start?
- Because I don't want to
- How much pre-flow do we need?
- No more than the usual, I'd say about 0.3-0.4 seconds, but that's up to you to figure out with your machine/setup..
- Why should we do this?
- No one is twisting your arm, lol
I will say, however, that in stock form, air pressure regulators like this are pretty "dirty" on the inside, even brand new. There is grease/oil from the assembly process that will contaminate the shielding gas with hydrocarbons that will produce soot, especially on aluminum. I did have to take it apart completely and wash every single part in a hot water/dishwashing liquid bath to get rid of all oils/grease. Then I wiped everything down with Q-tips and acetone to make sure everything was nice and clean. Doing so made it good enough for aluminum MIG & TIG from a hobbyist standpoint.
Test runs after cleaning. MIG & TIG on ~3/16" scrap aluminum:
MIG bead was with my HTP Pro Pulse 200 on 035 ER4043 double-pulse synergic program, about 176A.
On the TIG bead, I was using my air-cooled torch @150A on 3/16" aluminum, so it was a little underpowered, and there was a little bit of pepper at the beginning of the puddle, so I took it up to 180A AC and it did clear up the 2nd puddle a smidge more, so for my intents and purposes, it will work just fine for my purposes. A few more amps and perhaps a little more cleaning action and I'm sure it will be fine and dandy. This rod is "Radnor" that I bought from years and years ago, so that says a lot too, lol. I don't do work for aerospace/NASA, so it'll be just fine.
