Securely Welded With the FANUC ARC Welding Robot

The central focus of Axzion’s production in Neustrelitz is lifting equipment and transport cradles with large dimensions. Such cradles are required, for example, to safely transport rotor blades for onshore and offshore wind turbines. Grippers are one of the most spectacular pieces of lifting equipment, and they are for example used to lift huge pipes of a diameter of up to six metres and a length of 30, 40 or even 60 metres.

For Axzion it was important that its welding solution should be a portal system for welding components up to 10 m in length and with a piece weight of up to 5,000 kg. The plan was to use an EWM welding current source as the best experiences with manual welding had been shown by the EWM “forceArc” process. In addition, the robot should work with both single-wire and tandem torches and the system should have the option of off-line programming. 

The positioner on which the clamped workpieces can also be rotated is correspondingly large. Traverse and rotation axes are integrated as servo axes directly into the robot controller and can be controlled by the R-30𝑖B robot controller. Welding engineer Ray Baumann classifies the control of the workpiece axis of rotation as “very tricky”. Even with the centre of gravity lying outside the axis of rotation, the axis rotates entirely evenly so that the welding robot can also perform its work evenly.

Baumann: “We do not carry out any out of position welding.” Nearly all welded seams are welded in PA and PB positions. For this purpose, a single-wire torch or a tandem torch is used on the robot, which are located in a changeover device on the portal. There are two corresponding torch cleaning stations. A torch cleaning procedure takes place at the tandem torch approximately once every hour. An indoor crane is used to place the pre-tacked workpiece on the rotary table. Different mountings, holders and clamping elements hold the workpiece in such a way that it can be welded free of distortion. In order to really be safe, operator Ronny Hahn sometimes makes an additional welding point. 

Finally, the free access of the robot to the workpiece must not be made more difficult by clamping elements. And the operator must ensure clamping that is suitable for the robot, so that it can also reach the weld seam with the best possible angle of incidence of the torch.

While the robot is working on one part of the system, the other part of the system can be fitted with components that are not too large or the next workpiece can be tacked. Sometimes, the ARC Mate robot from FANUC still needs a bit of support and oversight from Ronny Hahn. By observing the process through the welding goggles, he can improve the torch angle here and there, or help the seam tracking sensor via the iPendant programming hand tool.