Imagine walking into a material handling equipment maintenance and repair shop, pulling standard components off the shelf, and—with relatively little time and effort—turning an ordinary industrial tow tractor or forklift into an automatic guided vehicle (AGV).

That day isn't here just yet, but it's closer than you might think. An automation project at a Toyota auto manufacturing plant in Georgetown, Ky., has shown that it's possible to retrofit some types of manual equipment quickly and easily, earning a big return in terms of cost, labor, efficiency, and flexibility. Although the project involved a manufacturing environment, it may well serve as a prototype for bringing more AGVs to material handling environments, where they have yet to make major inroads due to their cost and complexity.

TOW TRACTOR TRANSFORMATION
Toyota Motor Manufacturing Kentucky Inc. (TMMK) makes the Camry, Venza, and Avalon models at the Georgetown facility, a 1,300-acre complex encompassing some 7.5 million square feet of manufacturing and assembly space. Like all Toyota operations, the Georgetown plant adheres to the Toyota Production System, also known as "just-in-time" or "lean" manufacturing.

Over the years, Toyota had honed production at the Georgetown plant to a high level of efficiency. But there was still room for improvement when it came to the internal movement of parts. The factory, built in 1988, is not as compact as newer facilities. As a result, workers delivering materials to the body-weld department had to drive long distances, navigating congested areas to drop flow racks and palletloads of parts at work cells. Sudden stops, complicated workflow paths, and the occasional traffic jam or collision led to product damage and delayed deliveries.

A team assigned to study the problem determined that automating the transportation of parts to the 1 million-square-foot body-weld area—in essence, taking human drivers out of the equation—would eliminate most of the delay and damage problems. Their conclusion may not be very surprising. What is surprising is the way TMMK accomplished that objective: Instead of purchasing new equipment, the factory chose to retrofit 22 of its Toyota 24-volt, AC-drive tow tractors with locally built automation kits that turned them into automatic guided vehicles.

To develop these "home-grown" AGVs, TMMK worked with two local business partners—AutoGuide, an automation specialist led by AGV innovator Paul J. Perry, and Industrial Concepts Inc. (ICI), a developer of custom machinery and control systems whose president, Tim Taylor, is a former TMMK mechanical whiz. (AutoGuide and ICI are closely allied; the two share a facility across the street from TMMK, and ICI's executives have an ownership stake in AutoGuide.)

Utilizing the same off-the-shelf devices already in use for other types of AGVs at TMMK, AutoGuide outfitted the 10,000-pound-capacity tow tractors with obstacle and guidance sensors, radio-frequency modems, RFID tag readers, and a touchscreen programmable logic controller (PLC) interface, among other technologies. All of the components are contained in a removable attachment designed by AutoGuide. Installation is a simple matter of drilling six holes in a tractor's chassis, and is the only physical change required, according to Tim Meyer, Toyota Production System solutions and AGV product manager for Toyota Material Handling U.S.A. Inc.

Flexibility was another reason TMMK chose to convert standard, manual equipment to AGVs. The stand-alone attachments can be installed either at the time of purchase or lease, or after the vehicles go into service, and they can be easily removed and reinstalled on other vehicles, Meyer explained during a tour of TMMK. Drivers can switch the tractors from automatic to manual mode simply by stepping on a pressure-sensitive mat in the driver's compartment.

NAVIGATING "SPAGHETTI JUNCTION"
Before the AGVs arrived in the body-weld department, manned tow tractors dropped off flow racks and pallets full of parts alongside each of the robotic welding cells, which were located on both sides of a wide aisle. Team members then picked up the parts they needed from racks and pallets on both sides of the aisle. The work and material flow for parts delivery to the robotic welding cells involved 16 stops, or actions, from pickup to placement in the welding robot load positions.

Today, the storage racks and pallets are gone. Now, a driverless tow tractor pulls as many as five dollies full of auto parts from the storage area to the cells, a distance of about 950 feet. Team members retrieve the parts they need from the dollies, which are positioned parallel to the cells just a few steps away, eliminating the need to cross the aisle. Once all the parts have been unloaded, the AGV returns to the storage area for more material, while another tractor with the next batch of parts arrives just when they're needed. Instead of 16 stops, there are only nine. And because the AGVs always travel the same route at the same speed, the time from pickup to arrival at the welding cells is consistent and predictable.

