Welding of solar thermal modules with fiber laser and line scanner

The customer manufactures modules for systems that use solar thermal energy to generate heat for heating systems, swimming pools and other systems that require heating. For the production of the solar modules, the customer commissioned Lasaco's experts to design a robotic system for automated laser welding. A decisive factor in the choice of this welding process is the high precision and reproducibility of the welding results achieved by uniformly operating industrial robots. In the field of solar technology, not only precise but also durable weld seams are required, which hold without problems under all weather conditions.

In contrast to solar systems with photovoltaics, a liquid carrier medium circulates in modules for solar thermal energy, which is why the system must be absolutely leak-proof. Manufacturers of solar systems usually give their end customers a long warranty period, which further emphasizes the need for perfect welding work. To obtain the required precision and quality in laser welding, Lasaco installed a KR 30 industrial robot from Kuka, which operates on a rotary axis with counter bearing in single-station mode and precise fiber laser. Perfect and safe positioning of the components was an important element in the design of the industrial robot. Special importance is also attached to a special mirror system with line scanner in order to always focus the fiber laser exactly on the right area of the components.

Construction of a special welding device for the fiber laser

Our fixture construction department had to solve the problem that perfect positioning of the solar modules was only possible with a fixture specially developed for this Kuka industrial robot. By means of the pneumatic system we developed ourselves, the modules are positioned with pinpoint accuracy and fixed in such a way that they cannot shift during the machining process with the fiber laser. Without perfect positioning, reliable laser welding is not possible. To ensure safe operation under all operating conditions, the welding device was also equipped with various safety features. For example, two-hand operation is required for operating the pneumatic clamping device of the industrial robot in order to rule out the possibility of accidental finger entrapment from the outset.

Technology: Pulsed CW fiber laser with precise line scanner

The components of the solar modules are welded with a pulsed CW fiber laser after exact positioning by the Kuka industrial robot. The use of the line scanner with high-performance mirror optics not only enables absolutely tight welding of the components, but also creates visually appealing weld seams. For systems that are usually installed in building facades or on roofs, optics naturally play a major role with the end customer. The most important advantage of laser welding with a scanned beam in this configuration is the spot welding of the housing with the simultaneous possibility of reliably fusing corners. To improve operations, Lasaco also installed a powerful fume extraction system attached to the manipulator arm of the Kuka industrial robot. This allows welding gases and fumes to be reliably extracted from the work area and conducted outside.

Kuka industrial robot with fiber laser for reliable laser welding

With its KRC4 controller for precise positioning of the welding processes, the Kuka KR30 robot is ideally suited for series production of solar modules in the required quality. Particularly in the case of solar thermal modules, the absolute tightness and durability of the weld seams is crucial for the smooth operation of systems for heat generation. In conjunction with the pneumatic clamping device specially designed for this customer, process reliability is guaranteed. This means that the process sequence is not only safe and reliable for the operating personnel, but that the laser welding results are always of a consistently high quality. The simplified handling also increases the productivity of the production line, as throughput times can be significantly reduced compared to manual production and output can be increased.

Highlights of the project at a glance:

  • CW fiber laser with 1 kW power and single mode operation

  • Line scanner with mirror optics for precise guidance of weld seams

  • Precise positioning of components by pneumatic clamping device

  • Implemented with Kuka KR 30 industrial robot with KRC4 control unit

  • Fully automated single-station operation with rotary axis and counter bearing

Project gallery: Laser welding of solar modules with fiber laser and line scanner based on a Kuka industrial robot