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Fully automated boiler welding

Premium ‘Made in Austria’ quality and a strong innovative spirit have been the hallmarks of the heating specialist Windhager for over a century. Against this backdrop, the Salzburg-based firm recently invested in one of the most innovative boiler welding systems in Europe. A total of 13 robots from KUKA ensure maximum productivity and flexibility in the fully automated welding line system provided by ism-technic.

With Windhager, what you get is what you see

The trend towards prioritizing long-term value over short-term gains is gaining visible traction, particularly in the heating sector. Economical and sustainability factors are now among the most important criteria when purchasing a heating. ‘We got on board with the biomass heating trend early on and started to specialise in the production of environmentally friendly log heaters, wood chip heaters and efficient pellet heaters,’ explains Stefan Gubi, CEO of Windhager Zentralheizung GmbH. 

Today, the family-owned company based in Seekirchen with around 650 employees is one of the leading manufacturers of boilers for renewable energies. In order to establish an additional foothold, the traditional Salzburg-based company is currently building a 27,000 m2 production and development centre for heat pumps in Pinsdorf near Gmunden (Upper Austria). Starting in 2024, up to 20,000 heat pumps will be produced at the site on an annual basis in partnership with heat pump specialist M-Tec. But that wasn’t quite enough for the heating specialist. Innovative production technologies for boiler production are constantly being invested in at the production plant in Zaisberg/Seekirchen in an approach based on strong vertical integration. ‘With Windhager, what you get is what you see. Hence the demands we place on production to manufacture as much as possible in-house,’ assures the CEO.

‘In addition to an extensive range of machinery in sheet metal production for laser cutting, punching and bending, we also have a powder coating system. We take care of barrel finishing, vibratory finishing and surface grinding all the way to electrical production and final assembly in house,’ adds Patrick Heitzinger, Head of Production at Windhager.

With one of Europe's most innovative boiler production lines, Windhager has successfully automated boiler welding, including tack-welding and parts logistics, across the board.

Increasing capacity with welding automation

In order to meet the strictest criteria in terms of reliability, safety and the service life of boilers, as might be expected, boiler welding is also one of the traditional Salzburg-based firm's core competencies. However, due to the major hike in the number of units to be produced in recent years, capacity limits are increasingly being pushed. 

Fully automated boiler welding using KUKA technologies.

‘In order to cope with these volume increases while continuing to meet the ever-stricter quality requirements and, above all, to counteract the acute shortage of skilled workers, increasing the degree of automation in welding production is inevitable,’ emphasises Gubi. Windhager therefore decided to replace the existing, outdated robot welding systems with a fully automated, state-of-the-art welding line system.

BioWIN, the Windhager boiler family with the most units is automatically tack-welded in the two tack-welding cells.

The main benefit to the new welding line system is increased capacity and productivity. A planned production increase up to 40 percent is therefore more than achievable.

Stefan Gubi, CEO of Windhager

One of the most innovative boiler welding line systems in Europe


ism-technic GmbH was commissioned to come up with the automation solution. The KUKA System Partner from Münchendorf, Lower Austria, specialises in tailor-made, turnkey robot cells and complete production systems for welding and cutting, including material handling. ‘However, the project was not without its own set of highly complex issues. Luckily, as a KUKA System Partner, we have an extensive product portfolio at our disposal, which has enabled us to automate not only the welding process, but also the loading and unloading of the individual robot cells as well as the entirety of parts logistics,’ reports Andreas Stremitzer, CEO of ism-technic. He takes great pride in what has been achieved: ‘Being able to compete with such reputable vendors of automation solutions has felt like winning gold at the Olympics. I truly believe that here in Zaisberg we have created one of the most innovative fully automated boiler welding line systems in close partnership with KUKA and Windhager, the likes of which remain unparalleled in Europe.’

Assemblies which are subsequently required in the tack-welding station are welded in the pre-welding station of the tack-welding cell.

Since the end of last year, the new production line has been in operation with two identical tack-welding cells, six identical welding cells and a high-bay warehouse. ‘The solution from ism has made it possible to fully automate the welding of our boilers with optimum process reliability, from tack-welding to transport to the reworking stations, where employees still apply the final welds and check the boilers for leaks,’ says Heitzinger. The concept is designed to allow all of Windhager's 19 boiler types at present to be welded in each of the six welding cells. ‘With this approach, we can flexibly adapt production to the constantly changing demand for individual boilers. In addition, any malfunctions that occur in a cell no longer result in production bottlenecks,’ the Head of Production happily declares.

Thanks to the new production line system from ism, the welding of our boilers, from tack-welding to transport to the reworking stations, has been fully automated across the board with maximum process reliability.

Patrick Heitzinger, Head of Production at Windhager

High productivity with automated tack-welding

Currently, only the two boiler sizes from the Windhager BioWIN range with the highest number of units are automatically tack-welded in the two tack-welding cells. The other boiler types, for which automation of the tack-welding process would not be suitable due to the many different variants, are still manually tack-welded in their own tack-welding fixtures and fed into the plant via a roller conveyor system for final welding and stored in the high-bay warehouse. 

ism-technic implemented the fully automated welding line system with KUKA technologies.

