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Evan
07-02-2009, 10:43 AM
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.

Alan Smith
07-02-2009, 10:55 AM
Evan, why not use the propane as your shielding gas, you'd certainly get CO2.
And water and soot.

aboard_epsilon
07-02-2009, 11:14 AM
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.


That's right. My wife is in the compressed industrial gas business and sells bottles, not rents them. The actual cost of gases is almost nothing. Most acetylene is made from natural gas and 1000 cubic feet of natural gas was $6.31 on Friday and will make around 300 cubic feet of acetylene as well as CO2 and a bit of helium while providing all the energy needed to run the process. If you assign all the raw material and energy cost to the acetylene then the cost of production, not counting plant amortization, is 2 cents per cubic foot.

why do you need it ..you must get it cheap ..

what about doing some more in-depth study ..on car exhaust gas . lpg car exhaust gas


and another thing ..i thought your MRS was big in grinding wheels ..

all the best.markj

dp
07-02-2009, 11:24 AM
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.

I've been kicking this very thing around for several weeks. I have concluded it is possible to trap the exhaust gas from a torch and to cool and dehumidify it, and then store it in a low-pressure or even high pressure container. The last step is to see what the welds look like. I was thinking there could be a good HSM article in it if it works well.

Evan
07-02-2009, 11:32 AM
I get absolutely no breaks on the gas refills. She is a dealer for a larger company and they don't give discounts to anybody.

lazlo
07-02-2009, 11:32 AM
We had a long thread about DIY CO2 generation (for welding) several months back.

Straight CO2 gives a lousy arc compared with C25. It's hot, fiery arc that creates a ton of spatter. Straight C02 also oxidizes a lot more than C25, so most welding texts warn against using it on aluminum or stainless steel.

I've used straight C02 on structural steel, and it was miserable. It penetrates like crazy though! Never tried it on aluminum.

JCHannum
07-02-2009, 11:37 AM
So, how's Cap & Trade going to work with that?

dp
07-02-2009, 11:40 AM
So, how's Cap & Trade going to work with that?

I don't think anyone has any expectations that Cap and Trade is going to work regarding CO2 levels - it is only supposed to generate tax revenue and limit growth. That, I think, it is where it is going to do very well.

Evan
07-02-2009, 11:42 AM
I figure a propane tank would make a good storage vessel. I'm not sure how important it will be to dry the gas. CO2 breaks down in the arc to carbon and oxygen anyway and water would do the same except for adding some hydrogen. Not sure in what direction the reactions would proceed but in theory you could synthesize nearly any simple hydrocarbon.

dp
07-02-2009, 11:42 AM
We had a long thread about DIY CO2 generation (for welding) several months back.

Straight CO2 gives a lousy arc compared with C25. It's hot, fiery arc that creates a ton of spatter. Straight C02 also oxidizes a lot more than C25, so most welding texts warn against using it on aluminum or stainless steel.

I've used straight C02 on structural steel, and it was miserable. It penetrates like crazy though! Never tried it on aluminum.

I'm pretty sure the gas mix contained in propane exhaust is far from pure CO2 - but what it is isn't exactly clear. Certainly it will have a lot of what air is made of but with higher levels of CO2 and far less oxygen.

dp
07-02-2009, 11:45 AM
I figure a propane tank would make a good storage vessel. I'm not sure how important it will be to dry the gas.

Removing water is just a good way to help the storage tank last longer.

lazlo
07-02-2009, 11:48 AM
I'm pretty sure the gas mix contained in propane exhaust is far from pure CO2 - but what it is isn't exactly clear. Certainly it will have a lot of what air is made of but with higher levels of CO2 and far less oxygen.

The problem is that you need an inert shielding gas for TIG and MIG. So C25, which most people use for MIG, is 75% Argon with 25% C02 added to enhance penetration on steel.

For MIG'ing Aluminum, most people use pure argon, because of the oxidation issues I mentioned.

Evan
07-02-2009, 11:51 AM
Aside from traces of odorants and other LPG molecules the exhaust will be Nitrogen, CO2, virtually no free oxygen and NOx. How much NOX depends on the combustion temperature of the generator flame but to maximize clean gas output you would want a stoichiometric mixture. The largest monomolecular component will be the nitrogen and it will have a small nitriding effect on the weld.