To get where they're going, the tow tractors follow over two miles of magnetic strip slotted into narrow troughs in the concrete floor. Their positions are tracked by RFID tags embedded in the floor.

Navigating the high-traffic body-weld department requires care and precision. The weld stations are positioned along a 300-foot "highway" with nine routes branching off and merging into it—an area known as "spaghetti junction." In addition, the tow tractors have to share the road, so to speak, with other Toyota AGVs (such as L-cart material transporters and low-profile "Mouse" tug-carts) that motor along the same magnetic guide paths. The tow tractors also cross paths with the manned vehicles that deliver partial loads and those destined for multiple drop-off sites. Drivers are required to yield to the AGVs.

To manage the movements of the automatic vehicles, TMMK's AGV implementation team worked with ICI to develop traffic-control technology that would be compatible with the guidance systems and control devices already in place for other types of AGVs. The resulting Automated Vehicle Intersection Navigational Utility (AVINU) is "the link between the AGVs and everything else that's automated," said ICI President Tim Taylor.

The wireless system communicates with the different types of AGVs, reporting each one's location, status, and performance data—information that can be viewed on any authorized computer in the facility. AVINU assigns loads to vehicles and regulates traffic at intersections; arrival at certain RFID tags triggers wireless transmission of instructions to the AGVs. The system also monitors battery status and tells the vehicles when to head over to an opportunity charger.

REACHING A BROADER AUDIENCE
Changing the way parts are delivered and reconfiguring the robotic welding cells has cut walking distances by 978 miles a year, saving five hours of walking time per shift—the equivalent of 317 work days annually, said Paul Stafford, specialist production engineering and AGV implementation lead. Furthermore, eliminating the storage pallets and flow racks opened up nearly 37 square feet of work space adjacent to each cell, freeing up space for other activities.

Because the AGVs travel the same paths at a consistent speed without so much as an inch of variation, they can safely navigate turns that would challenge human drivers—in some places, with less than six inches of clearance, according to Stafford. Congestion, collisions, sudden stops, and in-transit product damage have all been eliminated.

The labor savings have been equally impressive. The body-weld department has been able to reassign 42 people to other, more value-adding positions—including to the AGV implementation team—and nobody has been let go.

So far, the Toyota AutoGuide/AVINU project has saved TMMK more than $1 million annually, and ROI was achieved in just over one year. The payback has been substantial enough that the AGV implementation team will roll out the system elsewhere at Georgetown and will help to implement it at other Toyota auto plants.

The project foretells wider adoption of automation, not only in manufacturing but also in warehousing and distribution. In fact, AutoGuide attachments for Toyota pallet trucks and forklifts are already in the works. "I believe the automation market is limitless, although there will be challenges," Meyer said.

One of those challenges will be to convince warehouse and DC operators that automatic vehicles are not as complicated and expensive to purchase, install, and operate as they might think. That may not prove particularly difficult, however: Meyer estimates that the cost of a new, mass-produced vehicle plus the AutoGuide automation kit would be approximately one-fourth that of a custom-built traditional AGV. The fact that the AGVs are created from standard industrial vehicles and widely available, off-the-shelf components rather than proprietary controls will keep the cost down, he added.

Potential buyers will also want assurances of ready access to maintenance services for this new breed of AGVs, said Martin Boyd, vice president of product planning, marketing, and training for Toyota Material Handling U.S.A. Inc. That makes it critical to provide service for both the truck and the AGV components through the existing dealer network with its established relationships, he said.

Boyd agrees that lower-cost AGVs are poised for rapid growth. The economic downturn forced companies to look for waste, cut costs, and introduce more process efficiencies while considering how to better prepare for rapid change, he said in an interview at TMMK. Automation can help in all of those areas, and lift truck manufacturers will play a leading role in bringing it to a wider audience, he said. "We want to develop broader solutions around the customer to help them save money. We don't see automation as a competitor. We see it as an enabler."

Note: For more on this topic, read "Leave the (forklift) driving to us?"