Beginner Tips and Tricks
A practical guide for new welders covering common MIG welding issues and simple adjustments that can dramatically improve weld quality and consistency.
Troubleshoot Your Way to Better MIG Welds
Congratulations! After much deliberation (maybe too much), you’ve finally invested in that new welder you’d been thinking about for a while, and you’ve taken some of your first steps into the world of welding. At the very least, you’ve probably set up the machine, reviewed the manual and made a few sparks. The only thing left for you to do is invest some time in learning a bit of theory and technique, and develop an understanding of some typical weld problems and ways to respond to them.
The image below illustrates several different types of weld problems. The solutions are usually just a matter of a few simple adjustments, but they’re not always that obvious. This column looks at some typical weld issues and offers suggestion about how to fix them.
Once you’ve turned on your machine, but before you start welding, take a minute to just listen. What you hear can tell you plenty. The rule of thumb is that when a machine is adjusted properly, it sounds like bacon frying in a pan. You should hear a smooth, consistent sizzle. The weld on the far left in the image below is smooth, straight, even and consistent in length and width (A). It’s a good example of what your MIG welds should look like.
Wire Feed Speed Too Low
Wire feed speed controls amperage. Think of amperage as heat: the higher the amperage, the more heat in the puddle. If your wire feed speed is too low, it will not generate enough heat to melt the amount of filler wire being fed into the puddle. You can see from the illustration that the molten puddle is not fused very efficiently into the base metal. Instead, it just lays on top of it. The result may be a decent-looking weld, but there’s little or no fusion. This is a potentially dangerous issue with MIG welding.
THE FIX: At the beginning of your weld, increase your wire feed speed slowly – in small increments, without adjusting the voltage – but also make sure your arc length remains stable and consistent. Turn the wire feed speed up until the metal begins to melt smoothly and that satisfying sound of frying bacon is ringing in your ears.
Wire Feed Speed Too High
When the wire feed speed is too high, the puddle becomes too fluid and there’s simply more molten metal than what can properly fuse into the base metal. This makes for wide beads that are usually flat, and sometimes even concave. It makes the weld harder to control, and believe it or not, can even lead to problems with insufficient fusion.
THE FIX: Reduce the feed speed in small increments until you get the desired results. Depending on the material thickness, you can also add voltage to help smooth the process.
Electrode Stick-Out
Electrical stick-out is very important. Improper stick-out can greatly reduce the integrity of a weld. When the electrical stick-out is too short, it does not allow space for the arc to work properly, heat the base metal properly or melt the filler properly. When the stick-out is too long, the amperage decreases and therefore the heat decreases, which results in a cold weld. This is usually characterized by a tall narrow weld that is not fused well on the edges.
THE FIX: Try positioning your head so you can see the weld better. Following visual cues is very important in the welding process. Make yourself more comfortable, brace your body and use your free arm to steady the arm with the gun in it. Before you actually weld, try a few dry runs by moving the gun across the weld joint without pulling the trigger.
Travel Speeds
A good MIG weld requires you to keep the wire on the leading edge of the puddle. Some think slowing down the travel speed will increase penetration, but it doesn’t. If your travel speed is too slow, you’ll produce a lot of melted wire with little fusion into the base metal. A travel speed that’s too fast doesn’t allow the puddle time to do its job. A weld puddle can very quickly become to cold by traveling too fast.
THE FIX: As mentioned earlier, paying attention to the visual cues can be helpful. Watch the puddle. Keep the wire on the leading edge of the puddle and move as fast as you can while keeping the puddle “round.”
Gun Angles
We generally work with two gun angles, and consistency with these two angles is important to the making of quality welds. Work angle is the angle of the gun, which splits the weld between the two pieces of material. We usually always want the same amount of weld on each piece unless welding thicker metal to thin metal. Travel angle is the angle at which we hold the gun when pointing in the direction of the weld.
The gun angle is important in that it directs the weld where it needs to go and ensures a quality weld when the job is complete. You can adjust angles according to what the puddle says.
Inadequate Gas Coverage
Lack of gas coverage causes holes in the weld, a phenomenon better known as porosity. This destroys the quality of the weld and makes a weld very weak. The most common causes of inadequate gas coverage are a draft or breeze, a pinched gas line, a loose fitting, insufficient gas flow or even too much spatter in the nozzle of the gun.
THE FIX: Block any drafts in the work area. Check your system for leaks, clean the nozzle, make sure the gun is seated all the way into the machine, and check the hose for holes.
Some Additional Techniques
Whipping the gun is a very helpful technique when welding the thinner materials that we frequently encounter in our smaller shops. This technique can lead to fusion issues on thicker materials, but it’s very helpful when used properly on materials in the 3/16” range or thinner. I use it almost every time I pick up my MIG welder in my garage.
Whipping is basically a heat control technique used to flatten the weld. The same technique is used with a 6010 stick-welding electrode. It’s especially helpful with any sort of automotive welding. It creates less heat input, which results in less distortion and produces a better-looking weld. Whipping will also save a lot of grinding time in the finishing process because the welds are much flatter. In fact, once you master this technique, your welds will look so good you may not need to do any grinding at all.
Here’s how it works. As you make your way along the weld, quickly whip your gun/wire forward, just past the front edge of the puddle and then back onto the puddle. The forward motion pulls heat out of the puddle to flatten it, and then the backward action builds the puddle up to fill the weld to proper height. This action pulls some of the molten metal out of the center height of the weld and pushes it to the sides, which facilitates wetting the puddle into the base metal.
Be sure not to whip too far off the puddle. This can impede fusion on thick materials, but it isn’t a big concern on the thinner materials. After some practice, this technique can be very effective and create quality welds with an excellent appearance that requires very little finishing, if any.
Triggering is another technique that can be especially helpful when welding materials in the 16-gauge range and thinner. This technique is also commonly referred to as “the poor man’s pulse.” When welding automotive sheet metal, triggering is basically a series of overlapping tack welds.
Pull the trigger and make a nice, round tack weld. Then move the gun forward about half the distance of the previous tack and pull the trigger again. Repeat this process all the way across the weld joint.
Triggering can produce flat, smooth welds on very thin and temperamental sheet metal. It can also be very helpful when the material fit-up is less than perfect – which is often the case. The larger MIG welders have pulse features that perform this technique automatically, without the operator having to pull and release the trigger. In addition, some machines have a “stitch welding” feature, which is similar to triggering.
As with any welding technique, you can master whipping and triggering with a little practice. When executed properly, both can be very effective on thinner materials.
When you’re just getting started in welding, there are many factors to consider. The pitfalls and techniques described here are some of the most common. Just remember that welding is all about variables and keeping them in the range necessary to make a good, strong weld.
Welding is also all about having fun. So get out to the garage with that new welder and build something.