Construction Vehicles

Project Challenges

• Provide flexible robotic welding system to automate welding of new design of motor grader with seven models. Front, middle and rear assemblies are manually pre-tacked prior to robotic welding, then manually welded together to form the final frame.
• Large, heavy parts consist of mild steel plate 19-76 mm thick. Depending on the model, rear frames weigh more than 2,000 kg each; front frames weigh approximately 1,450 kg and mid-section frames weigh approximately 1,500 kg. Each frame section requires 50-150 welds, which range from 102-2,743 mm L.
• Improve productivity and shorten lead time.
• Reduce dependency on skilled human welders due to shortage.
• Make aesthetically pleasing welds on outside of grader frame that do not need to be ground down prior to being painted.
• Accommodate low ceiling in plant with non-gantry robot system.

Motoman Robotics Solution

Yaskawa Motoman provided a custom welding system, including:

• Motoman® 20-kg payload, extended reach robot with controller and base riser.
• 5-m servo track with 1,000-kg capacity.
• (2) Tandem-arc GMAW torch packages, and 500-Amp digital welding power sources, with interface to robot controller.
• 1,000-lb bulk wire reels with high-speed wire-assist feeders.
• Automatic wire cutter and tandem torch reamer.
• 200-V Com-Arc seam-tracking and touch-sensing package.
• Motoman two-axis servo-tilt/rotate skyhook positioner with 3,000 kg payload capacity. X-axis orbital speed is 0-1.9 rpm. Y-axis orbital speed is 0-2.7 rpm.
• Motoman three-axis, two-station servo-powered positioner. Includes two headstock/tailstock positioners mounted on a rotating base axis. Each headstock/tailstock has a 3,000 kg payload (6,000 kg payload total). Span between headstock/tailstock faceplates is 3.75 meters. Index time is 5 seconds.
• (2) Operator stations (one per welding station). Functions: Job Start, Emergency Stop, Hold, Alarm Reset, and Servo Power-up. Palm button for cycle start activation. Ready signal light and alarm indication light. Positioner auto/manual switch. Thumbwheel switch for program selection (up to 100 programmed jobs) and manual positioner jog joystick.
• Workcell protection package, including safety fencing, light curtains, and three safety-interlocked access gates. Meets Canadian CSA Z434-03 robotic safety code as well as ANSI/RIA R16.06-1999 safety standard.

Fixtures/Tooling Details

Customer provided manual fixtures for this project. Operators manually bolt frame parts onto the two positioners. Robot welds grader front and rear assemblies on the headstock/tailstock positioner; mid-sections on the skyhook positoner.

Project Results

• Robot system meets or exceeds all project goals. Allows customer to build on two shifts what would have taken three shifts, eliminating a production bottleneck.
• System requires two operators versus 10-11 skilled welders.
• Flexible system accommodates various models/batch runs with easy changeover; operator simply selects new program using robot teach pendant.
• Tandem arc welding is at least 2.5 times faster and can eliminate need for multiple passes on long, heavy deposition welds, saving cycle time.