Robotics Notebook: Three-robot Cell Welds Crane Outriggers
February 20, 2009
Like many heavy equipment manufacturers, Manitowoc Cranes (Manitowoc, WI) is having a difficult time finding enough skilled welders to meet its production needs. It is also continually looking for ways to improve the quality and consistency of its products while cutting its manufacturing costs.
Recently, the company accomplished all these objectives by implementing a three-robot tandem-arc welding cell at its plant in Shady Grove, PA. The system assembles outrigger beams for the company’s construction cranes, and has been configured to weld 26 different beam types measuring from five to 12 feet. The finished beams, which are made of mild steel, weigh 500 to 1,700 pounds.
“The results have been stellar,” says Manitowoc senior manufacturing engineer Peter Johnson. “Beams with seven to 10 welds…that formerly took three to four hours to weld manually can now be welded on average in 17 to 18 minutes, with some parts finished in as little as 13 minutes.”
In addition, Johnson says the cell has allowed his company to do some of the welding work that it had previously been forced to outsource.
“We’ve been able to bring production back in-house, saving the company a tremendous amount of time and money. Having the robots has also allowed us to redeploy skilled manual welders elsewhere in the plant,” Johnson says.
The workcell includes three six-axis HP20 robots from Motoman Inc. (West Carrollton, OH), each of which provides a 20-kilogram payload, a reach of 1,717 millimeters and repeatability of ±0.06 millimeter. Each robot is equipped with a TimeTwin TPS 5000 digital welding package and a Robacta Twin Compact 900-amp water-cooled tandem-arc GMAW torch package from Fronius USA LLC (Brighton, MI).
A pair of MHT-3000 headstock-tailstock positioners-also from Motoman-locates the beams for welding. Motoman also provided a set of custom hydraulic clamping fixtures for the two headstock-tailstock positioners. A large spanner between the faceplates can be adjusted to accommodate the different outrigger beam lengths.
For more on robotic welding, call 937-847-6200 or visit www.motoman.com.
For more on automated welding equipment, call 810-220-4414 or visit www.fronius-usa.com.
For more on robots, including a robots-for-assembly tutorial, visit the Robotic Industries Association at www.robotics.org.