AT RANCH Manufacturing, builder of the Ranco brand of bottom dump and end dump trailers for more than 30 years, product quality and production efficiency are essential. However, until 2000 the company was experiencing problems in both of these areas, particularly in trailer frame production. A main component of a frame is the crossmember. Crossmembers support all the weight from both the trailer itself and its cargo, and are the link between the trailer and the suspension and axles, as well as the fifthwheel.
According to Ray Lariviere, who handles dealer and product support as well as foreign sales for the company, each trailer has four or five crossmembers, and each requires about 20 feet of welding. “It takes a man one hour to weld one crossmember, so in order to produce two or three trailers a day, we had to have three or four people doing nothing but welding crossmembers together — all day, every day.”
Repetitive work like this is difficult for any welder. Moreover, it's a challenge for any welder to achieve welds with the same quality and at the same speed at 3 pm that he was able to deliver at 8 am. “A welder might do the first crossmember in 50 minutes, and by the end of the day he's taking an hour and a half,” says Lariviere points out. Moreover, to avoid monotony, welders handled the crossmember production on a rotating basis, so not only did quality vary by time of day, but also by the skill level of each welder. Not surprisingly, product quality suffered significantly. ‘With manual welding, we were getting rejects in the 20% to 25% range. For every 100 crossmembers, we would have to reject between 20 and 25 because of quality problems,” says Lariviere.
Dramatic Change
To counter this, Ranco installed an ABB FlexArc K robotic welding system. Since March 2000, when they purchased the robot, Lariviere says the change has been dramatic. “Now we can weld those same crossmembers in about 20 minutes each, and the quality is always the same.” Rejects are few and far between, he says, since the robot usually stops if something is wrong with the gas mixture, wire feed, or some other problem. They are then able to correct the problem, and go back and redo the welding section. Instead of 20% to 25%, “Now we have less than 1% rejects,” he says.
One factor in selecting ABB was location. Because ABB's Fort Collins CO headquarters is only 250 miles from Ranco's facility in Lamar, “We have had no problems getting help when we needed it, although it's been minimal,” Lariviere says. ABB's joystick-type robot “teach” system has made it easy to train Ranco's welders, who did not have robotic welding experience.
The FlexArc K cell is a complete, turnkey system. All components, including the IRB 1400 robot, S4C controller, Orbit 250K positioner, welding power supply, welding torch, and perimeter fencing are mounted on a common base.
The Orbit's dual head and tail stock configuration and its ability to rotate the part for access by the robot are important. Since welds are not all linear, the robot must be able to reach all four sides of the part. The 250K model interchanges like a Ferris wheel rather than horizontally, with a longer distance between head and tail stock than other Orbit models, to accommodate larger work pieces.
Programming the parts has been easy, Lariviere says. They started with one basic program, which ABB installed when they built the system. At that time, Ranco sent Buck Harris, who completed a training program and actually learned to program the robot by working with ABB to program that first crossmember. Buck then trained a second employee to operate the robot. Initially, the robot operator would come in at night to operate the robot and actually make parts, while during the day, Buck came in and programmed new parts. For variations in each program, such as differences in length, thickness, or material, they can make changes on a laptop without disrupting production. The man who programs and operates the robot also builds all fixtures in-house. Changing fixtures takes about 30 minutes.
Options they purchased with the FlexArc K cell include BullsEye, an automatic torch calibration system; an automatic torch cleaner; SmartTac, a tactile sensor that detects the joint location; and ABB's Advanced Weld Control system. AWC ensures that even if parts aren't fitting exactly the same, the robot can still find the proper place to weld.
Lariviere says another benefit of the system is that “it does such a good job, and it's so quick in its welding capability, that we've gone on to (weld) many other parts now on this same robot, not just the crossmembers.” In fact, he says, up to about 40 separate parts are now being welded by the robot. Including several different part configurations, the ABB system is used to weld more than 50 different parts.
The robot currently is operating 20 hours per day, although some of those hours are used for programming as they continue to add new parts. For further information, contact ABB Flexible Automation, Welding Systems Division, 4600 Innovation Dr, Fort Collins CO 80525.