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Case Studies

Flexible Welding System Increases Productivity to Meet Higher Volume Requirements

by Sally Fairchild
Yaskawa Motoman

Challenges
Need to increase productivity to meet higher volume requirements, but difficult to find skilled welders.

Heavy-deposition GMAW welding on eight frame models that are 10’-12’ (3-3.6 m) long and 5’-6’ (1.07-1.8 m) wide, and weigh 3,500- 4,400 lbs (1,587-1,996 kg) each.

Heavy deposition welding using 0.052" steel wire with 1/8"-3/8" (3.2-9.5 mm) beads on mild steel that is 1/4"-1-1/2" (6.4-50.8 mm) thick.

Manual welding takes one skilled welder 6-7 hours per part.

Manual assembly and pre-tacking requires two hours and part fit-up is not always good.

Motoman Solution
Motoman provided a flexible welding system, including:

  • Dual SK16 robots with single MRC-UL controller.

  • Headstock/tailstock (HS/TS) with 3,000-lb (1,361-kg) capacity each; 6,000-lb. (2,721-kg) capacity total. Adjustable spanners between HS and TS accommodate different models.

  • 50-ft (15.2-m) servo track with separate carriages for HS/TS.

  • Operator station.

  • Two 600-amp water-cooled torches.

  • Motoman ComArc III seam tracking package with high-speed 200-V touch sensing.

  • Two customer-supplied power sources with interface.

  • Nozzle reamer with anti-spatter sprayer.

  • Integrated workcell protection package, including: wire safety fence, light curtains at load/unload zones, and four safety interlocked gates.

 

Fixtures
Motoman provided the holding fixtures on the HS/TS faceplates used to locate the frames on the positioner. The length of spanners between the faceplates is adjustable to accommodate various frame sizes.

 

Operations Sequence
Overview
Frames are pre-assembled and tack welded at a tack station prior to being loaded into the robot cell via overhead crane.

Process Sequence
The operator activates the cycle start buttons on the operator station. The part shuttles into the robot workcell and the weld sequence begins.

Motoman’s ComArc III seam tracking and high-speed 200-V touch-sensing allow the robots to locate the weld joints despite some variation in joint fit-up.

Weld lengths ranged from 4" to 2.5’ (101.6 mm - 762 mm) long, no multi-pass welds are used. The built-in software weave function facilitates heavy-deposition welding.

When welding on the frame is complete, the part automatically shuttles to the unload station. Operators then remove it using an overhead crane.

 

Project Results
Cycle time 1.5 hours per part. Motoman’s robotic solution provides 75-79% time savings, plus labor savings over manual welding that requires one welder 6-7 hours.

Estimated Return on Investment (ROI) of approximately 18 months.

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