By CLARE GOLDSBERRY,
associate editor

(top photo) A bearing being plasma-transferred arc welded by a CNC robot. (bottom photo) The black box is the robot's controller.


Computer-rendered 3D models of single- and dual-torch, CNC/robotic plasma welding systems.


Designing automation for unique welding and material handling applications requires thinking outside the box, as well as suppliers who offer flexible products that can be adapted to accommodate these new processes. Dan Allford, president of ARC Specialties

(www.arcspecialties.com)

Recently, the company has teamed with ABB Inc.'s (www.abb.com) robotics division that is providing the robots for ARC's automation cells. ESAB Welding and Cutting Products (www.esab.com) provides the power supplies.

"Flexible suppliers support ARC in a big way by actually encouraging us to find solutions to some of these unique welding applications our customers need," Allford said. "One of the primary reasons we chose ABB's robots is that many of our automation applications require that we customize the automated welding cell, and ABB's open architecture allows us to do that."

ARC Specialties has its niche in the more unusual welding jobs that include wire and powder feed plasma welding, and hot wire TIG. The company was founded in 1983 to provide welding services and welding automation to industry.

The majority of all welding robots are used for MIG welding, but since ARC Specialties plays in the non-MIG and non-standard welding applications arenas, suppliers ABB and ESAB lend themselves to that. One of the most unique automated welding cell projects that ARC developed was one that replaced atomic hydrogen welding with powder feed plasma overlay welding. Allford said that while atomic hydrogen welding is an antiquated process, it still is used in certain hard-facing applications. Additionally, he said, atomic hydrogen welding can be dangerous, the equipment is no longer manufactured, and the process is impossible to automate.

ARC's customer wanted to convert its process to a robotic solution. That required that the process be changed from atomic hydrogen to plasma-transferred arc with powder feed. In turn, the weld process and the filler materials had to be changed. "We found that we needed to manipulate the part under the torch using the robot rather than the other way around. Because the plasma process generally requires the torch to remain nearly vertical, it made sense to have the torch mounted and the part moving under it. With the robot handling the part, it allowed us to use two torches and do two operations all within the cell," Allford said.

ARC used two ESAB 350 MPI constant current power supplies directly controlled by the ARC 6 system, which also controlled the ABB robot. "The 350 MPI is normally a TIG welder. So ESAB cooperated with us to integrate the 350 MPI as a plasma power supply to allow us to use the 350 MPI in the cell," he added.

The ARC 6 is a CNC controller. That is another unusual aspect of the cell: the controller monitors and adjusts the process while allowing the ABB robot to do what it does best — motion control of the part.

"By allowing the robot to handle the part manipulation during the welding, we were also able to integrate loading and unloading of the parts. The robot positions the part under the torch, sets it aside, then loads another part for a totally integrated material handling system using a quick-change tool holder to achieve this," Allford said.