MIG welding on your car question. [Archive] - GrandAmGT.com Forum

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Pauljp
05-22-2010, 06:17 AM
I have a MIG welder that I have yet to connect the tanks.
So I guess it's not really MIG, but that's besides the point.
Since there is no gas, you have to use flux cored wire and REVERSE THE POSITIVE AND NEGATIVE WIRES.
So, the grounding clamp is actually positive and the wand is negative.
In order to weld on my car, I have to connect the positive clamp to the body somewhere and commence welding.
My question is: could this do anything to all the electronics on the car?
Just to be on the safe side, I disconnected my battery, welded and all was ok.
But did I have to do that?
Has anyone out there MIG welded without the tanks, left the battery connected and had no problems?
I hope I explained this right.
Thanks.

AaronGTR
05-22-2010, 08:44 AM
I understand what you are talking about. There is always a possibility that something could get messed up. They do say to always disconnect the battery when you are welding on the car, as that should stop the flow of power through anything else. They sometimes say to remove things like the PCM and BCM too, but that is a lot of work on these cars. I've welded on my frame before without doing that and everything was fine. Just make sure the battery is disconnected, try and keep the clamp as close to the point where you are welding, and make sure both the clamp location and the spot you are welding have enough clean bare metal to make good contact. That way all the juice you are putting into it should go through those two points.


btw, I highly recommend getting the gas equipment set up when you can. It makes welding so much easier and the quality of the welds so much better. It also opens up the types and thickness of materials and wire you can use. :thumbs: I love my mig setup!

Nick-G
05-22-2010, 12:32 PM
^ x2 I have also welded on the frame of my car without any problems.

Pauljp
05-22-2010, 03:20 PM
^ x2 I have also welded on the frame of my car without any problems.

But were the wires reversed on the welder because you were not using gas shielding? As it is supposed to be on a MIG.
Placing the positive grounding cable on the chassis and welding with the battery still connected, did this cause any problems?
This is what I'm trying to find out.

94gtowner
05-22-2010, 04:29 PM
Why even take the risk of messing anything up? It's not like it's hard to disconnect the battery!

Pauljp
05-22-2010, 05:50 PM
Why even take the risk of messing anything up? It's not like it's hard to disconnect the battery!

That's right. That's exactly what I did for safety.
I'm just wondering if anyone welded with the battery connected and if they had any problems.
I guess for the amount of times you are actually going to weld on your car, it makes sense to take a few seconds to disconnect the battery.
Or get the gas for the MIG and revert back to negative ground welding.

Pauljp
05-22-2010, 07:12 PM
btw, I highly recommend getting the gas equipment set up when you can. It makes welding so much easier and the quality of the welds so much better. It also opens up the types and thickness of materials and wire you can use. :thumbs: I love my mig setup!

Hey Aaron, what mixture of gas do you use?
Do you rent your tanks?
The reason that I don't have any tanks yet is my work space is extremely limited in my tiny house.
Usually I do all my work on the grass beside my place, so lugging around tanks is going to be a pain.
I wonder if you can get disposable tanks like with propane?
I sure would like to try them out.

plastic_indian
05-22-2010, 11:14 PM
I guess for the amount of times you are actually going to weld on your car, it makes sense to take a few seconds to disconnect the battery.
Or get the gas for the MIG and revert back to negative ground welding.

Always disconnect the batt negative side; as you say, it only takes a few seconds. The concern regarding arc welding in the vicinity of microprocessor electronics is not relegated to positive vs. negative ground setups; the concern is for current flow (in either direction) associated with G/SMAW (or GTAW) to cause damage to sensitive components used in solid state electronics. By disconnecting the ground cable, one disassociates any sheetmetal-grounded electronics from the weld process (which is presumably using a sheetmetal ground or hot on the power bus)

