Bodywork company: What is Spot Welding?

Brian Wasson: One of the most common challenges our I-CAR instructors face at training events is variation in terminology. The most common variance is plug welding and STRSW or spot welding. Technically speaking, they are not the same, but many use these two terms as if they were the same.

MIG plug welding or plug welding is a process in which two or more mating flanges are attached by filling punched or drilled holes with molten filler metal using welding equipment. the gas and metal arc (GMAW). This process is considered standard practice among auto body repairers. However, in original equipment (OE) repair information, this process has become less common. Producing quality plug welds requires fine technique and skill to achieve the right amount of penetration without overheating the material. In our training and certification programs, our instructors provide one-on-one coaching to improve these techniques and skills.

Although STRSW involves attaching two or more mating flanges, it does not require holes punched or drilled in the mating flanges. In this process, two electrodes squeeze the mating flange at high pressure and apply high amperage to create a nugget of solder. The equipment used for this process is very specific and usually requires a specific (three-phase) infrastructure to operate.

BSB: Why is STRSW becoming a popular recommendation from car manufacturers?

pc: With each new model year, original equipment manufacturers (OEMs) strive to meet consumer demands for more advanced features and higher safety ratings while trying to achieve better fuel economy. Every advanced feature and additional safety system adds weight to a vehicle, which affects fuel economy. One method used by OEMs to reduce overall vehicle weight is to use higher strength steels, as they can match their road and crash performance with these lighter steels.

There are many types of steel available to automotive engineers, each with their own unique characteristics. These steels have one thing in common: heat affects their strength. Since STRSW allows steel parts to be fastened with minimal part heating, it is an ideal choice for OEMs to use in the manufacturing process. Traditional methods such as GMAW (MAG welding) achieve panel attachment, but the process requires the steel parts to get very hot, which can change their characteristics and affect the vehicle’s predicted crash performance.

BSB: What precautions are necessary when spot welding around ADAS components?

pc: OEMs will provide guidance on welding precautions during the repair process. These precautions are usually found in the general repair information of the repair manual. In my experience, precautions specific to Advanced Driver Assistance System (ADAS) components are similar to any electronic system or module, involving the removal of modules, sensors, and wiring harnesses from the vehicle. In some cases, the component is located several feet from the repair area and requires additional disassembly. It is recommended to develop a repair plan early in the repair process so that these necessary actions can be identified immediately.

The reason OEMs provide these specific precautions is that a by-product of any welding process is the creation of a magnetic field, which can introduce voltage into vehicle electronic systems and damage them if precautions are not taken. not taken. Since STRSW is a high current process, this magnetic field can be very large. You may have noticed that welding machine cables move or jump when the machine is triggered and nearby metal objects become magnetized, which is physical evidence of the presence of this magnetic field.

BSB: Is there a particular metal recommended for spot welding?

pc: As a general rule, any hot stamped (or boron) alloy steel requires STRSW; however, STRSW can be applied to any steel. It is common for exterior spares to be made of low tensile steel, and these are welded to the interior panel, which is high tensile steel.

BSB: Where is welding technology today?

pc: We’re in luck these days with STRSW technology. A common feature of modern welding equipment is their ability to automatically adjust machine settings to achieve a quality spot weld and preserve its characteristics. However, we encourage repairers to learn the manual method, as some OEMs will require specific clamp pressure, hold time and amperage in specific areas of the vehicle. When necessary, these “smart” welders must be put into manual mode to properly apply the weld.

BSB: How important is training?

pc: STRSW is procedure-based, and like any procedure, if a step is skipped or not performed correctly, it will affect the outcome. Our hands-on training program focuses on performing the procedures and provides verification of specific steps that equip the repairer with the knowledge and skills necessary when performing the STRSW. We do our in-shop training using the same equipment the repairman uses for collision repair. Plus, we help repairers understand shunts and material coatings to make successful welds. It’s common (and expected) to run into app issues, and our instructors have been trained on how to identify and fix issues.

I would also recommend that repairers get specific training on their equipment because having the right tool is one thing but knowing how to use the tool correctly is everything. All of the equipment manufacturers that I know of have a training program for their equipment, and in some cases they partner with I-CAR to provide this training. Ask your equipment supplier what training programs are available.

BSB: Why is it important to follow OEM welding guidelines?

pc: The only way to ensure that “as built” crash performance is maintained is to follow the OEM repair information. A common problem for repairers with OEM repair information is interpreting the information, and in my experience the best way to overcome this challenge is to receive training and, most importantly, implement the lessons learned into their daily operations.

BSB: How critical is maintenance?

pc: All of the equipment in every collision repair shop is a tool, and production environments use these tools on a regular basis. These tools require regular maintenance not only to keep them in working order, but also to prolong their lifespan. Check the owner’s manual for maintenance needs, and if you can’t find the manual that came with the equipment, search online, as most equipment manufacturers make the owner’s manual available through their website.

There are two frequently missed regular maintenance items that we encounter at our training events. The first is the condition of the electrode tips, which flatten out over time and need to be repaired or replaced. These tips are considered consumables and should wear out over time. Another is the condition of the equipment’s internal coolant; this coolant should be replaced regularly and if maintained in good condition will prolong the life of the equipment.