Fraunhofer Chemnitz teaches robots to work more precisely

Chemnitz, 3 December 2023. Robots are regarded as tireless workhorses that can repeat the same few tasks with consistently high quality. In many cases, however, they work too imprecisely, for example when it comes to welding, forming and cutting sheet steel with high precision. Now, engineers in Saxony want to change this: In a new „application centre for web-guided robot processing“, the Fraunhofer Institute for Machine Tools and Forming Technology (IWU) in Chemnitz is using sensors, artificial intelligence and team principles to teach machine-learning workers how to master such precision tasks in automotive and aircraft construction and other industries.

 Spring-loaded robot arms and workpieces have so far prevented micrometre-precise work

Background of the problem: robots do not move 100 per cent exactly on the same paths - both their arms and the workpiece bounce a little, for example, and the laser seam or the cut is slightly off. This is why many companies continue to rely on proven computer-controlled machining centres, large presses and, last but not least, human experience when it comes to forming a sheet metal part for vehicles and aircraft or setting a laser weld seam in solar thermal modules with an accuracy of up to 50 micrometres, explained the IWU researchers. On the other hand, the purchase or operation of rolling mills and industrial machining centres is usually only worthwhile for the production of large quantities or if high prices can be achieved for the product.

Sensors, AI and duet work ensure greater precision

As a way out of this dilemma and in response to the growing shortage of skilled labour, the Fraunhofer engineers want to use special tools to teach robots precise movements. For example, they have developed a „levelling unit“ that ensures that the contact pressure and material removal remain constant when robots grind new forming tools. Until now, these tasks were usually carried out by experienced toolmakers, who would grind and finish the respective mould until the desired precision was achieved during forming.

One robot turns the component, the other welds

And so that robotic arms can finally master high-precision laser cutting, the Chemnitz-based company is equipping these systems with seam tracking sensors. And to achieve even complex 3D geometries accurately, they combine two robots: one rotates and turns the component, the other welds with its laser head.

Other IWU systems specialise in robot-assisted roll forming. In this process, a robot guides a pair of rollers alternately in both directions along the workpiece in several passes until, for example, a flange has been moulded into the desired shape, the engineers explain. Any deviations in geometry can be detected optically or via the reaction forces in the robot after each path movement.

Source: Oiger - Neues aus Wirtschaft und Forschung vom 03.12.2023