Kuhn Huard: "The secret of Valk Welding lies in the calibration"

Kuhn Huard is a renowned French company, and a member of the Kuhn group with a number of production facilities in France and the rest of the world. The branch in Châteaubriant produces ploughs, cultivators and precision saws, among other equipment. Due partly to a shortage of trained professional welders, the company is developing a Lean Manufacturing process, the aim being to robotise 100% of the welding work.

Many years' experience with robotised welding

Each of the group branches is fully autonomous when choosing its production processes and strategies, geared to the various machines to be produced. Various robots are deployed at the Châteaubriant branchsuch as: ABB and IGM. Valk Welding has supplied the last robot systems. "Besides aiming for a long cycle time of the welding robots, the required manual finishing work also needs to be drastically reduced. Faced with such stringent demands, Valk Welding scored better than other robot integrators in the end," explains Michel Le Grumulec, who is responsible for industrialisation

3-d model exact match in reality

"Thanks to the DTPS off-line programming software, Valk Welding offers a refined and extremely accurate method of programming," explains Damien Collin, head of production automation for new products. "It's the specific options of the Valk Welding robots that save us so much time:

1. When programming off-line, we can import the 3-D model as early as the design phase in order to assess the accessibility of each welded joint and to prepare the welding templates.
2. "The 3-D cell programmed by Valk Welding in DTPS matches the cell on the work floor exactly. Each program written using DTPS is therefore almost immediately usable on the robot system. Of course we always need to make a few adjustments before activating the robot, but the torch positions are already set and the tolerances are within a millimetre. This is extremely important, as it's not the first off-line solution used by the company. This function saves us a great deal of time when programmers need to use the software," adds programmer Mickael Rouesne.

Exchange of programs

According to Damien Collin, the general programming philosophy at Valk Welding differs strongly from other systems:
3. "In DTPS, the torch and the piece to be welded are associated, and the resultant axis movements do not affect the position-ing of the torch. In the other systems we used, it was the robot that generated the position of the torch, based on the position of its various axes. While this is a very subtle difference, it offers us considerable technological advantages. Thanks to this approach, we can very simply transfer programs from one welding robot system to another compatible robot system, even though they may have different configurations. On non-Valk Welding systems, we would have needed to completely reprogram them," explains the Damien Collin.

Direct continuation following collision

4. This also offers advantages in the event of the robot torch colliding with the work piece. "Such incidents cannot be completely prevented, but after calibration of the Valk Welding robots, we can continue to use the programs immediately, whereas the other systems would have required the programs to be rewritten because the TCP needed to be reset", Michel Le Grumulec continues.

A perfect digital twin

"Much of the success and the expertise of Valk Welding lies in the calibration according to a generally unique procedure applied as standard by Valk Welding to all welding robots, by integrating all mechanical elements in the control procedure when establishing the TCP." Over the years, the control procedure has been improved with automatic calibration procedures to be conducted by the client in order to establish the zero adjustment setting of each of the axes. For that purpose, the control procedure also features numerical calibration of each cell following commissioning on location. "This calibration forms the basis for re-use of the programs," Damien Collin concludes.
Kuhn Huard uses 20 welding robots by now. The most recent five have all come from Valk Welding, and a further three welding robot units are to be supplied at the end of this year. www.kuhn.fr