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A fabrication moving overhead via crane is not an unusual occurrence in a shop. But as the fabrication becomes larger, it definitely becomes more noticeable—or, at least, more of a concern.
Consider these applications:
A locomotive manufacturer requires an overhead crane to move the entire assembly, weighing more than 500,000 lbs., from one staging area to the other, each time requiring the shop floor to be cleared of personnel before the assembly is lifted and transported.
An agricultural equipment manufacturer brings two very heavy sections to an assembly area, where the two pieces are lifted with cranes and joined together to produce a part for an even larger assembly.
An overhead crane is needed to move a huge weldment from one assembly area to another, where it will be positioned carefully onto a head-and-tail-stock positioner for final welds.
In all of these instances, a lot of weight is being dangled above a shop floor. With the right safety precautions in place, most employees are likely moved out of the area before these large fabrications are transported by overhead crane, but someone still needs to make last-minute adjustments before pickup and position the fabrications when they are finally dropped into place. More than likely, plenty of valuable machine tools also are exposed to potential damage as the huge fabrications are moved into place with overhead cranes.
What many manufacturers and metal fabricators might not realize is that ground-based automated material handling options are available that can move objects weighing tons. These systems have been in use for years to move things like high-capacity cable reels, wind turbine blades, and molds and dies, but they are increasingly being considered for large fabrications and heavy weldments.
“People are coming to us looking for ground-based solutions as alternatives to overhead cranes that involve slinging and hoisting. They want to avoid people getting hurt and remove overhead bottlenecks to production flow,” said Jason Stoecker, CEO and owner, Align Production Systems.
Safety First
Stoecker’s company specializes in moving the big, awkward, and heavy. It dates back to the invention of air caster technology in the 1950s. Much like a hovercraft, an air caster uses a thin layer of air to lift and maneuver a load that sits on top of it. A patent owner of one type of air caster technology left General Motors and opened up Airfloat Corp. in 1967 in Decatur, Ill.; that company is now a part of Align.
Stoecker said the technology is incredibly good and cost-effective at moving heavy loads, but its use is conditional: It requires a relatively smooth, continuous surface on which the air casters can move, along with an air supply line, both of which can be tough obstacles to overcome given the need for infrastructure investments and patterns of movement. However, the air caster technology is still used often in transporters, rigging, and for other material handling systems such as turntables.
Given the limitations of air casters, Align has taken on more work involving wheel-based material handling equipment. Over the years, this has led to the development of battery-powered wheel-based systems for large-scale manufacturing settings with loads measured in the hundreds of thousands—and sometimes millions—of pounds.
Those automated guided vehicles (AGVs) are now being used to move incredibly heavy and large loads:
In the case of the locomotive manufacturer, an AGV is able to move that 500,000-lb. assembly from one bay to the next. An overhead crane is used only one time—to move the locomotive from final assembly to the railroad tracks for delivery.
At the agricultural equipment manufacturer, two AGVs deliver the two separate fabrications to the assembly area, where they are positioned and married together while remaining on the AGVs. Neither of the heavy fabrications has to be lifted or maneuvered by a crane. In fact, the married pieces can proceed to the next step in the manufacturing process with the two AGVs working in unison.
The huge weldment is now delivered to the welding cell by a transporter and moved directly into position on the head-and-tail-stock positioner, where it is locked in. The transporter then exits the cell until the welding is done and returns automatically to remove it when welding is complete.
Stoecker said that Align not only can deliver the vehicles used to move the large fabrications around the shop floor, but also the supporting engineered-to-order equipment like turntables, positioners, and lifts. The company strives to be a one-stop shop for these large projects.
To move a large workpiece, such as one weighing more than 100,000 lbs., it sometimes makes sense to use two automated tuggers rather than one very large AGV.
And those projects appear to be getting larger.
“Customers used to utilize overhead cranes and fork trucks to move and position 5,000-lb. loads all the time, but with expansion of manufacturing and technologies, every company is tasked with larger and larger demand, coupled with increasing safety and ergonomic requirements. Real estate space is expensive, and size and safety often work in competition with one another. Fork trucks and overhead solutions are simply no longer meeting the demand, let alone the ultimate desire to be autonomous,” Stoecker said.
Technology Keeps Improving
It wasn’t too long ago that AGVs required wire to be buried in the shop floor. The vehicles would follow that wired path. This, of course, did not make these automated material movers very flexible.
Stoecker said AGV technology is “evolving fast” and obsoleting old methodologies quickly, and he sees other technology being used today that might follow suit in the future. That’s how fast the technology is developing and being commercialized.
“It’s extending into heavy industry because everything is getting cheaper, like battery technology, and it’s getting better, smarter, and more capable,” he said.
Just consider navigation technology. Laser scanners on AGVs can be used in conjunction with reflectors throughout a facility for high positional accuracy. For facilities that routinely reshuffle the layout, vehicles with onboard sensors are good for detecting walls, columns, and other structural features. For applications with repetitive stops, radio frequency tags or QR codes can be used to direct vehicles along their path, ensuring pinpoint accuracy. All of these tools can help manufacturers and metal fabricators with their large material handling projects.
Stoecker said most of the work that his company is involved with involves engineered-to-order systems. They might start with a basic product, like a common vehicle platform, and then tweak it to meet a very specific set of criteria in a plant.
To illustrate the point, he described the use of a fork truck to pick up large loads—a familiar sight in all sorts of fabrication facilities. This type of job requires a very large and heavy truck to lift a large and heavy load off the floor to allow for movement. It’s not the safest setup.
“We can build a unit where the forks really don’t leave the ground. They have wheels on them, and hydraulics pick up the large load,” he said. “It’s like the old pallet jacks but able to handle projects ranging from 50,000 lbs. to well over 200,000 lbs.” An operator can maneuver the vehicle with an RF controller and get it to where it needs to go.
Something to Keep in Mind
This type of alternative material handling approach might not fit the needs of all manufacturers and fabricators, but it makes sense for some. Until you see an entire bus frame or a large tractor assembly moving freely around a plant floor while sitting on top of a large AGV, you really don’t have an idea of what might be possible with this type of technology.
There’s a reason that AGVs, and not cranes or even forklifts, are part of the picture when people start describing factories of the future. They allow organizations to keep their employees safe and to focus on tasks that deliver the maximum amount of value to the work, which does not include moving material around on a pallet. Why shouldn’t this vision of the future include heavy fabrication shops as well?