‘By making this switch for the BioWIN boiler, we were able to increase tack-welding productivity by around 50 percent,’ claims Heitzinger. One tack-welding cell is equipped with two KUKA welding robots KR CYBERTECH ARC – one for welding pre-assemblies and one for tack-welding the entire boiler. The individual sheet metal parts required for this process are first placed into component carrier pallets by an employee and fed into the line via a roller conveyor belt. Before they are then stored in 16 designated drawers of the shelving system, a camera system checks whether the parts have been inserted correctly into the pallet. One KUKA handling robot KR QUANTEC is provided for each tack-welding cell, which removes the required components from the shelving system and supplies one of the two robot stations in the cell with material, depending on the order.

A handling robot removes the components required in the tack-welding cell from the shelving system.

‘A BioWIN boiler to be tack-welded consists of a total of 18 components, which are inserted into the tack-welding station either as individual sheet metal parts or as a sheet metal assembly that has previously been welded in the pre-welding station,’ the Head of Production explains in detail. Andreas Stremitzer continues: ‘Thanks to an automatic changing system with six different grippers, the handling robot loads the cell with full process reliability every time. Even small devices that are required in the pre-welding station are automatically positioned on the welding table without the need for an employee to lift a finger.’

A KUKA heavy-duty robot is responsible for loading and unloading the six welding cells.

In order to be able to insert the parts optimally and to ensure that the robot is always in the ideal position for tack-welding, the tack-welding station also features a KP2-HV HW two-axis positioner from KUKA. ‘An automatic wear part replacement system, automatic TCP correction as well as mechanical torch cleaning mean there’s no need for external intervention, ensuring fully autonomous tack welding,’ adds the CEO of ism. The handling robot KR QUANTEC removes the tack-welded boiler from the cell and transfers it to a transfer station, from where it is taken by a storage and retrieval machine and stored in the high-bay warehouse for subsequent final welding. ‘The cells are designed to allow a BioWIN boiler to be tack welded every 30 minutes,’ Heitzinger emphasizes.

As a KUKA System Partner, we have an extensive product portfolio at our disposal, which has enabled us to automate not only the welding process, but also the loading and unloading of the individual robot cells as well as the entirety of parts logistics.

Andreas Stremitzer, CEO of ism-technic

The welding section of the production line consists of a total of six identical welding cells, all of which are loaded and unloaded by a KUKA handling robot KR QUANTEC. At the same time, the KUKA heavy-duty robot KR 600 FORTEC mounted on a ground track equips the selected welding cell with the corresponding fixture. ‘In order to ensure continuous traceability in our production, a QR code is affixed to each boiler and recorded in a database. This ensures it is always possible to check when, in which cell and with which welding parameters the boiler was welded,’ Heitzinger explains in more detail.

The handling robot precisely positions the boiler to be welded in the clamped fixture.

The handling robot then brings the boiler to the selected cell and precisely positions it in the clamped fixture. In order to ensure the robot consistently has the optimal welding position, the cells are equipped with KP2-HV HW two-axis positioner from KUKA. The welding cells also feature an automatic swan neck replacement system. ‘Due to the use of different torch lengths, there are hardly any restrictions when it comes to boiler accessibility. We are now in a position to automatically weld far more seams than before,’ claims the Head of Production. ‘Each boiler is measured by a laser sensor before welding, compared with the programmed reference boiler and aligned in the correct position in the event of deviations,’ remarks Stremitzer.

In addition, as in the tacking cells, an automatic wear part change system like the one found in the tack-welding cells automatically changes the contact tip in good time on the basis of empirically determined values. Finally, if a fully welded boiler is called up at the push of a button for reworking and leak testing, it is automatically transported overhead on a conveyor line to the reworking station. ‘The amount of re-welding fell massively,’ claims Heitzinger, who notes: ‘The new welding automation has also been an enormous relief for employees.’

In order to ensure the robot consistently has the optimal welding position, the cells are equipped with a two-axis positioner from KUKA.
State-of-the-art welding automation achieved in partnership: Andreas Stremitzer (ism-technic) and Patrick Heitzinger (Windhager).


To Windhager CEO Stefan Gubi, the main advantage to the new welding line system is the increased capacity and productivity. ‘A planned production increase up to 40 percent is more than achievable with the new production line. It also allows us to respond to market changes with a great deal of flexibility and speed and, if necessary, run unmanned night shifts.’


ism CEO Andreas Stremitzer notes that he always appreciates being able to rely on a strong partner like KUKA for large-scale projects like this one: ‘As a system integrator at our size, achieving such a complex automation solution would be extremely difficult without the support of a strong robotics partner like KUKA.’

Stefan Gubi also views partnership on equal footing as crucial to success: ‘A consistently customer-centric approach is one of the trademarks of Windhager. We also expect our partners to follow suit. The way in which our wishes, requirements and also problems were handled was exemplary. I take my hat off to partners like ism and KUKA and look forward to a successful future together.’

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