[edit]It certainly won't be the same as using straight CO2.

wierdscience
07-02-2009, 11:54 AM
Evan,does your machine use an adjustable flow meter,or is it the fixed rate kind that comes with the machine?

Reason I ask is the fixed variety are set to a happy medium,but actually waste gas indoors.Having an actual flow meter can save you a third of a bottle welding indoors.

Evan
07-02-2009, 11:56 AM
It's a fully adjustable two stage regulator/flowmeter.

kvom
07-02-2009, 12:01 PM
My 20# CO2 tank costs me less than $20 to refill.

dp
07-02-2009, 12:17 PM
My 20# CO2 tank costs me less than $20 to refill.

Imagine how far that $20 would go if burning propane was an effective alternate. Or natural gas. Especially if that natural gas was also used to heat your shop.

You'd have fuel enough to power your new government mandated green lawn mower, your new efficient Government Motors Chevy, and a couple miles of bead.

Liger Zero
07-02-2009, 12:29 PM
I suspect you'll be using that "miles of bead" to repair your Government Motors truck and your Green Mandate lawnmower.

Optics Curmudgeon
07-02-2009, 01:37 PM
I'll enter a comment on this. There are commercial devices that are used to generate furnace atmospheres by partially combusting natural gas with heat and a catalyst. Depending on the degree of combustion they are referred to as endothermic or exothermic gasses. Endothermic (heat going in) gasses are mostly CO and methane, with some CO2 and hydrogen. Water vapor, of course. Exothermic (generating heat) gasses have a lot more CO2, less CO, almost no methane or hydrogen and a lot more water vapor. An exothermic reactor that burns propane would be an effective CO2 generator, I would think. A big project, but Evan isn't one to avoid that sort of thing. As an aside, I have a tale of an endothermic generator in South Boston. In 1979 I was working for Airco, and with natural gas prices at record highs Airco was selling a furnace atmosphere system that was intended to replace cracked natural gas atmospheres. We went to a sintering plant in Southie and as part of the preparation for conversion we analyzed the gas they were using. These gas generators are typically set up by checking the dew point of the product gas, given that natural gas is very dry, and any water vapor comes from the catalytic reaction. We found that their gas dew point was very high, but a gas chromatograph showed that the other gas constituents were in the proper proportions. WTF?! Having run out of ideas we checked the dew point of the natural gas and found it was quite wet. A call to the gas company and the shocking truth is revealed. The gas mains in that part of town were put in when the gas was manufactured by cooking coal at the gas works, and were made of wood. The manufactured gas had plenty of water vapor, and things were OK until natural gas took over and the mains dried out, cracked and leaked. In addition, dust in the mains got kicked up and clogged jets, etc. Rather than replace the mains the gas company just raised the dew point, 99% of users didn't care and the others adjusted in other ways.

Joe

Evan
07-02-2009, 01:54 PM
I happen to have one item that should make it a reasonably easy job to build a gas generator. Sitting in the garage shop is a brand new catalytic converter that I removed immediately from my Ford Ranger when I bought it new in '88. All it should take is a small pilot burner to get the temperature up to operating condition and then I will have two things. Clean combustion gas and shop heat. Another idea occured to me and that is using the burner from a pulse combustion gas furnace. The only problem with that is I don't have one but it should be close to ideal. The exhaust gas from those can be vented with plastic pipe they are so efficient.

I am going to experiment with this in the near future so I will be reporting on what I find. I don't think it would make a publishable article as there are too many potential liability issues, at least in the US.

deltaenterprizes
07-02-2009, 04:09 PM
I remember seeing a video either on youtube or DIY about a guy doing this but I can't remember how he generated the CO2

aboard_epsilon
07-02-2009, 04:24 PM
I remember seeing a video either on youtube or DIY about a guy doing this but I can't remember how he generated the CO2

from homebrew ..catching it in bin liners then compressing it , and putting it in an LPG bottle.

OK if you are a boozer and have weeks to wait .

jusat had to get a bottle ..i use one bottle a year and it costs me over 100

all the best.markj

gnm109
07-02-2009, 05:07 PM
My 20# CO2 tank costs me less than $20 to refill.


Right. It's very economical. Contrary to the views of some folks, CO2 for mild steel MIG works very nicely for me. Penetration is excellent and, if the tip is kept clean and used with liberal quantities of welding gel, spatter is negligible. I pay $23.00 for a refill on a 20# cylinder that I own.

