There are a number of different systems which assist with automated robotic welding. They all have a common aim – prevent cycle time losses and ensure reliable seam quality. Sensors play a central role here; lasers, cameras, or even tactile sensors are designed to detect whether the component is in the right location and whether there are any air gaps present. You can also define how the system responds. However, this additional hardware goes hand in hand with huge expense during installation and operation – and investment costs are often high.
What is more, while many of these systems do increase seam quality, they result in cycle time losses. Their interference contours often also restrict component accessibility, which is why Fronius offers an alternative which can tackle these challenges: high-precision control of the welding wire, combined with the rapid data transfer of the TPS/i power source, means that the wire can also be used as a sensor as well as a filler metal – an approach which opens up completely new possibilities.
Edge detection: correcting the robot path
The robot controller can use this signal to save its current positional data and then correct the robot path by comparing it with the target data. Any component inaccuracies are thus recognized and compensated for. The robot then welds in exactly the right location. Edge detection is already possible for material thicknesses of 0.5 mm and above and sheet thicknesses of up to 20 mm.
Quick robot programming with TeachMode
The robot path must be manually programmed before welding can begin – this is called the teach process. It involves the welder or programmer using a teach pendant to control the robot, scan the component, and save the positional data. In terms of the quality of the weld seam, it is important that a constant distance is maintained between the component and the contact tip across the entire weld seam – this is called the stick out. Assistance systems can also help with this time-consuming, manual process.
TeachMode from Fronius uses a reversing wire movement to prevent the welding wire from being bent when scanning the component. The reversing wire movement begins as soon as the pre-set stick out is undershot by the robot. At the same time, a visual/audible signal informs the user that they must move the welding torch away from the component. This saves the user from having to remove the deformed wire or re-measure the stick out, and speeds up the teach process by up to 30 percent.
SeamTracking: seam tracking during welding
The Fronius SeamTracking assistance system is of particular use in the manufacture of railway or construction vehicles. Where thick sheets or long seams are being welded, the resulting heat can result in distortion or poor positioning of the components. To ensure the robot welds in the right location, a system is needed which reliably detects the welding position during welding. SeamTracking does just that for fillet welds and prepared butt welds – without any additional sensor hardware whatsoever.
To do so, the robot moves back and forth between the two sheets during welding. The robot uses the measured actual values for the individual welding parameters to detect the actual welding position or any deviations. The pre-programmed path is automatically corrected and the robot welds reliably in the correct position.
Detecting a fillet weld position with TouchSense
To compensate for component and clamping tolerances, the robot can use TouchSense to check the position of fillet welds automatically before each weld. To do so, the robot touches the two sheets with the wire electrode or the gas nozzle – which are supplied with a low sensor voltage – at the defined beginning and at the end of the weld seam. The signals contained in the short circuit enable the perfect starting point to be determined.
Save money with wire-based assistance systems
In all, the Fronius robot assistance systems enable more efficient and more reliable robotic welding processes. Rework on components can be significantly reduced and the time and effort spent on subsequent re-programming of robot paths decreases as the robot can correct the weld seam path by itself, all of which reduces production costs. With the Fronius assistance systems, the wire electrode doubles as a sensor as well as filler metal. This saves users money and time spent on maintenance for sensor hardware and does not restrict component accessibility in any way.