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Fronius Presents Unmanned Welding Technology
Fronius Posted 10/07/2009
Thanks to the digital revolution, automatic joining processes have been an everyday aspect of technology for several years. Up to now, however, the replacement of wearing parts and the wire spool in gas metal arc welding, as well as the continuous supervision of the joints and the entire process, have involved interruptions, even when robot welding, and were tied to human capability. With its autonomous welding cell project, Fronius developers have overcome these limitations for the first time and have opened up the way for the next stage of the technical evolution: an independent, autonomous welding cell with the highest levels of availability, which does not require human intervention and where the system and its maintenance are decoupled.
At the "Schweißen und Schneiden" trade fair, the technological leader in arc welding will be presenting the prototype of the autonomous welding cell. It consists of a handling and a welding robot as well as special modules for replacing wire spools and wearing parts and monitoring quality. The vision of the unmanned welding cell with a single cockpit for several cells is now becoming a reality.
The three pillars of autonomy
The digital revolution promoted the development away from traditional manual and later semi-mechanised welding towards fully automated robot welding cells, and has significantly influenced the past two decades of welding technology. Fronius developers became renowned as the technology drivers and are now in the process of crossing the threshold to the next stage: from the automatic to the autonomous welding cell. The approach to this solution focuses on three activities that up to now have been performed manually. Firstly, the timely and rapid replacement of wearing parts, e.g. the nozzle and the contact tube, secondly the interruption and loss free replacement of the wire spool and thirdly, reliable quality assurance.
In the near future the autonomous welding cell may well become the nucleus of autonomous welding production. It combines the main achievements of the digital revolution, e.g. the CMT (Cold Metal Transfer) process, gas cooled with a hollow-arm robot, safety welding to automatically stop the system if a person enters the cell, and the pneumatic coupling of wearing parts to the welding torch. All system components are connected via a ProfiNet bus.
"Ghost shift" for maintenance
Production welding no longer needs to be halted in order to replace wearing parts and consumables. This is now achieved by decoupling these maintenance activities from the system, so that it can continue to operate at full availability and at maximum productivity. Each cell contains a wire changing station called "WireXchange" and "TorchXchange", a station for replacing wearing parts, plus additional stations for cleaning the torch and the components (see diagram).
Depending on the application, the replacement of wearing parts, which usually involves the replacement of the torch body, is necessary once or twice per shift. In the autonomous welding cell, this is carried out automatically: If the individually configurable time in the replacement cycle has been reached, the welding process stops for 30 seconds. This is all the time that the automatic system requires to replace the torch neck and the used contact tube with a prepared new one. The robot arm switches over to the wire cutting station, where the wire is cut, rounded and prepared for feeding in. It then retracts automatically out of the torch body. The successful replacement of the torch body is monitored by sensors. The motor system then inserts the wire into the replacement contact tube and the next cycle begins. This 30 second process can be synchronised with the change of components, so that the system remains available without any restrictions.
Similarly, the automatic replacement of the wire drum with WireXchange does not cause any interruptions. All the system operator has to do is ensure that the full drum is ready. If the wire supply for the present drum is about to run out, the welding wire is automatically fed out of the welding torch and the main drive unit. An auxiliary drive unit holds the threaded-in start of the new roll ready. It automatically feeds the tip of the wire into the main wire feed, which then switches horizontally to the new welding wire. This automatic changeover of the welding wire is about 10 times faster than doing it manually. This short period can be synchronised with other automated servicing activities, such as torch cleaning or the blowing out of the wire liner. All necessary maintenance work is thus carried out rather "spookily" in parallel with the production line.
Eyes and ears for quality assurance
Two hollow-arm robots, one of which is linked to the TransPuls Synergic 5000 CMT digital power source for welding, and a second one for handling form the core of the autonomous welding cell. The "mechanical assistant" of the "automatic welder" is also the quality inspector. During the handling, its camera observes the joint being produced in the weld pool. The "Q-Eye" delivers pictures of the welding process - closer, more precisely, and at a higher frequency than a human eye protected by a protective filter could possibly do. The images can be viewed live by the system operator, e.g. on a monitor in the office, and any necessary corrective action can be taken immediately. In this way the system in the autonomous welding cell prevents errors from remaining undetected and consuming large amounts of costly resources, which would continue throughout the rest of the production sequence. The images serve as documentation and as the basis of the continuous improvement process. Here too, image processing systems could also be used to automate the process. A "Q-Ear" can be integrated as required in order to detect suspicious or unusual noises.
With the autonomous welding cell project, Fronius is once again breaking new ground in welding technology. The most important advantage is the almost total availability of the autonomous system. Requirements for maximum availability exist in particular in sectors such as the automobile and component supply industry. Here, conventional robot assisted welding has already reached its productivity limits and the demands with regard to productivity and welding quality for complex components are especially high. It is likely that the first production lines with unmanned welding will be in these sectors.