How to weld patch panels mig

This is an essential part of the process and you would not believe how often I see terrible welds over something as easy as pre-cleaning a weld surface. In most cases using a 60 grit Roloc disc will do the trick. Once finished, remove any residuals with wax and grease remover, paint thinner, or any other pure solvent. It is also essential to clean you welder tip and make sure you have sufficient gas flow to prevent porosity and impurities in the weld. If this step is done right, MIG welding thin body metal will be significantly easier.

This is usually where setup goes wrong. Most will set the welder to a very low voltage setting in effort to not distort a panel, but the weld penetration is very poor. Instead it is much better to set your welder up for small spot welds that are "hotter" than you would usually weld a bead. By spot welding the panel, you get very localized heat distribution and will prevent any warping.

If your welder is setup correctly, this will look very similar to a TIG weld. The goal is to travel around the panel with spot weld, stacking them up next to each other to fill the gaps. If done properly, there will be no porosity when grinding the weld flat. Here you can see a pre-made cab corner patch panel.

These t-slot clamps make easy work of aligning everything until tack welding is complete. For this step, I suggest only using a low grit roloc sanding disc on an air grinder. The reason for this is to prevent any additional heating of the panel that could cause distortion.

The less distortion, the less filler Bondo that will be needed which is better for long term durability of your finish. The following are some of the most common MIG wires used for auto body repair: ER : preferred by most welders because it is known for flowing better ; also has a lower melting point and is not super sensitive to weld cracking ER : the most commonly used aluminum filler alloy due to its high strength.

It is also easier to feed through the machine. So, to recap as far as wires and fillers go for car panels: You will likely be using a wire electrode in the ER4xxx or ER5xxx series. A smaller diameter wire has the most suitable diameter for auto bodywork. A popular aluminum filler metal that can work with a wide range of aluminum alloys is the ER, which can be found in the 0. Set the Voltage for MIG Welding Car Panels Aluminum has a thermal conductivity that is five times greater than that of carbon steel , which means that it will hold a lot more heat.

Examples of high energy modes of transfer include axial spray and pulsed metal spray: Axial Spray: a high voltage method of metal transfer that involves depositing wire electrodes as a stream of small molten droplets.

Speed is high enough to release several hundred droplets per second. This technique is best performed in either the flat or horizontal positions. Pulsed Metal Spray: this is a modified spray process in which the power source is actually able to fluctuate the voltage as much as times per second. The benefit of this technique is that it does a better job of maintaining the weld puddle to prevent burn-through. This method is not used as commonly as axial spray due to the associated learning curve.

Start with a Little Practice Finally, as hinted at in the above sections, you are certainly encouraged to do a few practice runs with your MIG welder before you do it for real. How to Prepare Car Panels for Welding When you are working with aluminum, cleaning the base metal is of absolute necessity. Use a solvent like acetone or a strong soap to clean the surface of the aluminum. Even water vapor on the surface of the metal will interfere with the welding process.

Use a stainless steel wire brush that you have dedicated exclusively for use with aluminum. Keep the aluminum covered overnight throughout the project. Make sure that the car panel is kept dry and at room temperature. Wire Diameter: The smaller, the better; shoot for the 0. Voltage: Keep the voltage at around volts.

Wire Feed Speed: Keep it high; you may need to experiment a little with this. Please enable JavaScript in your browser to complete this form. It looks like a slight arc. Now, anytime you apply the heat from welding, you are going to get a shrink as that weld cools.

When we weld one dot at a time, each and every dot is going to pull at the metal around it, from all directions, causing a shrink. Once you've added all those shrinks from all those weld dots together, along the entire weld seam, it adds up to a substantial amount of shrink such that what used to look like an arc is now more closely resembling a straight line. So given a weld seam like that, without any planishing to counteract the shrinking, you will see the panel pulling inward, as the crown at the weld is shrinking.

