MIG welding 101/welding cart project
07-11-2008, 10:54 PM
#1
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First, an introduction to MIG welding.
Theres already a post giving info on what to look for in a mig welder, so Ill start this assuming that you already have a MIG welder, and have familiarized with the controls. For mild steel, use an argon/C02 mix. For stainless, argon/C02 will yield the strongest weld, but it will be discolored. For pretty welds in stainless where strength is not the utmost concern, use pure argon.
Setting up the machine:
I cant give guides for every machine here, so its up to you to figure it out. Most welders come with a cheat sheet, my hobart has one in the inside of the door on the side of the machine you open to access the wire roll. But even still those guides are just a good starting point. What is really important is getting adequate penetration at a welding speed you are comfortable with. If you weld fast, you need to run a higher amperage setting, while if you want to go slower, you can get away with less. A good test is take a scrap piece of the same thickness, and run a few beads on it. Keep turning up the amperage until you burn a hole in the piece, then back it off one step. Ideally, you want the weld to just penetrate the back side of the piece you are welding.
Setting the wire speed is very important to getting a good weld. No matter what, you cannot get a smooth weld bead if you do not have a stable arc. If the arc is unstable, the wire speed is wrong. If the wire is burning back towards the tip, increase the feed speed. If the wire is feeding past the weld puddle, and pushing the gun off the workpiece, turn the wire speed down. The arc should sound like bacon in a frying pan, and if you look closely, the wire should be melting at the same point off the nozzle. Good news is there is a range of speeds that will provide a stable arc. With very tight fitting joints, you want to use a lower speed so you dont create an excessively large bead. For filling gaps, you want it about as high as you can get a stable arc, to get as much material down as quickly as possible. Experience is golden here, just practice, practice, practice.
Gas flow:
If your regulator has a flow gauge on it, 20-30 cubic feet per hour is the normal range. If you keep the nozzle close to the work piece, you can use the lower end of the range, but the farther away it is, the more flow you need to get adequate shielding. If you are getting porous welds, check the gas flow. Provided the pieces are clean, insufficient gas flow is usually yhe cause of porous welds.
wire choice:
Its pretty easy, there arent many options. ER70S is the standard for mild steel, ER308L is the standard for stainless. Theres 2 different alloys for MIG welding aluminum, but I think that deserves its own thread. MIG, while possible, is not a practical choice for aluminum.
Theres already a post giving info on what to look for in a mig welder, so Ill start this assuming that you already have a MIG welder, and have familiarized with the controls. For mild steel, use an argon/C02 mix. For stainless, argon/C02 will yield the strongest weld, but it will be discolored. For pretty welds in stainless where strength is not the utmost concern, use pure argon.
Setting up the machine:
I cant give guides for every machine here, so its up to you to figure it out. Most welders come with a cheat sheet, my hobart has one in the inside of the door on the side of the machine you open to access the wire roll. But even still those guides are just a good starting point. What is really important is getting adequate penetration at a welding speed you are comfortable with. If you weld fast, you need to run a higher amperage setting, while if you want to go slower, you can get away with less. A good test is take a scrap piece of the same thickness, and run a few beads on it. Keep turning up the amperage until you burn a hole in the piece, then back it off one step. Ideally, you want the weld to just penetrate the back side of the piece you are welding.
Setting the wire speed is very important to getting a good weld. No matter what, you cannot get a smooth weld bead if you do not have a stable arc. If the arc is unstable, the wire speed is wrong. If the wire is burning back towards the tip, increase the feed speed. If the wire is feeding past the weld puddle, and pushing the gun off the workpiece, turn the wire speed down. The arc should sound like bacon in a frying pan, and if you look closely, the wire should be melting at the same point off the nozzle. Good news is there is a range of speeds that will provide a stable arc. With very tight fitting joints, you want to use a lower speed so you dont create an excessively large bead. For filling gaps, you want it about as high as you can get a stable arc, to get as much material down as quickly as possible. Experience is golden here, just practice, practice, practice.
