Motoman Robots Arc Welding Motorized Graders (Construction Equipment)

Motoman HP50-20 extended-reach robot on a 5-m servo track uses tandem-arc GMAW process to make heavy-deposition welds on large motor grader frame assemblies fixtured on two different heavy-duty positioners. (MT1-3000 S2X positioner shown.)

Summary

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.

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 19.05-76.2 mm (0.75"-3") thick. Depending on the model, rear frames weigh more than 2,000 kg (4,410 lbs) each; front frames weigh approximately 1,450 kg (3,197 lbs) and mid-section frames weigh approximately 1,500 kg (3,308 lbs). Each frame section requires 50-150 welds, which range from 101.6-2,743.2 mm (4"-9') 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

Motoman Robotics provided a custom HP50-20 welding system, including:

Motoman HP50-20 (extended reach) robot with NX100 robot controller.
Robot base riser.
5-m (16.4') servo track with 1,000-kg (2,205-lb) capacity.
(2) Tandem-arc GMAW torch packages, and 500-amp digital welding power sources, with interface to NX100 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 MT1-3000 S2X two-axis servo-tilt/rotate skyhook positioner with 3,000 kg (6,165-lb) payload capacity. X-axis orbital speed is 0-1.9 rpm. Y-axis orbital speed is 0-2.7 rpm.
Motoman VMH-3000 3SX 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/13,230 lb payload total). Span between headstock/tailstock faceplates is 3.75 meters (12.3'). 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 VMH-3000 3SX positioner; mid-sections on MT1-3000 S2X positioner.