Robots and People Making Trucks

Always known for its welding skills, Heil recently has taken welding technology to the next level, creating a virtual village of robotic welders and human operators on the floor of the Fort Payne, Ala., manufacturing plant.

Today, the company is installing its fifth and sixth welding robots. “These are big pieces of equipment,” says Wayne Smith, vice president for manufacturing and general manager of the Fort Payne factory. “Essentially, these robots are welding arms that are used to weld the metal seams of truck bodies.”

Smith calls the move to robotics a natural evolution for Heil, which began evaluating robotics 10 years ago. By 1998, company officials felt that the technology had reached the point where it would benefit their products.

“Welding truck bodies with robots is not easy,” says Richard Mills, manufacturing engineering manager with Heil. “Robots have been used for years in the manufacture of small assemblies produced in very high volumes. A welding cycle for these processes might take three or four minutes. For these applications, you can get a robot for $50,000 to $100,000 and do a lot of different tasks with it.

“The welded assemblies that we tackle are much larger — at a minimum, they are as big as a car,” he continues. “As a result, our welding cycles take at least an hour, with the longest lasting just under two hours. In addition, because a garbage truck has many variations in body dimensions, styles and options, we don't have the large volumes usually associated with robotics manufacture.”

These variations on the theme of robotic welding have required Smith and Mills to customize the company's approach to robotics by touching just about every area of the manufacturing process.

Heil's massive robots come in the form of “C” shaped arms with joints that resemble shoulders, elbows and wrists wielding welding wire. The units, provided by the German-based company Cloos, cost about $500,000 each. To get the robots up and welding, Heil must mount and program each unit to move on tracks, up and down, and all around a truck body assembly pad.

Robotics change more than the welding operation itself. Unlike human welders who can tap a joint square with a hammer, robots cannot. So materials arriving at the welding bays must fit precisely. “You have to get high-quality steel that is very, very flat, with no rust on the surface,” Mills says. “You have to perfect your cutting operations, whether you use lasers or plasmas. The operations that shape parts must be very accurate. You must control the angle of a fold, for example, to a variance of less than 1 degree.”

The fixtures that hold the products during welding also require precision, as do the welding gaps at the seams. According to Mills, these seams must be accurate to at least half the diameter of welding wire, which comes as small as 0.035 of an inch.

Mills and his team design each robot and its supporting tooling from the ground up with 3D ProE computer modeling software. “We actually design the robot for the line and then tell the manufacturer what we want,” Mills says. “The system enables us to replicate what the real robot will do. We produce the program in animation form, which allows us to make sure that the robot can get to all the weld joints.

“This also enables us to update our products when customers request changes,” he explains. “We can respond quickly by modifying the programs in the ProE system without ever taking a robot off the floor for reprogramming.”

Robotics require a lot of work, but Heil's approach makes it pay-off. When the company introduced its new DuraPack family (DPF) of products two years ago, the specifications called for a curved shell body with long visible welds on the outside as part of the design aesthetics.

Welding a DPF body manually, with all the care required, would have taken 12 hours. But robots handle the job in just under 2 hours. While the robots work on one assembly, the system operator tack welds the next body in the line together.

While increased productivity offers benefits, both Smith and Mills say that the most important benefits of robotic welding come with improved quality and throughput.

“The process gives us the high quality we've always been known for,” Mills says. “And we use the productivity gains to increase throughput, thereby reducing delivery times.”

How does the Heil workforce view robotic welding? “We've spent a lot of time over the past three years training our people in this process,” Mills says. “Instead of eliminating jobs, it has upgraded them. Our people relish this and are eager to become robot operators and robot technicians.”