34 n ROBOTICS AND AUTOMATED MANUFACTURING February 2025 www.drivesncontrols.com Robots solve tricky issue on hydraulic valve assembly line The Swiss hydraulics specialist ArgoHytos has commissioned an automated cell for producing electromagnetic valves that uses Scara robots to perform all of the handling operations – the most challenging of which is the screwing and unscrewing of valves at an end-of-line test station. The valve production line, which was previously operated by hand, is located at a factory in the Czech Republic. Argo-Hytos chose a local systems integrator called Resim to lead the automation project. Resim has more than 30 years of industrial automation experience and has worked previously on other projects for Argo-Hytos. The designers speci ed four Stäubli TS2-80 Scara robots to handle the electromagnetic control valves during their assembly and end-of-line testing. These robots can theoretically perform up to 200 gripping operations per minute – corresponding to a cycle time of around 0.33 seconds – while maintaining high precision. Z-axis repeat accuracies of up to ±0.004mm are possible in pick-and-place operations. The robots for the new assembly cell do not have to work to such a high degree of accuracy, but precision is nonetheless needed because the valves are pressurised to several hundred bars when in operation. The assembly of their components – especially the valves’ seals – therefore needs to be precise. Automating the end-of-line test station proved to be a particularly challenging task. Argo-Hytos had developed its own testing device for this purpose, and this is where an unexpected obstacle arose. Screwing the valves into the test station caused no problems for the robot. However, when unscrewing the valves, the nal turn on the thread occasionally jammed, bringing the testing operation to a halt. Resim’s designers solved this problem by using the force measurement capabilities built into all four axes of the Stäubli robots, without needing to use external sensors. In this application, the force is measured on the fourth axis, allowing the system’s controller to recognise whether the valve is turning freely in the internal thread of the test device. If the measured force increases, the obstruction can be overcome by reversing the rotary movement briey. If necessary, the process can be repeated several times to achieve the desired result. This ensures that the valve does not jam and the system will not come to an unplanned stop. Because the force measurement function is built into the drive system, no external sensors are needed. The cell was commissioned in 2022 and, more than two years later, it is still said to be working as eciently as the day it was installed. Argo-Hytos has achieved its objective of automating the complex nal assembly of its electromagnetic hydraulic valves. n A hydraulic valve manufacturer is using Scara robots to assemble its electromagnetic valves. A force measurement function built into the robot arms helped to solve a problem on the production line. Two of the four Scara robots that Argo-Hytos is using to assemble electromagnetic valves in a compact cell. Image: Stäubli Tec-Systems Robotics The cell that assembles and tests Argo-Hytos’ hydraulic valves has been installed in a factory in the Czech Republic
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