Robot continuously welding for 57 minutesPrint this page
The largest production plant of New Holland & Case agricultural machines (CNH) is situated in the Belgian Zedelgem, manufacturing combine harvesters, choppers and bale presses. In 1998, Valk Welding installed here a first Panasonic welding robot installation, later followed by two Nachi spot welding robots. In the meantime, more than ten robots are used in various sections and the number of products welded by robot gradually increases.
The advantages of robot employment is no longer limited to automation. When introducing new models, the clamping tools can be defined in DTPS and the welding programme can be prepared, resulting in a faster start-up of the production. Robot employment has some remarkable advantages for products with a continuous welding time of over one hour. In the middle of 1999, the first Panasonic welding robot was installed on a track in the section where back axles for combine harvesters for all European production plants are being made (3,500 each year). Recently, a second welding robot with fixed position and four workstations was added. Before, the back axles and matching extensions were welded by hand. Willy Devooght, in charge of work preparation: "The long welding time was a bottleneck in our production, because welders regularly had to take a break". Some workpieces require a welding time of 57 minutes per set. By using a welding robot, these workpieces can now be welded faster and without interruptions."
Sheep with five legs
When designing both robot cells, one of the first requirements was: flexible use. Indeed, more variants and types have to be welded simultaneously. That is why the New Holland engineers developed adjustable jigs for the back axles, the length of which can automatically be adjusted. Devooght: "The products are being identified at the moment of clamping, and a total of fifteen variants can be welded simultaneously. The jigs with the back axles are being rotated by Panadice manipulators during welding. The Panasonic welding robot moves over a track of 8 meter and serves 5 clamping places of 4 meter (2 x 2 plus the crosscut side). In total, 50 programmes are permanently available. The welding robot can be employed with a welding duty of over 95%." All clamping places are being filled at the end of the evening shift, in order to continue unmanned welding for a couple of hours."
Automatic exchange
Initially every cell would have to be equipped with another wire and gun, because the material to be welded is not the same for all products. Valk Welding has developed a solution for this limitation, whereby the robot will automatically exchange gun and welding wire. Before, the first robot cell was used to weld extension pieces, with a continuous welding time of 57 min. For these products an extra robot has been taken into use. The welding robot, here in a fixed setting, can serve four clamping places. The position of these clamping places is determined in DTPS. This programming system is used to determine the best position for the exchange of products and for the best accessibility.
"With robot welding you loose the visual monitoring of the manual welder. That is why test series are beforehand analysed piece by piece, and if required, the programme is adjusted", explains Willy Devooght. "But once the welding robot has been perfectly programmed, the quality cannot be equalled by manual welding".
(Source: Vraag en Aanbod no. 41 - 7 October 2003)