Case Studies / Arc Welding / Crane Turntable Weldments (Construction Equipment)

Motoman Robots Arc WeldingFlexible robot system welds 10 different pre-tacked turntable frame weldments. Different parts can be welded on the two headstock/tailstock positioners, but cycle times are balanced to optimize productivity. Robot system easily achieves required 1.79-hour steady-state takt time. Robotic system improves productivity and provides consistent, high-quality welds that meet customer’s specifications.

Project Challenges

  • Automate welding of pre-tacked turntable frame weldments to improve productivity.
  • Provide flexible robotic system that can produce the required 10 different parts, which weigh approximately 651.8-1216.1 kg (1,437-2,681 lbs).
  • Weldments are comprised of high-strength steel and range from approximately 3.7-4.9 m (12-16') L, 0.9-1.5 m (3-5') W and 1.2-1.5 m (4-5') H.
  • Depending on the model, parts require approximately 200-300 welds, ranging from 25.4 mm (1") L with 4.8 mm ( 3/16"/0.1875") fillet welds to approximately 1,818.8 mm (6') L 12.7 mm (0.5") fillet welds. Single and multi-pass welds are required.
  • Meet customer’s specifications for weld quality and consistency.
  • Achieve steady-state takt time (the rate of time that a completed product is finished in regular production) on all required part numbers that is no greater than 1.79 hours (107.4 minutes), not including any necessary manual welding. Weld time is defined as part-to-part exchange, including tooling changes, Touch-Sense, nozzle cleaning, and loading/unloading of parts.

Motoman Robotics Solution

Motoman Robotics provided a highly flexible custom welding solution, including:

  • (6) HP50-20 robots NX100 controllers.
  • (4) MotoSweep-O HD robot servo beams that provide radial transport on a C-frame base with ±0.10 mm (0.004") accuracy.
  • 17.7-m (58') L servo track with two 2-m (6.5') L carriages.
  • (6) Miller 450-Amp AutoAxcess weld packages.
  • (6) 600-Amp water-cooled torch packages with water circulators.
  • (6) Motoman ComArc (200-V) touch-sense packages with seam-tracking.
  • (6) Multi-layer software packages.
  • (6) Reamer/sprayer nozzle cleaning stations.
  • (8) Toolsight™ torch alignment packages.
  • (2) Headstock/tailstock positioners with 7,257.5-kg (16,000-lb) rated HS/TS load at 150 mm (5.9") off-center CG. Span between HS/TS faceplates is 6.2 m (20.34').
  • Custom fixturing package with hydraulic clamping.
  • Operator station on stand-alone pedestal.
  • Cell guarding package that complies with ANSI/RIA-15.06-1999 safety standard. Includes: 3.05-m (10') woven wire perimeter safety fence; arc flash protection curtains; light curtain separating weld zones; quad-fold barrier doors at positioner load/unload stations; and (2) 3-color safety beacon lights with audible alarms.

Fixtures/Tooling Details

Motoman Robotics provided hydraulically clamped tooling used to locate parts on the headstock/tailstock positioners. Fixturing package includes two (drop-center type) spanner back-bones with a mounting surface for turntable bearing plates. Some manual change-out is required between the part models. Parts are mounted on locating pins.

Ref: ACS-100

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