GMAW 101: Setting the Correct Parameters Unless you weld for a living, it is often difficult to know if your MIG welder is setup for optimal performance. If you find yourself asking questions such as "Am I using the proper voltage? Do I have too much or too little wire? Am I traveling at the right speed?" this article is for you! First we will touch on the basics of properly setting up your welder, and then look what your weld bead is telling you. Equipment Good equipment makes gas metal arc welding easier. Poor equipment can cost you dearly in frustration and weld quality. Recent technology advancements, such as some welding machines' ability to set optimal parameters automatically based on material thickness and wire diameter, allow you to focus on proper technique while achieving smooth, spatter-free starts, a common problem area for occasional welders; however, not all welding machines have this capability. To determine which welding machine and technology suit you the best, find a local welding supply distributor that has an on-site welding lab or will allow you to test-drive a machine before buying one. Getting the Most from Your Machine Regardless of your power source choice, read your owner's manual. It contains important information about proper operation and safety guidelines. Most companies offer their manuals online. The following basic guidelines are for welding steel with solid wire. Aluminum and flux-cored welding require separate discussion. Joint design, position, and other factors affect results and settings. When good results are achieved, record the parameters. 1. Material thickness determines amperage. As a guideline, each 0.001 inch of material thickness requires 1 amp: 0.125 in. = 125 amps. 2. Select proper wire size, according to amperage. Since you don't want to change wire, select one for your most commonly used thicknesses. * 30-130 A: .023-in. * 40-145 A: 0.030 in. * 50-180 A: 0.035 in. * 75-250 A: 0.045 in. 3. Set the voltage. Voltage determines height and width of bead. If no chart, manual or specifications are available for setting the correct voltage, you can try this: while one person welds on s**** metal, an ***istant turns down the voltage until the arc starts stubbing into the work piece. Then, start welding again and have an ***istant increase the voltage until the arc becomes unstable and sloppy. A voltage midway between these two points provides a good starting point. There is a relationship between arc voltage and arc length. A short arc decreases voltage and yields a narrow, "ropey" bead. A longer arc (more voltage) produces a flatter, wider bead. Too much arc length produces a very flat bead and a possibility of an undercut. 4. Set the wire feed speed. Wire speed controls amperage, as well as the amount of weld penetration. A speed that's too high can lead to burn-through. If a manual or weld specification sheet is not available, use the multipliers in the following chart to find a good starting point for wire feed speed. For example, for 0.030-in. wire, multiply by 2 in. per amp to find the wire feed speed in inches per minute (IPM). Examining the Beads One way to check your parameters is by examining the weld bead. Its appearance indicates what needs to be adjusted. Good Weld (Figure 1)-Notice the good penetration into the base material, flat bead profile, appropriate bead width, and good tie-in at the toes of the weld (the edges where the weld metal meets the base metal). <TABLE width=79 border=0><TBODY><TR vAlign=top><TD width=114></TD></TR><TR vAlign=top><TD height=14>Figure 1 </TD></TR></TBODY></TABLE> Voltage Too High (Figure 2)-Too much voltage is marked by poor arc control, inconsistent penetration, and a turbulent weld pool that fails to consistently penetrate the base material. <TABLE width=440 border=0><TBODY><TR vAlign=top><TD width=100 height=218></TD><TD width=100>Figure 2 </TD></TR></TBODY></TABLE> Voltage Too Low (Figure 3)-Too little voltage results in poor arc starts, control and penetration. It also causes excessive spatter, a convex bead profile, and poor tie-in at the toes of the weld. <TABLE width=443 border=0><TBODY><TR vAlign=top><TD width=331></TD><TD width=102>Figure 3 </TD></TR></TBODY></TABLE> Travel Speed Too Fast (Figure 4)-A narrow, convex bead with inadequate tie-in at the toes of the weld, insufficient penetration, and an inconsistent weld bead are caused by traveling too fast. <TABLE width=455 border=0><TBODY><TR vAlign=top><TD width=335 height=234></TD><TD width=110>Figure 4 </TD></TR></TBODY></TABLE> Travel Speed Too Slow (Figure 5)-Traveling too slow introduces too much heat into the weld, resulting in an excessively wide weld bead and poor penetration. On thinner material it may also cause burn through. <TABLE height=222 width=445 border=0><TBODY><TR vAlign=top><TD width=323 height=218></TD><TD width=112>Figure 5 </TD></TR></TBODY></TABLE> Wire Feed Speed/Amperage Too High (Figure 6)-Setting the wire feed speed or amperage too high (depending on what type of machine you're using) can cause poor arc starts, lead to an excessively wide weld bead, burn-through, excessive spatter, and poor penetration. <TABLE height=175 width=426 border=0><TBODY><TR vAlign=top><TD width=100></TD><TD width=100>Figure 6 </TD></TR></TBODY></TABLE> Wire Feed Speed/Amperage Too Low (Figure 7)-A narrow, oftentimes convex bead with poor tie-in at the toes of the weld marks insufficient amperage. <TABLE height=227 width=406 border=0><TBODY><TR vAlign=top><TD width=100></TD><TD width=100>Figure 7 </TD></TR></TBODY></TABLE> No Shielding Gas (Figure 8)-A lack of or inadequate shielding gas is easily identified by the porosity and pinholes in the face and interior of the weld. <TABLE width=381 border=0><TBODY><TR vAlign=top><TD width=323></TD><TD width=48>Figure 8 </TD></TR></TBODY></TABLE> (For more GMAW guidelines, download "Guidelines for Gas Metal Arc Welding" at http://millerwelds.com/resources/improving-your-skills/mig/.)