That's equivalent to 160 cu.ft of Argon or C25 which is closer to $70 out the door. It's an easy decision for me.

doctor demo
07-02-2009, 09:56 PM
I'm not trying to change the subject too much, but for around the home shop, why not use one of the flux core brands like Innershield ?

I use it in My little sp125 and get good results. I also use it at work in a larger version for allmost all of our structural steel requirements . I have not had a weld inspection fail yet(knock on wood) and You don't have to wory about running out of gas after the store closes either.

Steve

Evan
07-03-2009, 01:57 AM
I do use flux core. It spatters and you use twice as much wire that costs twice as much money to do the same amount of welding. It doesn't make as nice a weld and the flux must be completely removed before painting. Other than that it's fine.

andy_b
07-03-2009, 02:24 AM
i'm just wondering, now that CO2 is considered a toxin in the US, would a CO2 generator be classified the same as a mercury generator or a dioxin generator? i wonder if i'll need a hazardous materials transport permit to take my CO2 bottle to be refilled.

andy b.

Willy
07-03-2009, 02:35 AM
Evan those are exactly the reasons I don't use co2 anymore.
I find a lot of wire wasted on spatter and more time wasted on cleanup.
I realized the 75% argon 25% co2 blend isn't cheap, but then neither is my time nor the item I'm welding at any given time.

If I'm really after penetration that a 250amp mig won't do I'll reach for the stick.

I think if you do a feasibility study you'll be time and money ahead by just biting the bullet and do what everyone else in the industry has, and go with the 75/25.
I respect your inclination to travel the road less traveled, but sometimes it can be the long way home.

Jim Shaper
07-03-2009, 02:57 AM
Flux core also produces a LOT of smoke.

There's a time and place for it, as there are various FC electrodes that create alloys due to the elements contained within the flux, but there's a trade off of post weld cleaning that comes with it.

Having used FC indoors - I can honestly say you'd never catch me doing it at my shop ever again. The dust on everything is too much.

Co2 shouldn't cost more than about 15 bucks for a 10# bottle fill. Don't buy it at the LWS, buy it from a dry ice manufacturer. There's a huge market for dry ice in the medical field, and liquid co2 in pop dispensers, so find an outfit that services them to get your co2.

Argon/co2 blends are nice. For the occasional user, the cost increase is part of the cheapest consumables in the process. Even when I tig, I don't think too much about the gas consumption - it's simply not all that relevant. Your arc time per hour is so low in manual processes, that you'd have to go to great lengths to determine how much gas you actually used. 80cf of C25 in MIG will easily last through 20# of wire. How many home shop weldor's is burning through a roll every month? So even if you were, and you were doing it every month and you were paying $40 a fill - you're talking about spending $240 a year on gas. How many of you do work for less than 50 bucks? 5 jobs and your whole year's gas consumption is paid for.

The electricity used is probably more expensive than the shielding gasses. There again, your arc time is typically really low.

I typically get a full 44# spool out of a 125cf tank. That's a lot of weld for my $32 investment in C25 shielding gas.

The last bit of advice is get the biggest tank that makes sense for you. Shielding gas doesn't go bad. Having a couple hundred invested in a giant bottle might make more sense than spending that much every few months in service fees for the refills. Most of what the LWS is charging you is labor on the transaction. The gasses are pretty cheap, but they have to pay the monkey in the back room 20/hr or more to handle your bottle.

wbleeker
07-03-2009, 03:50 AM
You blokes in the states who can own your own bottles do alright, we have to rent ours, at 150 aud for an E size (don't know so don't ask, but the next size down from the big ones here) and about 80 AUD for a refill for CO2 I am paying out 600 AUD a year for the four bottles I have plus the gas I use, some years I use next to none, others several bottles of each.
Will

Swarf&Sparks
07-03-2009, 12:17 PM
Speaking from a position of moderate ignorance here, I weld TIG only with 100% argon (which is NOT cheap here)

I just wonder what the intense UV would do to the kind of reaction at the torch head that Evan suggests?

