Types of MIG welding processes
Welding power sources designed for industrial manufacturing typically offer several different welding processes, so how do you know which process will deliver the results you want?
Choosing the right process for your application needs and goals will help you enhance efficiency and productivity, as well as minimize weld defects and troubleshooting that hinder quality and throughput.
Learn more about the common welding processes used in manufacturing and how to choose the best process for the job.
CV MIG process
Constant voltage (CV) MIG is the most basic of the wire-fed processes. As the name implies, it provides a constant voltage output. There are three common transfer modes when using CV MIG:
- Short-circuit: This mode has low currents and voltages, making it good for thinner materials. It can also be used in all positions. However, it’s not a good choice for thicker base materials or joints where achieving penetration may be difficult. Spatter can also be an issue when using this mode, resulting in more time spent on weld cleanup.
- Spray: This mode has high currents and voltages, with a very stable open arc. It’s typically used on thicker materials in flat and horizontal positions. It’s not recommended to use this mode on thinner base materials or in applications where burn-through is a concern.
- Globular: This mode, which falls between short circuit and spray, results in an unstable welding process and is not recommended. Globular processes often occur inadvertently; they can happen when the voltage or current are too low in spray transfer mode or when voltage or current are too high in the short-circuit transfer mode.
Among the pulsed MIG technologies from Miller, this is the most standard pulsed arc. Accu-Pulse is an open-arc process similar to CV spray transfer MIG, but this process is stable throughout the entire wire speed range — avoiding the lack of fusion, poor bead profiles and spatter problems commonly seen with globular transfer. The output is pulsed to facilitate a ball transfer at the pulse wave’s peak voltage and current and a cooling effect during the voltage and current background. This process adapts to operator variations in stickout, which provides a 28% wider operating window that makes it easier for operators to produce high-quality welds. Considered the workhorse process for manufacturing welding, Accu-Pulse handles the widest variety of material thicknesses, making it a good all-purpose process. It can be used in all welding positions and with most solid or metal-cored wires.
Regulated Metal Deposition (RMD®) process
RMD is a modified short-circuit MIG process from Miller. Greater process control provides more operator control, a calmer weld puddle and less spatter compared to conventional CV short-circuit MIG. This process can be used on thinner-gauge material and is commonly used to fill gaps or weld open roots. RMD is typically used with solid wire and it can be run with most metals, but not with aluminum.
This pulsed MIG process features a tight but stable welding arc that’s designed for high speed. It provides the fastest travel speeds and is well suited for small fillet welds and gauge material thicknesses. It’s typically used with solid wire and can be run with most metals, but not with aluminum.
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Choosing a welding process
To determine the best fit, it’s important to consider what your operation welds most often and what your goals are. Here are four questions to help you decide which process is the right one for your manufacturing operation.
Q1: What is the material thickness?
The range of material thicknesses that are routinely welded in your operation is one of the most important factors in choosing a welding process.
The base material thickness governs how much heat can be put into the weld without burning through or how much heat needs to be placed into the joint to ensure acceptable penetration. Material up to 1/8-inch thick is well suited for CV MIG short circuit or RMD processes. On thin-gauge materials, short-circuit MIG is commonly used. However, RMD may allow a more controllable weld puddle, with less spatter and more reliable sidewall fusion. Thicker materials are well suited for Accu-Pulse or CV Spray.
In applications where the base material is up to 3/16-inch thick, the Versa-Pulse process can place small fillet welds quickly, providing high travel speeds that boost productivity.
Q2: What weld positions are used most often?
Can most welds in your operation be fixtured and positioned for flat welding in place, or do you need to do a lot of out-of-position welding?
A large weldment with dozens or hundreds of welds likely means that not all of the welds will be optimally positioned for in-position welding all the time. Doing both in-position and out-of-position welding requires a process that provides flexibility for both.
Compared to CV MIG spray, pulsed MIG (Accu-Pulse) allows more flexibility for welding out of position by keeping the weld puddle controllable for an operator to place vertical uphill welds on thicker materials.
Q3: What materials am I welding?
Whether you’re running aluminum, mild steel or stainless steel, certain processes are better suited for different materials.
Welding thick aluminum, for example, typically is best with pulsed MIG or CV MIG (in spray transfer mode). These processes provide better fusion to the root, and it can be difficult to get heat to the root when welding thick aluminum. Higher heat processes also create a more fluid weld puddle, allowing time for hydrogen to outgas from the weld to reduce porosity.
Stainless steel has other welding process options, including RMD, pulsed MIG or conventional short-circuit MIG. These processes have lower heat input and are good to minimize warping and burn-through. For thicker stainless steel, pulsed MIG or CV spray are commonly used.
Q4: What are the goals of my operation?
Is increasing productivity your top priority? Or is your biggest challenge the struggle to find and train new train new welders? The goals of your operation play a role in choosing the right welding process.
For example, pulsed MIG offers a more forgiving operating window, so welders of all skill levels can get good fusion into the root and sidewall to produce quality welds. Pulsed MIG also offers greatly reduced spatter levels, which reduces the amount of time spent on rework and cleanup.
The RMD process is great for thin materials and open roots and also produces less spatter — resulting in less time and money spent on clean up, in addition to greater productivity when compared to short-circuit MIG.
And because the Versa-Pulse process is designed for speed, you get more productivity from your welders on gauge material thicknesses.
The right process to optimize results
There are many variables that play a role in selecting the right welding process for the application. Considering the pros and cons of the main processes used for manufacturing and answering key questions about your operation can help you make the choice. Learn more about Miller welding power sources designed for manufacturing applications.