Gas flow:
If your regulator has a flow gauge on it, 20-30 cubic feet per hour is the normal range. If you keep the nozzle close to the work piece, you can use the lower end of the range, but the farther away it is, the more flow you need to get adequate shielding. If you are getting porous welds, check the gas flow. Provided the pieces are clean, insufficient gas flow is usually yhe cause of porous welds.
wire choice:
Its pretty easy, there arent many options. ER70S is the standard for mild steel, ER308L is the standard for stainless. Theres 2 different alloys for MIG welding aluminum, but I think that deserves its own thread. MIG, while possible, is not a practical choice for aluminum.
07-11-2008, 11:46 PM
#2
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Join Date: Sep 2002
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Welding cart:
Making your own welding cart is a great beginner fab project. The material we will be using is readily available, relatively cheap, and thick enough that theres a lot of room for error that wont affect the structural integrity. But that being said, I still urge you to do the best you can. I did mine out of 1" x 1/8" thick angle iron. Folding bed frames, if you can find them are a very cheap source of the necessary angle iron. Im not going to post a blueprint or anything, because the dimensions will differ from welder to welder, but I will post the dimensions mine came out to.
Cutting: the pieces can be cut in a variety of ways, including a metal bandsaw and an electric angle grinder with cutting wheels. I prefer the latter, since i use mine for a lot of cuts you cant do on a bandsaw. But for this simple project, a bandsaw will work fine, as will almost any other method that can cut the metal with decent accuracy. Angles can be measured with an angle finder or a speed square. As with the cutting tool, use what you are comfortable with.
Welding gas bottles: an important part, and the main reason I decided to make my own cart was to have 2 gas bottles on one cart. I have an argon/C02 mix as well as pure argon. The 90 and 160 cf bottles have an OD of 7" to 7 1/4". I made mine with 1/8" x 2" steel rings at the bottom to locate the bottle, and another at the top to clamp it in place. An easy to form the rings is to lay it out on a piece of plywood with a protractor, then cut it out with a jigsaw. You can easily form the mild steel flat bar around the plywood cutout. Dont count on just making the ends meet and welding it, you are going to have to bend it to very close to the final shape.
Well, they say a picture is worth a thousand words...
I cut the 4 pieces that defined the perimeter of the bottom first, and used a framing square to square it up. Tack weld the pieces in at least 2 places at each joint, then go back and finish weld everything. Then I added the 2 bars that support the gas bottles, with are 3/4" .065 wall steel tubing. Then I made the upper part, which supports the welder in the same way. I made the base a few inches wider, and longer by enough to allow clearance for the welding bottles. The base being wider than the welder gives it stability, remember the pontiac "wider is better" commercials? Once the base and the top(where the welder sits) are welded, I added the 2 uprights to the front of the base, using a framing square to square them up to the base. Once those 2 uprights are in, I tacked the top onto those uprights, at approximately the angle I wanted the welder to sit at. Angling the front of the welder up makes it easier to see/reach the controls when standing. From there, I measured and cut the rear uprights and tacked them in place. If you are satisfied with the position and angle of the welder, finish welding the uprights to the base and top. When measuring for height, remember to account for the height of the wheels, which we will add last..
So now you have a base and a top that your welder can sit on top of. Now its time to make the brackets to secure the gas bottles. I formed the rings for the bottom about 1/4" bigger than the OD of the bottles. My argon bottle is 7" OD, while the argon/C02 is 7 1/4" OD, both being 160 cf. The 90 CF bottles should be 7" OD. But you should double check yours as they may not be identical. Once you have the lower rings, space them evenly on the cross rails, and weld in place. Now its time to make the upper support. I used the actual bottles for this, but the utmost care should be taken. With 2000 PSI in a full bottle, if one falls over and breaks the valve, it can and will go through a wall(or many), and/or anything in its way. I started with the 2 angle brackets that go from the top(where the welder sits) to about 1/8" away from a bottle sitting naturally in the rings we previously made and welded to the base. With the 2 angle iron pieces defining the outermost edge of the fixed part of the upper bottle mount, make a "W" shaped bracket(for 2 bottles, just half round for one) between them that fits tightly to the angle iron. I used 1/8" x 1 1/4" steel bar for this part. Tack it in place, remove the bottle(s) and finish welding. Then using the same 1/8" bar, make a strap that goes around the bottle(s) and back over about 2" of the angle iron brackets to the bottle. Then clamp that strap in place, and drill through both the strap and the angle iron on both sides, and make sure its tight to the bottle(s). Then weld a nut to the inside of the angle centered over the hole. You will then use that to bolt the strap to the back half of the upper bottle mount.