My only interest in CO2 is carbonating the soda for my whisky.
Believe it or not, it is cheaper for me to keep a bottle of CO2 for carbonation, than to buy bottled soda water at the supermarket.
:D

doctor demo
07-04-2009, 07:44 PM
I do use flux core. It spatters and you use twice as much wire that costs twice as much money to do the same amount of welding. It doesn't make as nice a weld and the flux must be completely removed before painting. Other than that it's fine.

I don't find that it spatters a significant amount more than bare wire with co2.
Given the choice, I usualy choose the flux core over the other processes available to me at work for what I do , it is faster.
I will not dispute Your point about cleaning befor painting but is not a problem, everything that gets inspected needs to be wire wheeled or the inspector gets pi$$y. Stuff that does not require an inspection gets preped for paint by the painting contractor or if it doesn't need paint it doesn't get cleaned .
As far as weld bead cosmetics , flux core looks just as good or better than bare wire ....for me any way.
I guess it comes down to personal preference, and not having a co2 bottle at home gives me more room for other junk:D .

Steve

Evan
07-04-2009, 09:36 PM
So far my limited experience with mig vs flux core is that the mig is much more controllable when welding thin wall tubing. I do a lot of that. My iron work gates and railings are largely constructed of thin wall tubing so that they don't weigh a hundred pounds per yard. Plus, I have a reliable source of decent quality thin wall square tubing shorts that average 4 to 6 feet long and cost me nothing. I don't know how fuel gas exhaus will compare to argon/CO2 but I think I will find out. I'll start with something very simple just as a test to see if it is worth proceeding. In fact, I just had an idea....

Back in a bit.

barts
07-04-2009, 10:10 PM
i'm just wondering, now that CO2 is considered a toxin in the US, would a CO2 generator be classified the same as a mercury generator or a dioxin generator? i wonder if i'll need a hazardous materials transport permit to take my CO2 bottle to be refilled.

andy b.

Pardon? CO2 considered a toxin? Stop making stuff up. It's a pollutant - a resource in the wrong place.

- Bart

Evan
07-04-2009, 10:25 PM
I just did a very quick and dirty test. This may be enough to make me reconsider spending any more time on this idea.

The three beads on the right were laid with no shielding gas, just mig wire.

The three beads in the centre were done with gas on.

The three on the left were done with the gas off and the tail of a propane bottle torch flame playing over the puddle. Yuck.

http://ixian.ca/pics6/weld_beads.jpg

Willy
07-05-2009, 04:51 PM
Thanks for the update Evan, and showing us the results of your research.
Interesting, I would of thought that the weld beads without any shielding gas would have been the worst.
What kind of shielding gas was used on the center beads?

Although I have this information at home in print, I thought I would share this site for those that need a a comprehensive guide to shielding gas characteristics and their applications.

http://www.thefabricator.com/Consumables/Consumables_Article.cfm?ID=1702

Evan
07-05-2009, 05:16 PM
The shielding gas is standard argon 75%/CO2 25%

I am going to try again with a little bit more sophistcated setup. Since the flame was impinging on the weld it may be a problem with highly reactive atomic oxygen present in the flame. When I have time I will run the flame into a can and take the exhaust gas from there. One may speculate all day what will happen but until it is actually tried nobody really knows.

I have another idea to try as well.

macona
07-05-2009, 05:28 PM
Also turbulence from the flame may be drawing atmosphere into the weld zone.

aboard_epsilon
07-05-2009, 05:41 PM
try running an IC engine on propane ..and use the exhaust ..

a ic generator would do ..all you have to do is run a pipe into the air intake and they will run ..

all the best.markj

dp
07-06-2009, 10:29 PM
My 20# CO2 tank costs me less than $20 to refill.

I was at the local HF store yesterday and noticed they have 20 cu ft argon and CO/2 bottles. They seem quite small - is that a good way to go? Seems very limiting, but I've never tried gas with my MIG. They were certainly cheap - I assume they are empty when purchased.

Evan
07-06-2009, 11:34 PM
That is what I have. I had a spare oxy B bottle and had it re-valved for argon. It cost less than half what a new tank would cost. The valve cost $45 and the fill was about the same. It seems to be lasting pretty well.

