Whenever MIG welding takes place, spatter most likely occurs. Resulting problems include spatter sticking to workpieces and equipment, the required cleanup, worker injuries and wasted material. Compounding the situation is spatter that eventually builds up on the weld nozzle and contact tip, causing them to have to be replaced.
Spatter is a symptom of MIG welding, but there are many options and technologies for reducing, or even eliminating, it.
On a basic level, spatter can be caused by incorrect welding settings, namely voltage being too low or amperage being too high. In MIG welding, amperage is determined by wire feed speed. To reduce spatter, the operator can lower the amperage by decreasing the wire feed speed or increasing the voltage.
But it’s not that simple.
“It would be as simple as reducing amperage and increasing voltage if every welding operator understood the rules,” says Matt Albright, senior product manager, The Lincoln Electric Co. “If X happens, change Y. But all of the combinations of the welding variables – the wire diameter, gas mixture, material – require different adjustments of wire feed speed, which affects amperage and voltage.”
To solve the actually complex process of achieving the right settings, welding equipment manufacturers have developed, over time, various ways to simplify how to set the welding equipment. A major advancement came with the development of inverter power sources with many waveforms, relieving the operator from having to make a majority of the welding decisions.
“If you just transition to inverter equipment, your welding will get better,” Albright says. “Based on the combination all your variables, the machine will behave in a way that optimizes the droplet transfer.”
On the pulse
Next, Albright says, it may make sense to transition from CV short arc or spray arc transfer to a pulsed waveform. “Now, the machine is actually controlling when and how fast the droplets leave, which leads to stability and less spatter. We can fine tune the combination of variables.”
Of the three metal transfer modes, the short arc and globular modes produce a great amount of spatter. Little spatter is associated with spray transfer. “With spray transfer, there is virtually no spatter, regardless of traditional CV or advanced inverter technology,” Albright says.
Short arc welding operates at low voltages. Molten metal transfers from the wire to the weld pool only when contact between the two is made, or at each short circuit. With globular transfer, the metal transfers across the arc in large droplets that drop into the weld pool. With spray transfer, metal drops from the wire in very small droplets, affording good arc stability.
Pulsed MIG welding helps eliminate the inconsistent delivery aspects associated with these modes. Pulsed is a non-contact transfer method between the wire and the weld pool. This means that at no time does the wire ever touch the pool.
It is a spatterless process that produces less heat input than spray or globular transfer modes. During the process, the current rises to a peak when the droplet is formed. Then, in the background current phase, the current is lowered to reduce the overall heat input. The process provides consistent feeding of similarly sized droplets into the weld pool.
Waveforms have improved with the introduction of the inverter power sources. Welding engineers are now able to control variables that affect the welding process, such as ramp rate, peak time, tailout and step off, in a precise manner. Lincoln’s advanced inverters, such as Power Wave, feature dozens of patented waveforms.
“There are 30 to 50 variables that our waveform engineers tune in order to get the droplets to transition the way that they want,” Albright says. “We have waveforms that are very specific for customers, such as automotive, heavy duty and pipe welding. It really starts to get into the science of welding.”
He does highlight the fact, however, that not every shop needs a high-end inverter.
“A lot of culture is involved with welding,” he explains. “We make some inverters built to operate the same way they did 20 years ago. Some customers like that and that’s the way their shop is set up. They have found a successful way to be productive with simpler equipment.”
Preferences don’t always come from the years of experience a welding shop may hold. They can also depend on what part of the country a shop is in and the schools their operators are coming from.
“Sometimes going from a simple machine to a very advanced machine isn’t the best approach,” Albright says. “It takes a couple of steps to get there.”
Need to know
Other factors that affect spatter control include the work angle. If an operator has an incorrect approach that is too steep or too low or he should be pulling when he is pushing, it can lead to instability.
“Our machines can see things happening and compensate for the operator’s actions,” Albright says. “The machine is only as good as its programming. It can’t accommodate for everything, but our machines certainly are adaptive, and they try to compensate for normal human imperfections.”
So while inverter technology certainly helps make an operator better, fundamental welding skills are necessary.
“The industry is always going to need people that know what they’re doing,” Albright says. “They have to understand how to set the machine and how to place the weld in a joint, which they learn in their classes and training. The equipment helps with training, simplifying setups and standardizing from work center to work center.”
Surface contaminants, such as rust, oil and paint, also affect spatter control. Although they don’t eliminate or prevent spatter, anti-spatter products can be used that prevent the spatter from sticking to the workpiece. Excessive amounts, however, can introduce other problems, such as porosity.
The shielding gas may also contribute to spatter. Rather than pure CO2, most people use a combination of 75 to 95 percent argon and 5 to 25 percent CO2 to reduce spatter. Lincoln tunes all of its waveforms to around 90/10 because it provides the most stable results, according to Albright. Beyond shielding gas, he goes on to say that welding wire quality is also a significant factor in spatter control.
“All wires are not created equal,” Albright says. “If you have a wire with a surface area that is changing throughout the spool, at certain wire feed speeds, it produces different amperages as the wire grows and shrinks in diameter, causing instability.”
All sorts of chemistry go into manufacturing the wire and then drawing and winding it in a specific way. This is to ensure that the wire is stable coming off the spool.
“At Lincoln, we consistently demonstrate the value of our wire even though it has premium price,” Albright says. “We tell customers time and again that you can use our fancy machines and waveforms, but if you use a subpar wire you’re not going to get the results we demonstrated to you. It’s always a combination of the machine, the machine setup and the wire.”
Save and spend
Albright notes one of the hardest things for customers to understand is that to make money they have to spend money. Spatter is a good example of that.
“Spatter gets all over the part and the shop floor,” he says. “Those parts have to be cleaned, which means investment in tools and consumables, such as grinders and discs. Spatter may also require investment in more PPE to protect the operators. Contact tips wear out faster and nozzles fill up faster. With robotic welding, spatter can reach the cables and burn holes in them.”
To make his point, Albright references the Pareto principle (also known as the 80/20 rule) that states that, for many events, roughly 80 percent of the effects come from 20 percent the causes.
“In general, most in the welding industry agree that the cost of consumables is less than 15 percent of the total cost of welding,” he says. “So, if 80 percent of your problems are the result of even 15 percent, even if you increase the cost of that 15 percent by 50 percent, that’s not that much to reduce the cost of that 80 percent by a significant amount.”
Looking at it another way, the decision to save 5 percent on 15 percent adds 10 percent to the 80 percent.
“We’ve been trying to change this thought process for years,” Albright concludes. “A consistent conversation we have with our customers is always to convince them to spend more and to prove to them that by spending more they will save more.”