Now all you have to do is get some wheels with a steel base(pretty much everything), and a few short welds are all thats necessary to secure the wheels to each corner of the base.
If you have any questions, or anything you would like me to elaborate on, or take pics of, or whatever, let me know. I was trying to not be specific on measurements because fab work isnt about working off plans. Its every bit as much about working out how to get from point A to point B as it is doing the actual work. Im more trying to guide you through the process, and get you thinking the right way. All fabrication is just being able to figure out what you need to do to get from where you are to where you want to be. Anyone can cut and weld, but what makes a fabricator special is they dont need instructions.
Making your own welding cart is a great beginner fab project. The material we will be using is readily available, relatively cheap, and thick enough that theres a lot of room for error that wont affect the structural integrity. But that being said, I still urge you to do the best you can. I did mine out of 1" x 1/8" thick angle iron. Folding bed frames, if you can find them are a very cheap source of the necessary angle iron. Im not going to post a blueprint or anything, because the dimensions will differ from welder to welder, but I will post the dimensions mine came out to.
Cutting: the pieces can be cut in a variety of ways, including a metal bandsaw and an electric angle grinder with cutting wheels. I prefer the latter, since i use mine for a lot of cuts you cant do on a bandsaw. But for this simple project, a bandsaw will work fine, as will almost any other method that can cut the metal with decent accuracy. Angles can be measured with an angle finder or a speed square. As with the cutting tool, use what you are comfortable with.
Welding gas bottles: an important part, and the main reason I decided to make my own cart was to have 2 gas bottles on one cart. I have an argon/C02 mix as well as pure argon. The 90 and 160 cf bottles have an OD of 7" to 7 1/4". I made mine with 1/8" x 2" steel rings at the bottom to locate the bottle, and another at the top to clamp it in place. An easy to form the rings is to lay it out on a piece of plywood with a protractor, then cut it out with a jigsaw. You can easily form the mild steel flat bar around the plywood cutout. Dont count on just making the ends meet and welding it, you are going to have to bend it to very close to the final shape.
Well, they say a picture is worth a thousand words...
I cut the 4 pieces that defined the perimeter of the bottom first, and used a framing square to square it up. Tack weld the pieces in at least 2 places at each joint, then go back and finish weld everything. Then I added the 2 bars that support the gas bottles, with are 3/4" .065 wall steel tubing. Then I made the upper part, which supports the welder in the same way. I made the base a few inches wider, and longer by enough to allow clearance for the welding bottles. The base being wider than the welder gives it stability, remember the pontiac "wider is better" commercials? Once the base and the top(where the welder sits) are welded, I added the 2 uprights to the front of the base, using a framing square to square them up to the base. Once those 2 uprights are in, I tacked the top onto those uprights, at approximately the angle I wanted the welder to sit at. Angling the front of the welder up makes it easier to see/reach the controls when standing. From there, I measured and cut the rear uprights and tacked them in place. If you are satisfied with the position and angle of the welder, finish welding the uprights to the base and top. When measuring for height, remember to account for the height of the wheels, which we will add last..
