Case Studies / Part Transfer / Skid Steer ROPS Cab Assemblies

Motoman Robots Arc Welding and HandlingDesired cycle time for “jigless” cell was 6 minutes; robot system easily achieves 5.5-minute cycle time for welding ROPS cab assemblies. Three pre-tacked assemblies can be staged on the infeed conveyor, and three welded assemblies can be queued on the outfeed conveyor, with a fourth assembly in the HP600’s EOA tooling, providing approximately 30 minutes of unattended production. Robot system provides high-quality, consistent welds and increases part throughput. Compact cell layout accommodates customer’s preferred part flow.

Project Challenges

  • Weld pre-tacked ROPS (roll-over protection system) cab assemblies that are approximately 1,320.8 mm L x 863.6 mm W x 1,168.4 mm H (52" x 34" x 46") and weigh approximately 113 kg (249.2 lbs). Parts consist of 3.2-4.8 mm (1/8"–3/16") thick steel and require approximately 50 single-pass welds in various lengths ranging from 25.4-50.8 mm (1-2") to 457.2-609.6 mm (1.5-2') each.
  • Improve weld quality and part throughput.
  • Provide a compact welding cell to accommodate customer’s preferred part flow.
  • Achieve desired cycle time of approximately 6 minutes per assembly.
  • Stage enough pre-tacked parts and queue sufficient welded assemblies to accommodate approximately 30 minutes of unattended production.

Motoman Robotics Solution

Motoman Robotics provided a custom “jigless” welding solution, including:

  • Two EA1900N “Expert Arc” welding robots.
  • HP600 robot (for “jigless” part positioning).
  • NX100-TR3C controller (controls all three robots).
  • Custom end-of-arm tooling (gripper fixture) for HP600 robot.
  • Infeed conveyor – 4.5 m (15') L table-top chain conveyor with three separate driven zones. Stages up to three pre-tacked cabs. Includes locating stop and photo eyes at start and stop positions.
  • Outfeed conveyor – 4.5 m (15') L table-top chain conveyor with one driven zone. Holds up to three welded cabs. (HP600 can hold fourth welded cab.)
  • Operator station on stand-alone pedestal.
  • Integration of Customer supplied Miller Auto-Axcess welding packages.
  • (2) Water-cooled 450-Amp torches and weld dress out packages with provisions for 13.6 kg (30-lb) side-mount wire spools.
  • (2) Miller high-speed touch-sensing functions.
  • Cell guarding package that complies with ANSI-RIA R15.06- 1999 safety standards. Includes wire safety fencing with one access gate and positive-break safety switch; arc flash protection curtains; and “dog-house” fence enclosures at conveyor inlet and outlet.

Fixtures/Tooling Details

For this "jigless” system, Motoman Robotics provided the custom end-of-arm tooling for the HP600 robot. Hydraulically actuated EOA gripper fixture is designed to hold one pre-tacked ROPS cab assembly at a time. The gripper fixture constrains the assembly during the welding process to ensure consistency and repeatability of welds. Customer is responsible for providing pretacked parts within allowable tolerances in all directions to allow proper welding.

Ref: ACS-103

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