TPT May 2024

ARTICLE

Fronius

Months later, the robotic welding cell is still just as precise as on the first day and the weld seam is perfectly positioned in the same place. This can also be attributed to the fact that Anton Paar manufactures the components with micrometre precision and joins them with an exemplary level of quality. Turned multiple times The turn-tilt positioner has a media conduit for four flow through lines, two for air and two for argon, and can transmit up to 32 input-output signals (IOs). It is made of plastic and was produced by Anton Paar using 3D printing. If components need to be formed, the handling robot first retrieves the required clamping device from the pallet rack and clamps it on the manipulator with the help of a special clamping system. From that point on, both the air lines for the pneumatic cylinders and the gas lines for flushing with argon are connected. The electrical signals are now also transmitted by the clamping device. The handling robot then positions the components and the system sends the signal for clamping. Forming can now be carried out, followed by welding. The system is designed in such a way that the components can be turned several times on a single clamping device. “It is important to us that all processes and properties that were implemented in the system are open in terms of their repeatability. The matter of whether a turning process is carried out once or a hundred times has to be irrelevant from the perspective of the system. Given that the complexity of our components is constantly changing, we and the experts at Fronius put a lot of energy into making the processes as unrestricted as possible,” added Dr Riemenschneider. Residual oxygen measurement When forming on the tilt-turn positioner, the residual oxygen in the component is measured with the company’s own Oxy 5100 measuring device. It carries out drift-free measurement of the dissolved oxygen in the gas stream in real time during the entire welding process. Normally, the component is fixed between two sections of a line. The forming gas flows in on one side, on the supply line, and out again as a flow of exhaust gas on the other side, where the residual oxygen content is measured. This procedure would be counterproductive for the automated welding process, as the robot would have to take the extra step of inserting and removing an exhaust gas hose during each welding process. The decision was therefore made to place the measuring device in the supply line. As soon as the device reports that the desired residual oxygen content has been reached, welding is started, taking into account a time delay for the time it takes the argon gas to flow through the component. This period is needed to ensure that the required residual oxygen content is not exceeded. The time it takes for the component to be completely filled – the time delay – is determined for each of the components based on a manual measurement and stored in the system. If the component comes up again, the controller can access the values and respond accordingly.

TIG welding of counter coolers with residual oxygen measurement

At the apex of technology It was particularly important for Anton Paar’s welding specialists to be able to combine two welding processes for a component – for example, TIG for welding the root pass and MAG for welding the final run. However, the final choice of welding method depends on the welding calculations and the required resistance of the individual components. “Our welding tests are the deciding factor in whether we use special processes such as cold metal transfer (CMT), pulse multi control (PMC), or low spatter control (LSC). The process we then decide on depends on the wall thickness of the component, on the type of weld, for example square butt or fillet weld, and on the required welding depths and micrographs,” Mr Moik explained. “We need about six or seven tests before we go into series production. If the heat input would be too great due to the nature of the material, the CMT ‘cold’ welding process is of course suitable. If we want to boost productivity by increasing the welding speed, we look at PMC. If welding needs to be particularly low spatter, LSC might be a good choice, primarily because this prevents expensive rework,” he added. The welding data is recorded in the HMI. If the welding specialist finds a fault during the visual inspection, they can check the welding data record to see whether there have been any deviations from the limit values. Every component is subjected to a visual inspection (VI) as a matter of principle and every tenth component undergoes a colour penetration test (PT). This method can be used to detect cracks, pores, and lack of fusion of down to 1µm. The PT-tested metal components are regularly subjected to micrographs at the end of the test cycle. The innovative Fronius processes, a system concept that is both intelligent and flexible, and the ongoing potential to continue developing the robotic welding system, ensure that Anton Paar’s sensitive, high-precision measuring devices will have perfect weld seams for years to come. The company’s welders simultaneously benefit from increased safety and protection of their health as they are shielded from the arc and its emissions by the enclosure and extraction system.

Fronius www.fronius.com

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MAY 2024