Building with industrially prefabricated system elements made of steel and concrete is a business segment of Goldbeck, a company with over 7500 employees and 70 international locations, which is primarily active in hall and parking garage construction. The load-bearing framework is formed by differently shaped and dimensioned steel girders with all their connections, from the top plate to the web plates. Each of these components can have any number of special features - a conventional automated welding line was therefore not practical for Goldbeck. This is because each unique component requires individual programming: parameters such as material, exact dimensions, elements to be welded and weld seam position and design must be programmed offline (using CAD data sets). This means that a welding robot can only really exploit its economic advantages in the long term once a certain minimum batch size has been reached.

Automatically welding batch size 1 profitably

The IRPS laser (visible by the red line) scans the real component with its position and generates a point cloud, which is converted into a 3D model.

© Exner

Goldbeck had launched various research projects to find a solution for batch size 1 welding. However, the results were all rather sobering. In 2018, the company then heard about the 'Instant Robot Programming System' (IRPS) from Instantpro in the Netherlands for the first time. This company made the - at the time bold - claim that IRPS could even weld individual parts cost-effectively and fully automatically.

"The contact with Exner Ingenieurstechnik as project partner and Instantpro as manufacturer of IRPS came about via Kuka Industries, whose systems we were already using in other areas," explains Christian Schneider, Project Manager Steel Construction Production at Goldbeck. "When we were informed that IRPS would be able to recognize workpieces itself and generate welding programs from them, it sounded very futuristic, if only because of the many variants that the system was supposed to take into account. So we got in touch and went to see a test system at Exner in Holland."
The patented system can automatically weld different product families in steel construction with any dimensions and in any combination. Components known to the system no longer need to be checked, and each new material or profile is stored in the system just once, together with the optimum welding parameters. After that, everything is automatic.

How does this work in detail?

Put simply, the workpiece is placed loosely on a fixture or - if necessary - fixed in place, depending on the component and size. The positioning is irrelevant, as the robot recognizes the real dimensions. To take measurements, it receives the order by clicking on a touchscreen. It then moves over the component and reads its dimensions and position using a laser scanner. This laser scanner is permanently mounted on a linear axis or directly on the robot. As it moves over the component, a precise 3D model of the component itself is created, eliminating the need for exact zero-point fixing and searching for seams.
The result is a point cloud. The IRPS basic software uses this to recognize a component shape stored in the database - for example a double-T beam - and uses algorithmic programs to create a finished robot welding and movement program. At the same time, the optometric 3D scanner image is generated and displayed on the touchscreen.
This 3D model of the component can be rotated in space on the monitor, similar to CAD models. The display is used to check and possibly change, for example, welding seams, welding parameters or torch position.

The IRPS software recognizes the double T-beam (grey) and the components to be welded to it (orange).

© Exner

The IRPS software also functions as a higher-level controller for the welding robot. It controls the process sequence, creates the movement program for the scanning process, generates a model of the component from the 3D point cloud obtained after the scan and writes finished robot welding and movement programs. The software is linked to the IRPS hardware via a license. It controls a 6-axis robot, an additional linear axis and a scanner. Further additional axes, robots or scanners are optional.
Once the scan has recognized the component and placed the weld seams graphically, the worker releases the complete welding process with a single click on the touchscreen. Detailed robot and welding knowledge is not required.