The thing that surprised me is how much longer a spool of wire lasts. It's about half the price of flux core and lasts twice as long. I just bought a 5 kilo spool of .025 mig wire for $40. It's Lincoln brand, I hope my Miller doesn't decide to pout.

dp
07-06-2009, 11:48 PM
I just bought a spool of the ni-rod flux core stuff. Shipping weight is 30lbs so I think that's more than I'll need in a lifetime. When is your star party? :)

lazlo
07-06-2009, 11:59 PM
I was at the local HF store yesterday and noticed they have 20 cu ft argon and CO/2 bottles. They seem quite small - is that a good way to go?

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.

wierdscience
07-07-2009, 12:01 AM
That is what I have. I had a spare oxy B bottle and had it re-valved for argon. It cost less than half what a new tank would cost. The valve cost $45 and the fill was about the same. It seems to be lasting pretty well.

The thing that surprised me is how much longer a spool of wire lasts. It's about half the price of flux core and lasts twice as long. I just bought a 5 kilo spool of .025 mig wire for $40. It's Lincoln brand, I hope my Miller doesn't decide to pout.

Yep,solid wire is a better deal all the way round.

On the gas problem,several years ago I needed a c25 bottle and the then only show in town would not lease a bottle without a good credit rating(I haven't borrowed any money in years so I didn't have a rating).

My solution was to use my own bottle and buy gas off a local weld shop.Two argon fittings on each end of a short piece of hydraulic hose was all I needed to transfer to my bottle.My bottle was the same size as what they used (175cf) so they just charged me for half a bottle +$10 for they're trouble.A full bottle ran 1900psi so I ended up with 900# give or take,enough to burn a 11# roll of .030" ER70 with a little left over.

Maybe talk to a local fab shop?

Jim Shaper
07-07-2009, 12:17 AM
I'm also surprised by how clean the bare wire beads look.

What machine did you do that with, and what were your settings?

If you try that over 100A, you end up with what looks like bird chit.

Evan
07-07-2009, 01:07 AM
I'm also surprised by how clean the bare wire beads look.


Why? Gas welding doesn't have any better shielding than just the combustion fumes. I have done a lot of O/A welding over the years and I tend to use the same technique with the wirefeed. I did some more tests without gas and the weld beads are almost respectable. It runs sort of hot without the gas but the main thing is that it doesn't flow out like it does with flux or gas. Still, it would work in a pinch even without gas.

The three beads on the right are at different voltages, no gas. I have a Miller 135.

The next bead to the left was done in a rich propane atmosphere with the mixing ports on the torch taped over. Blecch.

Further to the left are several beads that were done with the metal first painted with borax. Also not good. What I haven't tried yet is reversing the polarity. That may make a major difference.

http://ixian.ca/pics6/mignogas.jpg

oldtiffie
07-07-2009, 01:34 AM
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.

Jim Shaper
07-07-2009, 01:36 AM
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.

dp
07-07-2009, 01:36 AM
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.

Evan
07-07-2009, 03:08 AM
Jim,

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.

http://metalshopborealis.ca/pics2/welds2.jpg

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.

oldtiffie
07-07-2009, 03:25 AM
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.

Lazlo.

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.

Jim Shaper
07-07-2009, 03:26 AM
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.

oldtiffie
07-07-2009, 04:08 AM
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!!!

Jim Shaper
07-07-2009, 04:29 AM
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. :D (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.

oldtiffie
07-07-2009, 06:40 AM
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.

Evan
07-07-2009, 07:07 AM
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.

lazlo
07-07-2009, 12:51 PM
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.

Jim Shaper
07-07-2009, 02:09 PM
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.

Duffy
07-07-2009, 07:34 PM
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

Evan
07-07-2009, 08:11 PM
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.

Willy
07-07-2009, 08:32 PM
At an approximate concentration of 33.5%, would battery acid be suitable?

gnm109
07-07-2009, 09:55 PM
I was at the local HF store yesterday and noticed they have 20 cu ft argon and CO/2 bottles. They seem quite small - is that a good way to go? Seems very limiting, but I've never tried gas with my MIG. They were certainly cheap - I assume they are empty when purchased.


Those are really quite small. You'd be changing them frequently.

oldtiffie
07-07-2009, 10:56 PM
There would not be much that is more expensive in terms of cu.ft/$ than those small bottles, but in terms of convenience - small jobs and/or small spaces etc. and no need to fill and buy larger bottles - there isn't much better.

You should seriously consider a "real (good)" regulator for them - not all that expensive instead of the standard "fixed" (so-called) regulator.

