Robots at the Center of Cellular Wire-Welding Cells
Motoman Robotics Posted 04/20/2011Automation has supported accelerated growth at Tier-Two and Tier-Three automotive supplier JR Manufacturing, a key link in the Honda supply chain for headrest pillars and welded-wire frames for seats and arm-rest cushions.
Management at automotive supplier JR Manufacturing has a simple and effective strategy:
- Replace menial labor with robotic automation, which improves efficiency =
- Increased competitiveness in the marketplace =
- Growth and the ability to hire more people.
Home to 45 Robots
Founded in 1998, JR Mfg. began by fabricating seamless citronella buckets. Within months of opening its doors, a nearby automotive-seat manufacturer came looking for a supplier of formed seat wires, and the rest is history as they say. In less than 2 yr., JR Mfg. had designed and built its own dedicated pneumatic forming machines to produce formed wire components for Honda seat-cushion and armrest frames.
As its seat-component business grew, the citronella-bucket line was discontinued. New ownership took over in 2003, the 40,000-sq.-ft. plant was expanded and a pair of automated headrest lines moved in, capable of forming and welding headrest fames at up to 300 frames/hr.
Today, 7 years later, the plant is home to 45 robots, various models from Motoman Robotics, West Carrollton, OH. Ten robots throughout the plant perform welding operations, either by arc or resistance processes, while 35 robots move material in and around manufacturing cells. These material-handling robots pluck formed wires and headrests from forming machines and place them into weld fixtures. Most of the action occurs in engineered production cells where material-handling robots sit center stage, surrounded by a set of custom, dedicated wire-forming machines.
In-house Expertise and Process Development
Greg LeFevre, general manager of the JR Mfg. headquarters plant in Fort Recovery, discusses the company’s successful automation strategy that has cost-effectively fueled its growth.
“We build almost all of our own tools in-house, as well as a lot of specialized equipment,” says LeFevre. “That gives us the ability to really control our processes and achieve extremely tight tolerances. Combined with our advanced automation capabilities, that has allowed us to compete in the world market and complete some very aggressive cost-down programs for Honda and its suppliers.”
This year alone the plant has taken on eight new car platforms encompassing over 40 new parts. “Almost every new program includes headrests (which account for half of the firm’s business), and some of the programs include formed wire components and complete seat frames,” says LeFevre.
Describing the evolution of the company’s process for turning cut lengths of steel wire and tubing into seat frames and headrests, LeFevre notes a big move to cellular manufacturing that began in 2005, but really took off in 2008.
“We manufacture 30 different designs of headrests,” he says. “Before we reorganized the plant into production cells, we used to task operators with moving baskets of formed tube and wire parts all over the plant, from the forming machines and into a robotic welding cell. All of that material handling was very inefficient.
“We’re processing 20,000 lb. of wire and another 20,000 lb. of tubing every day,” he adds. “Implementing cellular manufacturing using robotic material handling, with Motoman’s specifically designed handling robots, has paid huge dividends. The strategy has allowed us to reduce our labor costs, and share those cost reductions with our customers.”
Cost-Down Project Saves $100,000
Asked to share an example of a cost-down project realized from its automation approach, LeFevre describes an armrest-frame fabrication cell.
“We built the cell in 2008, with five custom-designed and manufactured wire-forming machines, a resistance-welding robot and two robots to move the material around the cell from machine to machine,” describes LeFevre, “grabbing formed wire segments and loading them in a weld fixture. Implementing cellular manufacturing for this project saved our customer $80,000-$100,000/yr., at a volume of 7,500 welded assemblies/week.”
Moving wire-bending machines into a robotic welding cell is not as simple as it sounds. “You have to provide access for the material-handling robot’s end-of-arm tool,” LeFevre says, “so that the robot can quickly and accurately locate and grasp the wire and tube sections in the proper orientation. Before, when we were fabricating parts by the thousands and moving them in small totes to the remote welding cells, we could design the bending machines to simply drop formed parts into a pan or onto an exit conveyor for manual handling by several operators.
“Now, to allow the bending machines to work inside of a welding cell,” he continues, “we design the bending machines with a main clamp that holds the part from beginning to end, so that the robot’s gripper can access and grab the part. The process is more efficient, dramatically reduces labor content and allows us to reassign laborers to perform more critical functions around the plant. The machine does not release the part until the robot has grabbed it, allowing us to precisely and repeatedly identify and control the orientation of the part so that it can be accurately loaded into the weld fixture. We use sensors to tell each forming-machine clamp that the robot’s gripper has the part, and that it’s OK to release the part.”
Dedicated Lines Achieve Tight Tolerances
Headrest and seat frames are built of either mild-steel wire (seat frames) or high-strength low-alloy steel tubing (headrests). Smaller-diameter wires (8 mm and less) are resistance welded together into frames while larger sections of wire or formed tube (up to 14 mm dia., for headrests) are arc welded. Rear seat-cushion frames average eight to 10 wires each; typical weld time is 30 sec., so that’s how much time the material-handling robots have to move around a cell, pick up each formed wire component and place it into the weld fixture.
“We receive weekly releases for the most part,” says LeFevre, who notes that occasionally the firm also gets daily releases from its customers, testing its manufacturing flexibility. “We build inventory and ship on release,” he adds, with volumes for headrest assemblies in the 6,000-30,000/week range, and 6,000-8,000/week for frames.
Completing most (80 percent) of its work on automated, dedicated production equipment, as opposed to using CNC wire and tube benders, allows JR Mfg. to hold extremely tight tolerances. The firm attains industry-leading regular rejected parts per million (RPPM) of less than 10, with 100-percent on-time delivery, says LeFevre. Dimensional tolerances on individual parts are as little as 0.2 mm, and tolerances on assemblies are equally stringent.
“On a 4-ft.-wide seat frame built up from several welded wire sections, we hold a dimensional tolerance of 3 mm on the completed assembly,” says LeFevre, “quite an accomplishment in light of the tolerance stackup you see when welding that many parts together into an assembly. Critical to our success is our in-house-designed and built fixtures, as well as our custom wire benders—accurate parts make for predictable and, therefore, accurate weldments.”