Case Studies / Spot Welding / Agricultural Equipment

Motoman Robot Spot WeldingAchieved cycle time for door assemblies of 4.5 minutes per part (10% faster than requirement). Achieved cycle time for shield door assemblies of 2.5 minutes per part (17% faster than requirement). Spot welds achieved requirements for no weld cracks, thorough fusion, and acceptable aesthetics.

Project Challenges

  • Provide flexibility to spot weld shield door assemblies in the same workcell as door assemblies.
  • Make approximately 110 spot welds per left-hand (LH) or right-hand (RH) door assembly and 75 spot welds per shield door assembly while maintaining near Class 1 “no mar” surface quality. Spot welds must have thorough fusion, the welds cannot have cracks, and weld expulsion must be minimal.
  • Door assemblies 1.2 m and 1.5 m W (4' and 5' W) are 16-gage mild steel and weigh approximately 34 kg (75 lbs.) each. Each door assembly consists of eight components: skin, door handle, hinges, reinforcement straps, and brackets.
  • Shield door assemblies are 16-gage mild steel and weigh approximately 9.07 kg (20 lbs) each. Dimensions are 548-mm x 1,502-mm W (21.6" x 59.13" W).
  • Achieve 5-min. cycle time production rate for door assemblies and a 3-min. cycle time production rate for shield door assemblies (based on two-shift, 8-hr/day production).

Motoman Robotics Solution

Motoman Robotics provided a flexible solution that includes:

  • A Motoman UP200 robot mounted on an 18" riser and steel plate. XRC controller with three additional external axes kits includes Expanded I/O and Expanded Memory modules.
  • Motoman MHT-1500 AC Servo Headstock/Tailstock (HS/TS) positioner rated at 680-kg (1,500-lb.) capacity; 699-mm (27.5") centerline height; 3-m (120") HS to TS distance. Includes manual jog feature.
  • Two Motoman MSR-350S positioners with 1,524 mm (60") diameter table tops with 350-kg (770-lb.) capacity per side. Tables index 180 degrees and back with 2.5-second sweep time, but XRC provides servo control of indexer movement during welding to provide robot with better access to parts. Manual jog feature allows ±180-degree index during load/unload. Positioners are located on steel mounting plates.
  • Water-cooled spot welding transgun with custom 635-mm (25") throat and special tips (large radius tip on one side, flat tip on swivel adapter on the other). Water circulator is customer supplied. Includes tip dresser.
  • Shock sensor located between the spot welding gun and the robot.
  • Common steel base for XRC and spot welding controller.
  • A 4.6-m (15') long enclosed cable tray and cable management tool balancers.
  • Weld controller.
  • Three operator control stations (one “master” and two “slaves”).
  • Two sets of Customer supplied pneumatic fixtures for the indexing positioners and three manually clamped fixtures for the headstock/tailstock. Fixtures included mini PLC to reduce robot I/O requirements.
  • Integrated safety package, including robot zone ring, five light curtains, safety mats, arc curtains, and wire fencing.
Ref: ACS-038
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