Looking at the panel as a whole, unchecked shrinking would appear as a pronounced valley, where the weld seam is shrinking and pulling the adjacent panels along for the ride. On the panel fitment, you will likely find that the sharp 90 degree corners on the patch will help to add a bit of distortion. As your welds shrink, a tight inside corner gets those effects from two different directions, where the shrinking effects will compound in the inside corner, normally as a pucker that is a bit challenging to remove.

On the corners a large sweeping radius helps to balance out the shrinking effects on either side of the weld, where the planishing efforts don't need to focus on puckers or deformity on one side only. As to addressing the welds: I have found that due to the manner in which each weld dot shrink pulls from ALL directions, you will have better luck in planishing to remove said shrinking effects if you can planish the weld dots while they are singular, sitting all by their lonesome.

And by stretching as you go, you help eliminate the panel being pulled into a valley on those long welds. As far as tacking the panel in place, FYI I normally would start the tacks at one end and work toward the other. I know many people will tell you to skip around to minimize heat buildup, and I have been one of those.

But if you tack one end and then move to the opposite end, you run a greater risk that one panel may have more material than the other due to misalignment. Once things get all tacked up, this results in a panel bulge on one side of the weld. So tacking from one end and working progressively to the other will help to eliminate this by being able to align the panels together as you go.

Now that the panel is tacked and weld dots are spaced about 2 or 3" , go back and planish each weld dot individually, to add a bit of stretch. At this point, I use a 3" cutoff wheel to grind down the dots to just above flush. This gets them out of the way for planishing the next sets of dots, and by leaving them just above flush, you can do the final cleanup with a roloc sander all at once.

By trying to grind things down to perfectly smooth after each, you run a greater risk of inadvertent sanding of the metal to the sides of the welds, which may thin and weaken the panel.

So I hold off on this until the end. This gives a much smaller contact area than most any other method, so you will have less heat buildup from the grinding process. Other grinding methods, such as using a flap disc, hide most of what you're doing, and generate too much heat. Here is a link showing the grinding method on a plug weld, again, sanding on a weld seam I would wait until the end. By overlapping, you will have less risk of missed spots or pin holes.

Continue with the weld, planish, grind, repeat until the seam is done. I typically weld from start to finish using weld dots only, none of the longer passes at the end, in order to keep everything consistent throughout the process. For the cutoff wheels, I spend the extra coin and get ones rated for stainless steel.

This makes them last longer and put less of that brown haze in the air that you see from the cheap HF or swap meet specials. By the time you figure out the cost of how quickly the cheap ones wear away, you haven't saved a thing. For the roloc sanding disc, the bulk of the welds are being removed by a cutoff wheel, we are only dressing what little remains of the weld and blending that into the parent metal.

This is easily accomplished using a 60 or 80 grit, that should be as coarse as you need to go.. There are a few different considerations in locating weld seams on low crown panels, such as the quarter panel.

For the most part one would put the weld up as high as possible, as most quarters have enough shape toward the top where the quarter slopes inward to help resist movement and distortion. It also puts the seam up where most if not all is better accessible for planishing. That is the normal scenario. In this case, one can be creative in making a dolly on a stick, say a piece of steel flat bar that would fit in the void, welded to a pipe to allow better reach. I've also employed the assistance of my nephew in remote cases where his youth permitted more of a contortionist approach over what my body refuses to do anymore.

This is also why it is important to planish those weld dots individually, and then grind them out of the way, front and back. This way two people can better work together on either side of a panel to planish out the welds, and find the correct weld dots in doing so. You also have the option of removing an outer wheelwell to better address an exterior panel that everyone will see, and then replace the wheelwell after you are satisfied with the metal bumping and finish work on the quarter.

Next, you can use features of the panel in your favor. Here is a lower replacement panel that I fabricated for the bottom of a 55 Chevy wagon lift gate, that has had no planishing performed, and looks to be one that will finish easily using only epoxy primer Other side Any imperfection are slight enough that epoxy primer will take care of them.

But as you can see, the panel where the weld travels through has a crown that protrudes outward in the horizontal plane, and inward in the vertical plane. So the shrinking forces tended to counteract each other, and the panel stayed exactly where it was.