Welding, even automated welding, can be a messy process. Smoke, oil and dampening adhesive, resin, weld slag and spatter – it’s all part of the gig. Unfortunately, the mess can cause a robotic welder to misalign, and, in some cases, cause the proximity switch to fire on the wrong spot. This leads to situations where a robot either stops welding or lays down a bad weld, which then leads to downtime and increased amounts of scrap.
To combat slag and spatter on robotic welding equipment, the traditional method has been to use a hammer and chisel. It’s not uncommon for the weld line equipment to be damaged due to repeated impact. It’s a bit of a catch-22 because removing the slag and spatter is supposed to reduce downtime, but when the weld line equipment is damaged because of the frequent impact that occurs during the cleaning process, the opposite occurs.
Some manufacturers use conventional blasting equipment to clean their weld lines where they rely on an abrasive to help knock the slag off. This also creates a hazard to the equipment, and additionally leaves behind a lot of secondary waste.
Cold Jet, a company that developed an environmentally responsible method of cleaning up the mess, takes the hammer and chisel out of the equation with its “no contact” dry ice blasting technique. It serves an economical and effective way to remove slag and spatter buildup.
“This is a non-abrasive process,” says Giles Garrison, a manager at Cold Jet, “so you’re not going to damage the tooling. It can also provide a faster removal rate, and it’s better for the operator as opposed to using elbow grease to knock the stuff off. Instead, you can simply make a pass with the Cold Jet nozzle over that surface.”
The amount of time saved by using the dry ice blasting technique varies depending on air supply and application, but Garrison says it’s 80 percent faster than other cleaning processes, such as the hammer and chisel approach.
The science behind it
Three basic components make the dry ice technique work: kinetic energy, thermal shock and sublimation.
Cold Jet systems use high-density dry ice pellets and accelerates them out of the nozzle from 600 ft. to 1,200 ft. per sec. This creates an energy transfer when the pellets make contact with the contaminant, such as slag or spatter.
Dry ice has a temperature of -109 degrees F. The thermal shock created helps to release the bond the contaminant has on the surface of the equipment.
4And finally, dry ice particles sublimate upon impact, which means they turn from a solid to a gas, skipping the liquid state. This process expands the contaminant by 800 times, causing it to “pop off,” Garrison says.
The dry ice blasting machines are all equipped with wheels so they can be taken to the job site. They vary in size; for instance – the Aero C100, which is the most powerful machine Cold Jet produces, has a hopper that can hold 100 pounds of dry ice, whereas the smaller Xcel 6 has a smaller footprint and is designed to provide a reliable cleaning solution with minimal air requirements and has a hopper that will hold 13 lbs. of dry ice.
The dry ice Cold Jet uses is sourced from recycled CO2, often from places like ethanol plants, which emit a lot of CO2. The gas is captured, turned into liquid form and then into a solid, often in rice-sized pellets. Cold Jet also manufacturers dry ice pelletizers, including the PR350H, which produces up to 770 lbs. of high-quality dry ice pellets from stroke one.
“Almost all of our dry ice blasting customer base get their dry ice from an industrial gas company,” Garrison says. “Many customers have Cold Jet’s dry ice production equipment to make what is needed for their pellet-blasting units: high-density, 3-mm dry ice pellets.”
Cold Jet also makes a model that allows users to drop a large block of CO2 into a compartment where a shaver breaks it down before it is shot out of the Cold Jet nozzle. However, Garrison says pellets are most commonly used when cleaning welding equipment.
“Robotic weld line cleaning is one of the top applications,” Garrison says of Cold Jet products.
The dry ice blasting technology is quite versatile. Garrison notes the rate of acceleration of the dry ice pellets can be dialed back to where it can take the ink off a business card. It can also be turned up to higher velocities that can knock the asphalt off of roadwork equipment.
Along with robotic welding equipment, Cold Jet applications for welding include the weld table, transfer case, fixture, shuttle jig, trunnions, diamond plate and robot joint. Honda, Ford and Toyota use Cold Jet’s solution in their production lines.
Cold Jet released a case study on Maclellan Integrated Services, a customer that implemented the technology and estimates a cost savings of $2,956 per station per week. They reduced the labor hours related to cleaning from 7.2 to 0.5 per robot. The estimated annual savings amounted to $153,712. Remarkably, Maclellan’s return on investment was just 2.3 months.
“We are able to do two to three times the number of jobs and the outcome is better,” says Steve Foster, a Maclellan Integrated Services representative. “Also, we can meet the Kaizen ‘shared cost reduction’ now using Cold Jet and still make good margins on the job. Lastly, we keep finding more applications, which created more business for us with the same customer.”
Maclellan uses Cold Jet’s Aero 40FP dry ice cleaning system, which Garrison says is perfect for cleaning robotic welding equipment. When compared to using a hammer and chisel, the Aero 40FP reduced required labor from four workers to one at Maclellan.
Labor time was cut by up to 69 percent. Cleaning costs were reduced by up to 60 percent and Maclellan drastically reduced equipment damage. The only caveat is that photoeyes and proximity sensors shouldn’t be directly blasted.
Worker morale at Maclellan also improved because the Aero 40FP decreased labor intensity due to the fact that the unit is mobile and can be brought to the welding equipment, which is ergonomic and safer to use.
“We have operators ‘fighting’ over who gets to use it,” Garrison says.
To summarize, the key benefits to using the dry ice technology in robotic welding equipment include reduced scrap rates, reduced fixture repair, reduced replacement costs, minimized downtime, maximized tooling life and no secondary waste. Furthermore, the welder is not exposed to any dangerous chemicals or cleaning agents.