Goes without saying, but most newer machines (at least Millers and Hobarts) have a voltage/wire speed chart insode the cover. They're pretty accurate for most folks.
Except for 3 & 8 which I know don't look right, the rest of them I would think were just fine. I just don't have the trained eye yet. Good info. Thanks for posting!
When using a mig to weld say a corner weld on maybe a "L" type joint together do you push or pull it ? Does it matter ? On a longer run of weld do you weave it , like stick welding or just run straight ?
Push, pull, weave or straight pretty much depends on what you're trying to accomplish. Push results in a taller weld bead and less penetration. Pulling just the opposite. Weave is typically used when you need to put down more metal (wider bead).
Its a unimig 180. I think - haven't used it for a while. Its got settings 1 to 8 and a wire feed control, plus a timer that " helps " with plug welds.
my machine at work is a 1-10. all you need with mig is Voltage control, and wire speed. easy. just fiddle with it til you get a nice bead. thin metal will sound like bacon cooking when done right, thick metal (3/8, up) will make next to no noise when done right.
On my machine at work (Lincoln 255 Digital) I have digital voltage control as well as digital wire feed speed. However on my machine at my garage, (Lincoln Pro-Mig 140) Its A-B-C-D. I have no problem setting the machine at work, but at home I have a little confusion. Roughly what voltage does A-B-C-D represent? Or am I thinking this wrong?
its usually a percentage thing, so lets say your machine is 100 volts (not) a - 25V b - 50V c - 75V d - 100v much less refined, but keep in mind mig is constant Voltage, so you change your Amperage based on arc length.
I'm gonna beg to differ on this. Pulling a weld "stacks" more, creating a more convexed weld. Pushing creates a flatter, more spread bead. On top of that, pulling a weld will (usually) give you more penetration as you are spending time applying more volume of heat into the parent metal that was previously heated. Pushing a weld applies the heat to an area that is NOT heated, thus, less penetration (usually). Some people will tell you that you can't do one or the other, but that's a load of ****. There's times where you need to do a specific direction of travel. Not to mention that the general rule of thumb in many industries is that if you can push the weld, you should. It allows you to see what's ahead, and keep an eye on the puddle for things like arc length and penetration. If you can see the puddle clearly, you can see if you are maintaining consistency, and can adjust according to that sight. Also, some other things to consider.... MIG welding, like any other form of welding, when performed on plate of thickness over 1/4" should be welded UP if you are going vertical. This is something I see people doing incorrectly all the time, and when you're running down on thick plate, you're not getting much penetration before you're sagging anyhow, so it's best to spread what you get between the plates and tie them together. Use the "V" formation that would commonly be used with FCAW/SMAW vertical. (***FCAW and SMAW are NEVER under any cir***stance to be welded DOWN vertical!) Also of note, there are guides out there that say "This wire on this parent thickness should have these settings." Well, these are just guides. Theres more to it than that. Speed/Rate of travel is a BIG one. Some people like to weld slower and take their time. These people can create a great weld with a given IPM/Amperage. Then there's people who are confident that they can pace themselves quicker. Moving quicker means less time spent sinking heat in a specific spot, so you can weld with more volume of heat by turning the welder up to compensate. It's like hot rods. Some people like to get from point A to point B in their flathead powered rod at 75mph. Others like to get 115mph with their blown olds rockets. But either way, the trip and distance is the same. Shielding gas isn't really mentioned in the article either, but it plays a HUUUUUUUUUUUUUUUUGE role in welding. I'm not gonna go into specifics between mixtures of argon, C02, helium, etc., but if you are interested ask someone who sells gas at your local welding supply about the differences in shielding gas. You'll be amazed how much there is to know. Especially in relation to materials used.
you can weld downhand with stick. 6012, 6013, and another rod designed for shipbuilding which i forget the designation to. flux core is always pulled. never say never.
The general rule of thumb is vertical up. Just because you can doesn't mean you should. I *CAN* make a nice looking flux core weld going down if the settings are right... but I can promise there's gonna be a factor of slag inclusion in there.... Down will ALWAYS invite the opportunity for more slag inclusion... even with 6012, 6013, etc.
when done correctly there is no inclusion. the hard part is doing it right. but yes, i agree that the general rule is always up, but when doing Aluminum, when you are joining two pieces more than 1/8 difference in thickness, crank the heat and go down.
Depends on what's considered acceptable inclusion percentages. I've never heard of a shop that demands vertical down on ANYTHING when it's possible to vertical UP instead for that exact reason. When aluminum MIG welding go down? Or stick?
MIG, i weld dry bulk tanks, and when we're welding reinforcing channel to the skin, you have to go down or you'll burn through the skin. but all similar thickness joints are done uphand. when i say up the heat, we go down on 3/16 sheat to 3/8 channel at 34 volts.
You're right, I got it backwards. Not sure what I was thinking. As for speed, lots of times guys try to turn the amps down and run slower thinking they are putting less heat into the metal, but they end up taking forever to do the weld and the result is a larger heat affected zone. It usually works better to crank it up a bit and get the weld done quicker.
I couldn't agree more. haha I get made fun of at work when I'm MIG/FCAW'ing cause I crank that stuff WAAAAAAAY UP and move quick. I just don't have an issue with depositing where I want to, even when I'm moving fast.
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