More than a flash in the pan
By Chris Anderson
By Chris Anderson
Innovation is the norm at Titan Trailers, a supplier to the hauling and earth-moving industries established by Mike Kloepfer in Harley, Ont., in 1973.
Customers know Titan for its patented Thinwall lightweight and strong extruded-aluminum double-walled trailer panels that help optimize load capacity and fuel efficiency. The firm’s trailers are used to haul garbage, scrap steel, aggregate gravel and similar loads.
In addition to innovation in design, Kloepfer also stresses innovation in manufacturing techniques, as evidenced by the firm’s recent investment in robotic arc welding. “Mike (Kloepfer) continually pushes us to be innovative and inquisitive, and to seek opportunities to apply new technology,” says Tom Pursley, Titan Trailer’s robot specialist and supervisor of the robotics department. “He’s always willing to invest in new equipment to help us do our jobs better.”
Among those jobs is fabricating and welding many of the subassemblies that go into the firm’s line of trailers and earthmoving equipment—subassemblies such as steel and aluminum fifth-wheel couplers, as well as door, frame and floor sections. Couplers, in particular, prove particularly challenging to welders, charged with assembling 30 to 40 components by depositing as many as four-hundred 3-inch-long stitch welds.
“We have to stagger weld locations to balance heat input to the assemblies and avoid distortion,” says Pursley. “This requires our welders to crawl around the weldments quite a bit, a time-consuming and tiring process due to the relatively large size of these weldments. Early in 2011 we began to look for a better way to put these assemblies together.”
The answer was a robotic arc-welding cell. The cell has reduced the average cycle time to weld a steel coupler to 90 minutes, compared to 2.5 hours manually.
Titan’s new cell resides in a new 35,000-square-foot building located a short truck drive from the company’s main assembly building. The new facility also houses some of the fabrication equipment used to prepare subassembly components, including a new waterjet-cutting machine slated to take over much of the precision plate-cutting work previously performed by a high-definition plasma-cutting machine.
“With waterjet,” says Pursley, “fit up improves and we can achieve tighter weld joints that help to avoid burn through and reduce weldmetal consumption. Our jigs and fixtures are easier to build, and weld cycle times have dropped, since we don’t have to spend as much time touch sensing during each weld cycle.”
Touch sensing uses energized welding wire set at a predetermined cut length to physically touch the flat sidewalls of a weld joint. The controller uses triangulation to locate the joint and, should joint location differ from what is programmed, initiate a shift in the robot’s program to compensate.
Seam tracking occurs via a controller option that directs the weaving of the weld wire back and forth in the weld joint. As the wire weaves from side to side, the controller gauges welding current and corrects the robot’s path left-right and up-down to maintain the specified amperage.
Drop-center positioner “really makes this cell go”
Titan Trailers’ robotic arc-welding cell was designed to reduce weld-cycle times on some of its more labour-intensive and high-volume assembles. As a result, the firm has been able to redeploy welders to other operations within the plant and enjoy overall labour savings, while also improving weld quality.
What really makes the cell ideal for Titan’s specific task load, says Pursley, is a servo-driven drop-center tilt/rotate positioner, which provides for as much in-position welding as possible. This proved quite a challenge when manually welding some of the larger assemblies at Titan.
“The positioner really makes this cell go,” Pursley says, “because it allows easy access by the robot-manipulated welding gun to some weld joints that were extremely difficult to reach when manually welding. And being able to rotate and position joints to avoid out-of-position welding is critical to ensuring good-quality welds, particularly on aluminum couplers. To deposit a 90-degree fillet weld, for example, we can position the joint at 45 degrees and develop an optimum penetration profile using gravity to equally penetrate both components.”
The workhorse positioner accepts weld fixtures as large as 173-inches in diameter, and offers a load capacity of 2640 pounds. Its two axes can move independently or with coordinated motion — with each other and with the robot.
Sharing the cell with the drop-center positioner is a head-tailstock positioner, rated to 13,680-pound load capacity. It proves useful for fixturing and positioning heavy steel weldments for Titan’s new line of earthmoving equipment.
Pursley and his robotic cell lead person and programmer Jamie Bowman design and build welding fixtures for the cell, and Bowman says new specialized jigs they have developed have typically reduced assembly fixturing and tack-welding time by half.
“We hold critical dimensional tolerances now in a way that is foolproof,” Bowman says, describing the procedure for welding up a coupler assembly, “holding all dimensions off of the center kingpin. We’re using pneumatic actuators to pull all of the components nice and tight and flat for the robot. And, instead of using several manually operated clamps to fixture everything, we now design the fixtures to include automation — again, another example of the innovation encouraged by management. To set the clamps, the operator only has to flip two switches. Overall, fixturing and tacking a coupler assembly takes about an hour, compared to more than two hours previously.”
Reaching new heights
The overall robotic-welding cell measures 24.5 by 33 feet, and is safeguarded by an eight-foot-tall woven-wire safety fence, arc-flash protection curtains, light curtains at positioner load/unload stations and an access gate with a positive break safety switch. At the heart of the cell is a six-axis extended-reach (122.3-inch) gas-metal-arc-welding robot with 44-pound payload and positioning accuracy to plus or minus 0.006 inches.
A PC-based robot controller directs the cell action, featuring four levels of password protection for as many as 100 users. Among its features: arc-welding-specific keypad buttons and a 26-foot-long cable connecting the Windows CE programming pendant that Pursley and Bowman use to roam the cell during programming.
To streamline new project programming, Titan opted to invest in programming and simulation software. This software provides cycle-time calculations, collision detection and reach analysis.
“The package was easy to cost-justify,” says Pursley, who notes that programming the robot to deposit 300 stitch welds on a coupler can require more than 2000 lines of code. “I can prepare the framework for a new program offline, without having to interrupt production. I can include all of the touch sensing and the welding parameters. Then, all that’s needed at the cell during teach-programming is final tweaking of weld locations.”
A baker’s dozen of programs
Titan launched its production-welding operations with 13 jobs programmed, including 12 different coupler designs. Programming the similar coupler models was made quick and simple by taking advantage of the functionality of the controller.
“We developed several subroutines used to weld one coupler, and then were able to reuse many of the routines as we developed programs for the other couplers,” Pursley says. “This greatly reduced programming time and also eases program maintenance.”
By the end of 2012, Pursley expects to keep the robotic welding cell busy working on some 30 programmed assemblies. And should the cell need to be quickly changed over for welding steel assemblies, Pursley and Bowman say they can switch the cell over from aluminum welding to steel in less than 15 minutes.
Chris Anderson is the product marketing manager, welding, for Yaskawa America Inc.’s Motoman Robotics Division. Reach him at Chris.Anderson@motoman.com. This article originally appeared in the November/December issue of Manufacturing AUTOMATION.