From the outset, the emphasis has been on system autonomy for the experts at Anton Paar. Once set up, the welding system needed to be able to process a complete order from start to finish in a single pass. For example, welding a batch of different objects such as oscillator housings, main carriers, or countercoolers. And the system had to be able to do this completely independently and without the intervention of welding specialists.

A range of factors made designing the system especially challenging for engineering and programming teams, including components of various shapes, weights, and sizes, different gripping, positioning, and storage possibilities, the option to use two different welding processes (TIG and MIG/MAG) on a single component, as well as the use of forming gas to protect the components against tarnishing, which is necessary for cylindrical bodies.

“We were looking for a reliable partner who was very similar to us in terms of precision and quality. We wanted someone who would really listen to us, respond to our preferences, and propose sustainable solutions. A partner that would give us a competitive edge for years to come,” explains Daniel Moik, department manager for joining technologies. “Fronius International met these criteria for a sustainable partnership. In close cooperation with our technicians, the welding automation team developed a robotic welding cell that meets our requirements in every respect. On top of that, Fronius is ready to work with us to evolve the system and adapt it to new needs.”

If the track needs to be corrected, the affected teach points can be easily moved by dragging and dropping them. When the approach to the component needs to be changed, the specialists simply press “Reset.” The virtual robot then moves to the home position to start a new approach run. Under real-life conditions, operators would have to complete the time-consuming process of retracting the robot, moving it to the home position with the robot controller, and restarting the teaching process. By opting for the Pathfinder offline programming and simulation software, the experts at Anton Paar not only gain valuable time for welding work but also identify sources of error ahead of time.   

Once a welding program has been set up in Pathfinder, it is translated by a so-called post-processor into the specific code of the Fanuc welding robot. It can then be transferred to the welding system via data transfer using a LAN connection, for example. A key feature that provides effective support for production planning as a whole is the “Determination of cycle time” function, which includes welding speeds as well as gas pre-flow and end crater filling times. Compared to teaching with the robot controller, Pathfinder can achieve a time savings of up to 90%, depending on the component geometry and welding requirements.

The robot controller contains a hierarchically superordinate robot program for each workflow type. This is where the welding programs created with Pathfinder are stored. If a pallet for Workflow 2 is created on the HMI (components are welded directly on the pallet), the robot controller filters the corresponding robot welding programs, and Anton Paar’s welding specialist can conveniently choose between all the programs that are available for Workflow 2 and assign the right one to the pallet. There is also the option to not only use a single welding program but also create an entire work sequence. For example, a TIG program can be created for a pallet, followed by a MAG program (e.g., CMT) in the same sequence. In this case, the robotic welding system would execute both programs one after the other and automatically change the welding process. In addition, the experts at Anton Paar can insert certain special steps into the HMI process. For instance, the system knows the special “Turn component” step, which can be used between the two welding processes (TIG and CMT) if necessary.  

If a specific gripper is required for pallet handling, as described in Workflow 1, the system operator must select it in the system. As previously mentioned, there are a total of six different grippers available, all of which are kept in a gripper station.  

Teaching gripping and depositing positions

The conventional handling sequence itself—picking up the pallet, positioning it for welding, transporting it back, and depositing it—is a standard program and requires no intervention from the operator. This is referred to in the field as an “encapsulated” function. Only the gripping positions have to be specified.  

If a new component is “moved in” and not recognized by one of the depositing or receiving stations, the automatic run pauses. The welding specialist is prompted to start a teaching process with the robot controller—the Fanuc iPendant—and receives step-by-step instructions from the system software. Based on this, the system “learns” the required gripping/depositing position for the relevant station (e.g., for the clipboard). This position is stored in a register and is available for the handling process from that point on. The automatic run can then continue to the next station. If the component is also unknown there, this position must also be taught. Once all the stations have been worked through as described, the handling robot transports all other identical components through the system automatically, without interruption.  

If a pallet should have seven components but there are only three components on it, this is no issue for the system. It detects an “empty grip” and automatically moves to the next component position.

 

Custom-made: the teach pallet

In addition to the standard offset assignment, which favors simple component shapes, Anton Paar wanted to be able to deposit up to 30 metal components at any point on a pallet. Fronius responded by creating the “Teach pallet” function. Selecting this function makes it possible to separately teach the position of each component on the pallet.  

“These two versions, offset and teach pallet, offer us maximum flexibility in component placement,” explains Dr. Ingo Riemenschneider, department manager for production automation. “It doesn’t always make sense for us to define component positions using offset distances. We have to fix some components in different orientations because of their complex shapes.”   

As precise as on the first day—even after months

When the welding specialists want to start a welding process, they use their handheld scanner to scan the item number on the component data sheet.  

“If the system detects the item number and thus the component, it knows about the handling and welding process and starts operation. Everything is controlled via the HMI-T21 RS. The system stores which gripper and which device are needed for each of the components,” explains Riemenschneider. “The same applies to the argon flushing time during forming and the seam time. The system also knows whether and what data is required for process data recording.”  

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 micrometer precision and joins them with an exemplary level of quality.     

Components can be turned multiple times—even during forming

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,” notes Riemenschneider. 

At the apex of welding 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 CMT (cold metal transfer), PMC (pulse multi control), or LSC (low spatter control). 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,” Moik explains. “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.”