Repair shops may not perform resistance spot welding now, but if they want to remain viable in the future, they better plan on acquiring that equipment and skill, according to Shawn Collins, collision industry specialist with AAA Auto Salvage in Rosemount, Minn.
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Collins presented an abbreviated version of his four-hour “Resistance Spot Welding” I-CAR class on Friday. Collins, who worked as a collision technician for 26 years and has taught about 30 I-CAR programs the past 15 years, boiled the course down into an essential 90-minute presentation.
Resistance spot welding, also known as squeeze-type resistance spot welding (STRSW), has made huge strides the last few years, thanks to welding equipment manufacturers.
“It is becoming more necessary due to changes in new cars,” Collins says. “More cars are being built that will require repairs using STRSW, which involves weld bonding with adhesives and spot welds. It’s impossible to do that with a MIG welder found in most shops. A MIG welder burns out the adhesive and defeats the purpose of the weld.”
He estimated that about 30 percent of collision repair shops in the United States have STRSW welders, largely due to their expense and initial limited use.
“They cost about $20,000 and some shops haven’t felt the need for them yet,” Collins says. “But more OEMs are recommending them for repairs on their vehicle platforms for safety and to reduce the weight of the steels used in the vehicle.”
OEMs can make their vehicles stronger and lighter by using heat-sensitive steels that will require repairs with STRSW. Adding adhesive to the weld allows OEMs to achieve the same rigidity as thicker steel that was traditionally repaired with MIG welds, he said. Since carmakers are being pressured to manufacture lighter and safer vehicles, this trend is not likely to reverse.
Unlike some new technology that adds cost and labor hours into the collision repairer’s job, there are some advantages to STRSW. The most obvious one is that shops will remain viable repair alternatives, as more cars require this technology.
Another advantage of STRSW is that it introduces very little heat into the work piece.
“You can touch the weld one second after welding it and it will be about 75 degrees compared to 580 degrees for a MIG weld,” Collins says. “A computer processor and inverter steps up the amperage and fuses the metal together very quickly without overheating the weld zone.”
There also are fewer consumables used because welders don’t need welding wire or shielding gas. They also don’t need to grind STRSW welds, which look like factory welds, he said. An STRSW weld can be performed much faster than a MIG weld, but more preparation is needed to clean and prepare the surface.
Collins also reviewed common mistakes shops make when investing in STRSW welding equipment.
“It takes more power than MIG welding and requires special wiring,” he says. “Shops are likely to need three phase power and they may need heavier gage wiring. Shops that don’t have 220 volt wiring can use equipment that runs on storage batteries and recharges on 110 volt power.”