The question - more often than not - is more why you should buy them rather than why you should not.

There are some very good plusses and minuses either way depending upon your circumstances.

But if you use a fair bit of gas in your shop, those smaller bottle prices will very soon make you realise that the "expensive" gas that everybody seems to be bitching about is not so expensive after all.

I have only see argon and CO/CO2. I can't recall seeing the best all-round gas for steel - 75/25.

Evan
07-08-2009, 12:44 AM
75/25 is Argon/CO2. The price of Argon and CO2 is a complete rip off. Argon is a side product from liquefying air to obtain oxygen and it isn't exactly rare either. Every cubic metre of atmosphere contains a litre of argon gas. We all know how easy CO2 is to obtain, in fact it is usually made as a by product of producing acetylene from natural gas. Unlike acetylene neither argon or CO2 are toxic, explosive, or difficult to transport. The only hazard involved at all is gas under pressure and there is no local ecological consequence from a release of either in common circumstances. The training to handle the products for sale is minimal, I have had it.

Those two gases in particular undoubtedly reap by far the highest profit margin of any of the industrial compressed gases with the possible exception of nitrogen. I would expect that the profit margin from production to retail sale is on the order of 2000 percent or more. Keep in mind that these gases are by products of the production of other gases and when in excess are simply vented. Because of this it is unlikely that plant amortization is applied to the cost of production.

oldtiffie
07-08-2009, 03:55 AM
I can not care less about "rip-offs" as me upsetting either myself or anyone else needlessly over something I either can't or won't do anything about is - in my opinion - an exercise in futility and stupidity on my part.

Its either what I want for what I am prepared to pay on the day - or not. If it is a $10 item and I want it at that price. I buy it - couple of $ either way is of no concern. If was it "upped" to $100 and its essential that I have it - then I pay for it and use it. Sometimes that $100 was a good buy as there have been occasions which warranted paying $200 or more - with possibly more to come.

I can't see the sense either in spending hours trawling the net or burning fuel and wasting time if it is urgent in the car just to save a couple of $ when it is available locally just for a few minutes trip - or even to have it delivered.

It depends entirely on the circumstances and my judgment at the time.

After I've bought it, its in the past and nothing will change it. I just - if needed - shrug my shoulders and move on.

I just cannot see the sense in worrying needlessly.

oldtiffie
07-08-2009, 04:32 AM
Read from page 57 onward for shielding gas recommendations in this BOC (AU = OZ) pdf file.

https://boc.com.au/boc_sp/au/downloads/reference_manuals/industrial/BOC_IPRM_S03-IndGas.pdf

I will hunt out and post some other stuff shortly as regards MIG weld shielding gases and will
post them later.

aboard_epsilon
07-08-2009, 11:38 AM
I can't see the sense either in spending hours trawling the net or burning fuel and wasting time if it is urgent in the car just to save a couple of $ when it is available locally just for a few minutes trip - or even to have it delivered.

delivered ..hmmm

in the UK you pick it up from the the dealer ..and BOC tags another delivery charge (fixed charge) on top of the gas price ..

what you got for one bottle IN THE UK IS is :-

BOC argoshield light size Y... 4.8 cubic metres

1 bottle

YEARLY RENTAL; 81.,70

the gas in it ..

34.85 plus 5.23 vat .. = 40.08
environmental energy surcharge 0.45
fixed charges on it 11.35 plus 1.70 vat =13.05
equals 55.88 for the gas in the bottle

so YEARLY RENTAL; 81.,70 plus 55.88 for the gas in one bottle

1 bottle costs me 137 or $220 a year ..

you seam to have more time than me Evan ..glad you're on the case

all the best.markj

Tilaran
01-20-2014, 08:54 PM
We had a long thread about DIY CO2 generation (for welding) several months back.

Straight CO2 gives a lousy arc compared with C25. It's hot, fiery arc that creates a ton of spatter. Straight C02 also oxidizes a lot more than C25, so most welding texts warn against using it on aluminum or stainless steel.

I've used straight C02 on structural steel, and it was miserable. It penetrates like crazy though! Never tried it on aluminum.
Stick with machining. You have no business MIG welding.

loose nut
01-21-2014, 09:02 PM
You do know that this thread finished 5 years ago don't you.