As for positive ground welding, I've not known of this in common practice outside of zapping a bulb on the tip of a TIG electrode for aluminum welding. The theory of positive-ground welding is that (based upon the electron theory of electricity) material transfer occurs only from the substrate to the electrode; this is the precise opposite of conventional welding theory (utilizing a fill material). The usage of a shield gas (70/30 Ar/CO2 for MIG, 100% Ar for TIG) is intended to inundate the weld zone with a non-oxidizing environment until the weld puddle cools to solidification, so as to eliminate/greatly reduce the proliferation of occlusions in the weld zone. In short, a negative ground setup tends to transfer fill material (the wire in the case of MIG, fill rod in the case of TIG, electrode rod in the case of SMAW) to the weld puddle. From the hobbyist level through relatively advanced mild steel welding applications, there is no reason to deviate from the shield gas-protected negative ground approach to welding. If you have a stick welder, fine; rely on the flux to keep the weld oxidation-free; if you have GMAW or GTAW equipment, use the proper shield gas; you've invested a considerable amount of money in the equipment, why try to cheat on the cost of shield gas?

Unhook your battery, place your ground clamp as close as possible to the weld zone, and don't try to cheat the shield environment. Follow these guidelines, and with decent equipment and a few weeks of practice, anyone can lay down quality beads without collateral damage.

AaronGTR
05-23-2010, 09:09 AM
Hey Aaron, what mixture of gas do you use?
Do you rent your tanks?
The reason that I don't have any tanks yet is my work space is extremely limited in my tiny house.
Usually I do all my work on the grass beside my place, so lugging around tanks is going to be a pain.
I wonder if you can get disposable tanks like with propane?
I sure would like to try them out.

I buy most of my supplies from here. http://www.airgas.com/ They have a store location close to me so I can pick the stuff up. You'd have to check and see if they have any locations by you, or see if you can find a local welding supply shop. They do have some very small tanks you can rent that don't take up much space. I think they are 40c.f. or something, not sure, but they are the cheapest smallest ones they have, and they fit perfectly on the back of my welder cart. They are only about 8" around and about 2ft tall or so, not big at all. They last long enough for occasional home welding use. The larger tanks are 80/120/160 and are mostly for business and industrial use. You pay a deposit on the tanks, then when you empty one you bring it in to exchange it for a full one and just pay for the gas, which isn't too expensive by itself. Only bad thing about the small tanks is they are somewhat limited in the gas mixtures available, but they have most of what you need. For most steel welding I use 75% argon 25% co2. If I'm welding something thick and need more heat for penetration, or when I'm welding stainless steel, I use 100% argon. It gets the metal hotter than with the co2. Just gotta be careful not to weld too fast and warp the piece. A mix of 90% helium w/argon and co2 for the rest is actually better for stainless, but you can only get it in big tanks. :( That's what I'd get if I had a shop and was welding all the time.


As for positive ground welding, I've not known of this in common practice outside of zapping a bulb on the tip of a TIG electrode for aluminum welding. The theory of positive-ground welding is that (based upon the electron theory of electricity) material transfer occurs only from the substrate to the electrode; this is the precise opposite of conventional welding theory (utilizing a fill material). The usage of a shield gas (70/30 Ar/CO2 for MIG, 100% Ar for TIG) is intended to inundate the weld zone with a non-oxidizing environment until the weld puddle cools to solidification, so as to eliminate/greatly reduce the proliferation of occlusions in the weld zone. In short, a negative ground setup tends to transfer fill material (the wire in the case of MIG, fill rod in the case of TIG, electrode rod in the case of SMAW) to the weld puddle. From the hobbyist level through relatively advanced mild steel welding applications, there is no reason to deviate from the shield gas-protected negative ground approach to welding. If you have a stick welder, fine; rely on the flux to keep the weld oxidation-free; if you have GMAW or GTAW equipment, use the proper shield gas; you've invested a considerable amount of money in the equipment, why try to cheat on the cost of shield gas?


Positive ground welding is very common for the normal "cheap" wire welders. the non-MIG kind that use flux core wire. They are all like that. Once you have shielding gas, you can do the normal negative ground and positive on the wire. One reason it works so much better. The reason most people don't get the MIG setups is cost and space. A flux core wire welder is relatively small and cheap. Conversely, when I bought my MIG welder, it didn't come with any of the equipment for gas and I had to buy that separate. After buying regulators, hoses, a cart, several different types of solid wire, welding gloves, and a helmet.... I had about equaled what I paid just for the welder and doubled my total cost. ;)