The excellence of automotive robotics applied to general industry. This sums up what SIR Soluzioni Industriali Robotizzate (www.sir-mo.it) has succeeded in creating at System, a Fiorano Modenese firm which has been building industrial automation solutions for a variety of sectors since 1970. System, well known for the quality and reliability of its installations, has come to feel the need for greater flexibility and higher productivity during the welding of drawers.
To deliver increased flexibility and productivity, SIR, in association with System (www.system-group.it) and Comau (www.comau.com), came up with a system that revolutionises the way drawers are welded.
INSIDE THE SYSTEM
The system comprises 4 Comau robots and a series of external controlled axes which automate the entire process. In detail, the robots involved are a Smart NJ 290, a large robot with a wrist payload of 290 kg, for loading and unloading; a long-arm handling robot with a payload of up to 20 kg which positions and retains the omega section-bars for welding in the right positions and, last but not least, a completely new entry in the form of two Smart NJ4 90 Spot Welding Machines, typically used for welding car bodies, which apply the spot welds.
As already mentioned, the automation is completed by a series of controlled axes: a travelling base about ten metres long on which the loading and unloading robot moves (Comau 7th axis); a transfer which handles the drawers in front of the robots, complete with servomotor (Comau 8th axis); two side strips which align the drawer in the correct position for welding, with controlled motion; and a series of controlled motion rollers installed underneath the drawer handling transfer that prevent the sheet metal from giving way and bulging. There is a risk that the sheet metal may not be completely flat during welding, especially when dealing with particularly low thicknesses.
WORKING SEQUENCE
First, the Smart NJ 290 positions the drawer onto which the omega section-bars are to be welded on the transfer. Once in position, the drawer is held in place while the bottom controlled axis sets the sheet metal perfectly horizontal. At this point, the handling robot places the section-bar in the correct position and holds it there until the welding robots have performed the first two spot welds. Once welding has started, the handling robot moves away to collect the next section bar. When welding is complete, the transfer moves to place the drawer in the correct position for the next section bar and the loading and unloading robot travels into position for the operations which follow.
The major novelty about this system is that production no longer has to be stopped; in fact, the operator simply uses a console to enter the code of the drawer to be produced and the system automatically adapts to the process required. This adaptation involves every aspect of the automated process: thicknesses for welding, type of steel used (galvanised or steel plate) number of sheets (2 or 3 sandwiched), section bar positioning, number of spot welds and welding speed.
The installation achieved all the targets set by System. Cycle times have been cut to a minimum, tooling times have disappeared and productivity and flexibility have soared to far higher levels than with any method previously used. Thanks to this robotic system, tooling is now carried out in parallel with other operations, with no down-times: the operator simply types the product code and the entire system presets to produce the new piece, in double-quick time. A truly amazing achievement, with efficiency and productivity increased by 50%. These results are thanks in part to the use of the Smart NJ4 robot – the Comau Spot Welding Machine with integral gripper and transformer on board the gripper – previously only used in panelling. The gripper-mounted transformer has made it possible to deliver high-voltage power directly to the welding point and produce high-quality articles in which the galvanised sheet, just 1.5 mm thick, is welded to perfection.
This innovative, flexible application, constructed by Sir Soluzioni Industrializzati Robotizzate at System, Fiorano Modenese, employs four Comau robots and a series of external controlled axes which automate the entire process.
Davide Passoni
R&D Department
SIR spa
