According to the Federal Ministry of Transport and the Federal Statistical Office, more than 70 percent of goods in Germany are transported by truck - and the trend is rising. The remaining 30 percent is transported by rail, rivers and canals. For a truck to bring its freight safely to its destination, its components must be perfectly joined together. Resistance projection welding is used here, which heats sheet metal with welding nuts, bolts and studs at certain points to such an extent that they fuse together at predetermined points and thus join inseparably. The components can be up to two meters long and have very different shapes. In order to securely join these parts together, the resistance projection welding system from Gatzsch Schweisstechnik requires a complete package of pneumatic drives, valve terminals, linear axes, air servo technology, proportional control valves and other high-performance components.

In Attendorn in the Sauerland region, Gatzsch Schweißtechnik develops and produces customized special welding systems, welding tools and devices as well as robot welding systems for the automotive and truck supply industry and also for other manufacturing industries.

Welding long truck parts as a whole

The universal resistance projection welding system from Gatzsch has a particularly long arm: the projection welding machine moves between and within the two work areas on a 7 × 2 meter long X/Y cross trolley, controlling the welding positions and welding the selected weld-on parts to the sheets piece by piece. "The system is highly flexible and can be used universally; it can be freely programmed for all tasks that can be welded with it," says Florian Tolle, Project Manager at Gatzsch Schweißtechnik. "The different sheet metal parts made of unalloyed and high-alloy material only have to be inserted and removed again - the rest is fully automatic."

This must be done with absolute quality assurance, as the truck components with the welded joints have to withstand hundreds of thousands of kilometers on the road. "Thanks to the wide working ranges, our resistance projection welding machine can also process very large workpieces quickly and accurately - with a perfect division of labor between man and machine," says Tolle.

SMC equips the Gatzsch resistance projection welding system with a comprehensive technology package - from pneumatic solutions for the precise welding head to coolant filtration. © SMC

To ensure that the resistance projection welding system can weld precisely in the long term, it requires a comprehensive combination of powerful pneumatic drives, accurate controls and other components such as grippers, clamping technology, coolers, welding cylinders and air servo technology through to air and coolant filtration. "A holistic concept for the entire system increases its efficiency and productivity because all components are optimally coordinated," emphasizes Maik Lohmeyer, Team Leader Sales at SMC. "Of course, the health of the employees working on the system always comes first. This is especially true when man and machine work together as they do in the Gatzsch resistance projection welding system." It must therefore be possible to switch off the compressed air supply for the pneumatic drives quickly. This requires particularly reliable safety valves. "At SMC, we are able to equip the entire joining cell with suitable and perfectly coordinated solutions," says Maik Lohmeyer. The experts at SMC have therefore designed easy-to-order and cost-effective technology packages for Gatzsch welding technology that contain everything that system manufacturers need - including the powerful VP series safety valves.

Optimum safety for the welding system

The VP safety vent valves are 3/2-way solenoid valves with safety limit switches. They can be used to reliably detect the position of the valve spool via a mechanical connection. "The safety vent valves are also very robust and have a service life of at least 10 million switching cycles," says Lohmeyer. If the system needs to be vented, the valve switches independently of the operating pressure due to the spring return of the valve spool. Lohmeyer continues: "The VP series can also be set up redundantly. With an additional safety vent valve, a system up to the highest safety category according to ISO13849 (category 4) can be implemented. If one of the valves fails, the other vents the system pressure." The redundant VP safety valve is also available with a soft start function. This means that the pressure is slowly increased when the system is switched back on.