In Whitby, Ontario, Johnson Controls, Inc. (JCI) installed a system of 99 automatic guided vehicles (AGVs) to synchronize the flow of instrument panels through its facility with the assembly schedule at nearby GM plants (Jervis B. Webb Co., 248-553-1220).

Guided by magnetic tape on the floor that can be easily reconfigured when processes change, the AGVs, which resemble carts and are often called just that at Johnson, provide a flexible manufacturing platform. "We can change station locations, the number of stations, and the travel path of the carts within a matter of hours and not weeks or months," says Stephen Nagy, group manager, advanced materials and process engineering. "The costs to do so are minimal, and our ability to maximize labor efficiency is greatly enhanced."

The vehicles act as a mobile assembly line. JCI's enterprise system receives a broadcast from General Motors of the parts that must be built in sequence to match up with cars coming down the assembly line.

The broadcast is also sent to a centralized cart management system (CMS), which controls all of the vehicles from one location. Based on the parts to be built, the CMS determines what vehicle the panel will be built on and the sequences for assembly.

That information is used to create a bar code that is applied to a vehicle as it starts down the line. An assembly backbone, which holds the part in place as it's assembled, is also added to the vehicle. "We kept the on-board intelligence to a bare minimum because we don't want the carts making autonomous decisions," Nagy says. "All the cart knows is to stop, go, and follow the line to the left or the right."

The CMS directs a vehicle to the correct station for that assembly. If a vehicle stops at a specific station, an operator knows to install a part. The bar code label is scanned as a check against error.

When the assembly is done, the vehicle is directed to the shipping area, where an operator unloads the cockpit assembly to a shipping pallet. After an assembly backbone for the next part is installed, the vehicle is ready for its next assignment.

"This is a very flexible manufacturing method, one that's easy to make process improvements," says Nagy. "The one statement that really comes up is that the carts allow us to make significant manufacturing changes over a weekend."