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Robotic Welding System Exceeds Expectations of New Robot User
by Sally Fairchild
Meet customer specification for weld penetration, including holding part tolerances to <0.5 mm.
Stringent customer requirement to document quality of each weld.
Meet required cycle time and production rate.
Meet production rate of 50,000 parts/month based on two shifts.
Operator safety, particularly during part clamping.
Customer was first-time robot user and inexperienced with robotic welding processes.
Motoman supplied an ArcWorld III-1000 system, including:
- SK6 robot with 12" riser.
- Motoman 400-amp, air-cooled TOUGH GUNÆ welding package, including: torch, safety clutch, pancake wire feeder, side-mount process package, universal welding interface, and start-up kit.
- MotoArc 350i power source.
- Motoman ArcSense Monitor (performs a critical role on this project, since the customer must be able to document every weld on every part in case of a failure in the field on the part of their customer’s end-customer (a major automotive company).
- Binzel reamer-type nozzle cleaning station with stand.
- Tregaskiss anti-spatter sprayer.
- Common equipment base for MRC, welding power supply, and options.
- High-speed AC servo-driven reciprocating positioner, 350-kg (770-lb.) capacity per side, 60" diameter tabletop, and 2.5-second index time.
- Comprehensive guarding package, including fence, safety interlocked gate, safety mats, arc screen and curtains.
- Fixturing package with pneumatic clamping.
Motoman designed and supplied custom pneumatic tooling with two-stage clamping. All sensors and clamping are controlled by the MRC controller.
The system makes five welds per part, on each of four parts, for a total of 20 welds — well within the required cycle time. The engine mounts ("cans") consist of .12" steel and the brackets are .24" steel. The welding torches use .045 wire.
The operator loads four "cans" into the Stage 1 fixtures, then triggers the clamping sequence using anti-tiedown opto switches.
When loaded accurately, parts activate mechanical switches designed into the fixtures. These mechanical switches, built to military specifications that repeat within .002" (0.5 mm), were used instead of proximity switches due to the customer’s requirement for extremely close part tolerances of <.05 mm. If all four sensor switches are not activated, the fixture clamping will not close.
If all four switches are activated, the clamps close and the slide portion of the fixtures moves forward. The operator loads U-brackets onto the top of the "can", guided by the fixtures.
Another set of four mechanical sensor switches ensures that all four U-brackets are present and positioned correctly for welding.
The operator then activates the anti-tiedown opto switches and the Stage 2 fixtures clamp.
Next, the operator activates the cycle start button on the operator station to index the parts to the robot for welding.
While the robot is welding parts, the operator unloads completed engine mount final subassemblies and then loads parts for the next cycle.
Motoman provided a robust welding system for this customer's new facility that can be easily relocated as the plant layout changes.
Solution meets customer's specification requirements for weld penetration and arc sense monitoring of each weld.
Motoman's fixturing package met or exceeded customer's expectations.