So now you have a base and a top that your welder can sit on top of. Now its time to make the brackets to secure the gas bottles. I formed the rings for the bottom about 1/4" bigger than the OD of the bottles. My argon bottle is 7" OD, while the argon/C02 is 7 1/4" OD, both being 160 cf. The 90 CF bottles should be 7" OD. But you should double check yours as they may not be identical. Once you have the lower rings, space them evenly on the cross rails, and weld in place. Now its time to make the upper support. I used the actual bottles for this, but the utmost care should be taken. With 2000 PSI in a full bottle, if one falls over and breaks the valve, it can and will go through a wall(or many), and/or anything in its way. I started with the 2 angle brackets that go from the top(where the welder sits) to about 1/8" away from a bottle sitting naturally in the rings we previously made and welded to the base. With the 2 angle iron pieces defining the outermost edge of the fixed part of the upper bottle mount, make a "W" shaped bracket(for 2 bottles, just half round for one) between them that fits tightly to the angle iron. I used 1/8" x 1 1/4" steel bar for this part. Tack it in place, remove the bottle(s) and finish welding. Then using the same 1/8" bar, make a strap that goes around the bottle(s) and back over about 2" of the angle iron brackets to the bottle. Then clamp that strap in place, and drill through both the strap and the angle iron on both sides, and make sure its tight to the bottle(s). Then weld a nut to the inside of the angle centered over the hole. You will then use that to bolt the strap to the back half of the upper bottle mount.
Now all you have to do is get some wheels with a steel base(pretty much everything), and a few short welds are all thats necessary to secure the wheels to each corner of the base.
If you have any questions, or anything you would like me to elaborate on, or take pics of, or whatever, let me know. I was trying to not be specific on measurements because fab work isnt about working off plans. Its every bit as much about working out how to get from point A to point B as it is doing the actual work. Im more trying to guide you through the process, and get you thinking the right way. All fabrication is just being able to figure out what you need to do to get from where you are to where you want to be. Anyone can cut and weld, but what makes a fabricator special is they dont need instructions.
07-12-2008, 10:32 AM
#4
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Join Date: Feb 2003
Location: Calgary
Posts: 564
Good general write up.. A couple of things I would add is that 20-30 cfh is huge, smaller machines can live at 10-15 especially welding indoors with clean tips and your bottles will last alot longer.. Mig doesn't like drafts at all, even exhaust fans and garage furnaces will make the weld full of holes, if its drafty use a stick welder or put up a temp shield for the weld.
And on buying a machine, stay away from the consumer store specials, and don't expect to weld aluminium with a standard mig machine below 150 amps. Its just not gonna happen. The wire is going to birds nest up in the rollers, and it won't weld anything more than 1/16th of an inch thick.
The machine MS7 has shown there is a good machine for lighter end steel stuff, I had one like that the H135, you can tack stuff up under a car without having to do a pile of adjustments, its got a decent amount of power and Hobart(miller) stuff is built to last. There are all sorts of off-shore Italian and Chinese stuff, and its junk, I have bought it in the past it just doesnt last or work that well, a transformer is a transformer but the quality is in the wirefeeding mechanism.
You can under buy a welder and overbuy as well, I have been guilty of both. The best machine for serious car fabrication work is probably the older millermatics in 200- 250a range. They dont have all the BS on them, yet it has enough adjustability to everything well with a simple setup, and you can spool gun it with a module.
The MM251 was the machine I really wanted as it can do spray transfer, but there was no stock. I ended up with a millermatic 350p with the bernard and spoolgun. Its a great machine for any kind of fabrication work, but you can't just turn it on to quick tack something, every weld has to be programmed, although you can switch between both guns with just a double trigger pull. The integration of computers into mig machines has given the machine to make high quality welds but, the machine is now 3 times slower to setup.
My last piece of advice is don't bother with an auto tint helmet. They are nice for allowing initial positioning and such but they often dont shade dark enough, if your glove momentarily blocks the weld flash they turn off mid weld. They can flicker on and off so fast you dont pick it up, your eyes will automatically turn away for a split second then back to the weld, your welding hand follows your eyes, if your eyes are darting around your weld will follow. My long weld straight line tracking improved 10 fold when I went back to the old manual flip helmet.
And on buying a machine, stay away from the consumer store specials, and don't expect to weld aluminium with a standard mig machine below 150 amps. Its just not gonna happen. The wire is going to birds nest up in the rollers, and it won't weld anything more than 1/16th of an inch thick.
