Application Stories

Shop Gains Productive Edge with Robotic Welding

F.R. Custom Metal Fabricating Ltd. made a sound investment in the future with the recent purchase of its first robotic welding cell. Faced with a contract to produce a large volume of pallet truck handles, the fabricating shop found it increasingly difficult to maintain the skilled workforce of welders needed to produce consistent, high quality parts at the necessary volume. By adding a two-station Lincoln Electric automated welding system, the firm is now able to meet production and quality goals without trying to find employees willing to work overtime.

Robotics Help Custom Fabricator Tackle a Production Job
F.R., a custom fabricator founded 28 years ago by its President, Alfred Nonnewitz, traditionally has specialized in lower volume, higher quality fabrications, particularly those involving tubular components. For the last three or four years, the company has been producing pallet truck handles on a contract that calls for increasingly higher volumes, now generally between 700 and 1,000 parts per week, according to Bill Nonnewitz, the founder's son.

As with most manufacturing firms throughout North America, F.R. was finding it increasingly difficult to hire the skilled workers needed to maintain the quality and volume of its production. And with today's busy lifestyle, employees were less willing to work long overtime hours to keep up with the demand.

Robotics Not Just for Larger Shops
After meeting with representatives of The Lincoln Electric Company's Automated Systems Group (ASG), Alfred and Bill Nonnewitz concluded that the benefits of automating the handle-welding operation would be worth the investment.

Six-Axis Fanuc Arc Mate 100The result is a complete two-station work cell that incorporates a six-axis Fanuc ARC Mate™100i robot equipped with a SYSTEM R-J3™ controller, a Lincoln Power Wave® 450 power source, and a Binzel ROBO-WH-455-22 water-cooled torch.

Safety was built into the welding cell with the addition of safety zone rings (limit switches) that prevent the robot and welding torch from going to the station where the operator is working on the next setup until the area is cleared. In addition, each station has a safety mat that prevents the robot from coming to that station if the operator is standing on the mat. Further safety protection is provided by a breakaway nozzle that minimizes damage in case the torch hits any part of the workstation or the parts being welded.

All components are mild steel, with the handle and brackets being 16 gage and the tube being 14 gage. Welds are made with .035" diameter Lincoln SuperArc® L-56™ (AWS ER70S-6) electrode, which includes extra deoxidizers that provide cleaning action and improve weld quality. Since the handles are used to move pallet trucks that weigh up to 5000 lbs., weld integrity is critical to meeting the stresses they must withstand. All welds are fillets, but the welds that join the round handle to the square tube are especially critical. Bill Nonnewitz explains, "The welding power source is capable of making a full regulated controlled weld without spatter or burn-through. Because we only have 1/16" on a side, the welds can't extend out very much. They have to be good, and the penetration has to be consistent."

A Packaged Approach to Automated Welding
Jim Grant explains that the entire workstation is modular and can be moved with a forklift. "It's essentially a plug-and-play robot that was placed on the floor as a complete unit, pre-programmed for the parts they make. Everything is mounted on a platform that keeps the units in proper relationship to one another and allows the cell to be moved easily to another location if needed."

The Lincoln PowerWave® 450 is a sophisticated power source that gives the company significant advantages, with cost savings that are expected to more than offset a slightly higher initial investment. First is the unit's capability for Pulsed MIG welding, an advanced welding mode that combines the best qualities of all other metal transfer modes without their disadvantages. Its lower heat input prevents burn-through on thin metals. Spatter and fume are reduced as well, which improves the working environment and reduces costs. Since only one wire size is required, wire and gas costs are also lower, and the process delivers higher deposition rates than other processes, so productivity is greater. In addition, the power source can be updated easily with new software, an important advantage that protects the company's investment.

The Fanuc ARC Mate™100i robot is designed with integral utilities to improve reliability and setup time. The wire feed motor cable, gas line and air line are all inside the robot arm. Its high motion speeds help improve productivity, and advanced servo-control features allow faster and smoother point-to-point motion.

The FANUC Robotics System R-J3 controller is completely integrated with the robot itself, which allows flexible work cell layout and easy installation. It utilizes the most advanced software with features that include welding restart, scratch start, and on-the-fly weld adjustment. Mirror image utility allows the programmer to shift an existing program and also to invert it, which is extremely useful with F.R. Custom Metal's two-station mirror-image cell. The program also allows starting and stopping the programmed welding sequence from the Teach Pendant, which features commands in English for ease of use.

The Binzel ROBO-WH-455-22W torch includes a wire-cutting feature that helps speed up maintenance and maintain productivity. Lincoln Electric's Jim Grant explains, "If the operator has to pull the nozzle out for cleaning or adjustment, it is designed to cut the wire cleanly. There is a key that releases the whole bottom nozzle assembly and cuts the wire, so you can make any adjustments on the bench instead of trying to make them while the nozzle is on the robot or having to cut the wire to remove the nozzle."

While no comparative figures were kept, the improvements in product quality and productivity have been significant since the company added the robotic cell, and the labor shortages it experienced earlier have been minimized. Bill Nonnewitz says that, since installing the robotic system a few months ago, the company has already seen significant savings, both in reduced overtime costs and in rework and scrap losses.

Originally Written 4/16/01