New trend takes hold in robotic welding

Hollow-shaft robots rapidly on the advance

Hollow-shaft robots are a new generation of robots developed specifically for arc welding applications. The entire hosepack is integrated in the process arm and the torch is located directly in the 6th axis. This makes robot welding more flexible overall, and completely plannable. Weld accessibility is enhanced to a very maximum, and as for the hosepack, this lasts up to two times longer than on conventional robots used for comparable applications. Fronius offers high-grade systems with specific component packages for many different robot manufacturers.

The torch hosepack is integrated right inside the process arm of the robot. Obstacle contours are eliminated, weld accessibility is enhanced and 100% offline simulation of the welding process becomes possible.

For a long time, the only robots on the market were universal ones that had been adapted to perform particular tasks. If you wanted a welding robot, a wirefeeder had to be set up and a suitable torch attached. Of necessity, then, the hosepack had to be routed around the outside, which was highly disadvantageous in terms of handling and, in some cases, even of stability. The torch hosepack was simply a weighty ballast that had to be dragged along with every single motion, which obviously made certain movements more difficult. A disruptive factor, in other words. And one which the new generation of robots happily does without. The torch hosepack is integrated in the robot arm (or “process arm”, as it is also known); there is nothing to dangle, jerk or get in the way of the robot’s manoeuvrability. Instead, it fits pliantly around the robot’s every movement. An innovation that is of 100 % benefit to the welding sector.

Fronius was involved in this development right from the outset. At the time, though, there was no way of foreseeing just how quickly these hollow-shaft robot systems would conquer the market. In retrospect, however, this is easy enough to understand, for the integration of the hosepack in the robot arm brings with it a host of crucial advantages.

Hollow-shaft robots that have been specifically developed for welding tasks are coming increasingly to the fore. Fronius has developed high-grade system components for them, from the hosepack all the way to the welding torch.

Excellent weld accessibility

When no space is taken up by an outside torch hosepack, the slim robot arm can get to many positions that would not otherwise be possible. It can manoeuvre its way into narrow constructions, easily turn and move, and even simply weld around corners without any major eorientation. Even the 6th axle on its own has a rotational speed of more than 2 x 360°/sec. This very great flexibility is due to the fact that the torch is mounted directly in the 6th axis of the robot and no longer needs to be separately attached to holding clamps. This, in turn, results in other, quite different, benefits: faster reorientation, giving productivity gains of around 15 %; better “track-keeping”, because there is now absolutely no whiplash effect from either the torch hosepack or the interconnecting hosepack; a wider applicational range, as tube welds and cladding are now very easily possible and the welding process as a whole is faster and more reliable.

The welding torch is mounted directly on the 6th axis of the robot. This permits the very greatest flexibility in the welding process.

Full offline simulation with no disruptive factors

In simulations, the outside hosepack often used to be regarded as a disruptive factor. Now this disruptive factor has been eliminated altogether. With the result that 100% reliable preliminary planning is now possible, as now there are no “unknowns” to be factored in. This makes it perfectly possible to carry out any offline simulation, with exactly replicable results every time. Even the already highly stable welding process, based on the welding robot and Fronius components, becomes more stable still. This is mainly due to the fact that the hosepack is exactly computed right down to the last centimetre, so that there is only a minimal change in its length through the entire robot motion space. And a constant wirefeed-distance, of course, is vital for a stable weld process. All in all, the change in the length of the torch hosepack is only a tenth (or less) of what it is on conventional robots.

The hosepack is routed directly over the pivot points of the robot axes. This results in better robot-arm stretching characteristics and longer reach, yet reduced hosepack stressing and longer maintenance intervals.

More efficient,compacter, faster

With the hosepack integrated well out of the way, welding robots now automatically have a more slimline design, yet with a bigger reach due to the superior stretching characteristics of the robot arm. In its development work, Fronius took great care to ensure that the hosepack is routed directly over the pivot points of the robot axes. This has a positive effect on the hosepack lengthchange and thus on the stability of the process, as well as on the load burden and the frequency of maintenance. A hosepack integrated in this way has a service life that is around twice as long as in the conventional set-up, and users can better estimate the endurance times. This makes the system as a whole more stable and predictable. No wonder, then, that when it comes to arc welding, conventional robots could soon be reaching the end of the road ...