The machine MS7 has shown there is a good machine for lighter end steel stuff, I had one like that the H135, you can tack stuff up under a car without having to do a pile of adjustments, its got a decent amount of power and Hobart(miller) stuff is built to last. There are all sorts of off-shore Italian and Chinese stuff, and its junk, I have bought it in the past it just doesnt last or work that well, a transformer is a transformer but the quality is in the wirefeeding mechanism.
You can under buy a welder and overbuy as well, I have been guilty of both. The best machine for serious car fabrication work is probably the older millermatics in 200- 250a range. They dont have all the BS on them, yet it has enough adjustability to everything well with a simple setup, and you can spool gun it with a module.
The MM251 was the machine I really wanted as it can do spray transfer, but there was no stock. I ended up with a millermatic 350p with the bernard and spoolgun. Its a great machine for any kind of fabrication work, but you can't just turn it on to quick tack something, every weld has to be programmed, although you can switch between both guns with just a double trigger pull. The integration of computers into mig machines has given the machine to make high quality welds but, the machine is now 3 times slower to setup.
My last piece of advice is don't bother with an auto tint helmet. They are nice for allowing initial positioning and such but they often dont shade dark enough, if your glove momentarily blocks the weld flash they turn off mid weld. They can flicker on and off so fast you dont pick it up, your eyes will automatically turn away for a split second then back to the weld, your welding hand follows your eyes, if your eyes are darting around your weld will follow. My long weld straight line tracking improved 10 fold when I went back to the old manual flip helmet.
07-12-2008, 11:10 AM
#5
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My welder there is a Hobart handler 187. 220v, 185 amp. Its got enough power to do anything car related in a single pass, yet its still light enough you can do .035 wall stainless if you are careful. Ive done the aluminum conversion, and am running .035 wire, and oversize tips, and I still get a lot of birds nests. Aluminum wire just doesnt feed reliably pushing through 10 feet of tubing, no matter what precautions you take. Dual drive guns are the way to go for MIG welding aluminum. Not as bulky as a spool gun, but feeds as good as one.
My welder recommended 30 cfh, which I thought was high too. But anything below 20 I have a hard time getting clean welds with, even in still air. I usually stick with 25 cfh.
My welder recommended 30 cfh, which I thought was high too. But anything below 20 I have a hard time getting clean welds with, even in still air. I usually stick with 25 cfh.
07-14-2008, 11:06 PM
#6
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Join Date: Feb 2003
Location: Calgary
Posts: 564
Originally Posted by mazdaspeed7' post='904510' date='Jul 12 2008, 09:10 AM
My welder there is a Hobart handler 187. 220v, 185 amp. Its got enough power to do anything car related in a single pass, yet its still light enough you can do .035 wall stainless if you are careful. Ive done the aluminum conversion, and am running .035 wire, and oversize tips, and I still get a lot of birds nests. Aluminum wire just doesnt feed reliably pushing through 10 feet of tubing, no matter what precautions you take. Dual drive guns are the way to go for MIG welding aluminum. Not as bulky as a spool gun, but feeds as good as one.
My welder recommended 30 cfh, which I thought was high too. But anything below 20 I have a hard time getting clean welds with, even in still air. I usually stick with 25 cfh.
My welder recommended 30 cfh, which I thought was high too. But anything below 20 I have a hard time getting clean welds with, even in still air. I usually stick with 25 cfh.
The spool gun is suprisingly easy to handle, the coolest thing with it, is gun on demand, I never have to unplug either gun, or change wire, just double click the trigger of the gun I want to use, and the welder automatically reverts to the settings for the gun chosen. Its very useful on a mixed metal project, one welder, 2 different materials, or if you have 2 different grades of aluminium, its easier to change the 4lb spools.
I had an SIP that came with an aluminium package, it didnt work at all, I spent more time unravelling wire than ever welding,actually that welder wasnt very good at anything. I wouldnt stray out of the Miller/hobart,Lincoln(real),Esab,Panasonic circles.
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