Spiral finned tubes for heat exchangers are manufactured by welding a metal strip, the subsequent cooling fins, along a usually thin-walled tube in a spiral pattern. The research project is currently developing a robot tool to optimize the manufacturing process. This should eliminate some non-ergonomic processes for employees. By using a flexible industrial robot, the spiral fin tube can be manufactured more individually by gradually varying the pitch of the spiral cooling fin along the course of the tube. This allows the properties of the heat exchanger to be improved for later use within a heating system.

Simplified set-up process

The new process should change three activities for employees: the set-up process, post-processing and maintenance. In the current set-up process, the metal strip is laboriously guided through a system of several deflection rollers. In future, the robot will automatically draw the strip into its tool and feed it into the welding process. To ensure that the process runs as efficiently as possible, a spiral finned tube is produced that is as long as possible and then sawn into shorter pieces. Laser welding is briefly interrupted at the sawing points that are not to be ribbed, but the metal strip continues to be wound up.

The employees then have to use pliers to manually cut through the metal strip at the sawing points and pull it off. This process is very unpleasant, especially with thicker metal strips. It also results in waste, which causes unnecessary losses, especially with high-quality alloys. This cutting process is now to be carried out by the robot tool shortly before welding. As a result, the metal strip is cut precisely to size and the sawing points remain free. Maintenance of the system is also simplified. At present, the accessibility of the system for maintenance purposes is not ideal. However, the industrial robot could rotate 180° and present the tool in a convenient maintenance position.

The advantages of high flexibility

The laser-welded spiral finned pipes are used in the heating industry, among others. Here, the exhaust gas heat is transferred to the heating or service water, sometimes in several sections. For this purpose, the spiral finned pipes are bent into a coil and inserted into the combustion chamber of the heating system. With the flexibility gained in adjusting the welding angle, the fin density on the pipe can be ideally optimized to meet the requirements of the respective heat transfer zone in the heating system.