Breaking the mold

At CAMI Automotive, automatic guided carts and a wireless call button-enabled handling system radically changed parts delivery to the assembly line.

By Bob Trebilcock, Editor at Large -- Modern Materials Handling, 1/1/2007

Sometimes a break with the past is critical to future success. And that is exactly what happened to several key materials handling processes that support the assembly line at CAMI Automotive's 1.64-million-square-foot assembly plant, two hours north of Detroit in Ingersoll, Ontario, Canada.

"We broke the mold of how we had done business for 15 years," says Larry MacAdam, a materials industrial engineer at CAMI.

The result is an entirely new system that optimizes the delivery of parts from a separate but nearby crossdock facility to the receiving dock and the assembly line in Ingersoll. The 18-year-old plant produces the Chevrolet Equinox, Pontiac Torrent and Suzuki XL-7. CAMI is a joint venture between General Motors and Suzuki Automotive.

One of the key elements is a system of automatic guided carts—a simplified version of an automatic guided vehicle —that delivers sequenced plastic bumper coverings to the line.

In addition, the whole delivery process is enabled by wireless call buttons. These communicate everything from when parts need to be replenished at the line to when the dock doors are free for a yard driver to remove and stage the next trailer.

Finally, all bins and racks are designed with wheels or are put up on fabricated wheeled dollies that allow them to be delivered to the line with tuggers. The delivery of parts by tugger allows for five parts to be delivered to the line at once.

"With this system, we can operate the plant using just-in-time, just-in-sequence principles to deliver 10,000 totes, bins and racks of parts daily while holding very little inventory," says MacAdam. In fact, the new delivery system allows CAMI to deliver parts for 190,000 vehicles a year with the same number of team members once used to deliver parts for 50,000 vehicles.

"The plant was designed with very little space for parts," says MacAdam. "We have a very small stock area in the plant, and we're often doing a one-for-one exchange of bins or racks at the line."

For 15 years, that was managed with a look-and-see delivery system.

"We had to visually look at part levels at the line, run back to the stock area and deliver a new rack or bin before the operators ran out of parts. That worked about 90% of the time. When it didn't work, we would impact production," MacAdam explains. "Because we have very little space for storage, we have always struggled with having parts staged in a predictable location for when we needed them."

A model changeover and a higher line speed necessitated a new parts delivery system to the line. Under plant manager Peggy Green and assistant manager George Randall, ideas surfaced as they re-evaluated the way the plant did business. The new system was designed to make the line delivery more predictable by automating and coordinating the flow of materials electronically instead of visually.

The process begins when a demand signal is sent from the assembly plant to vendors who sequence parts at their location for just-in-time, just-in-sequence delivery directly to the plant. That same signal is also sent to CAMI's crossdock center a few miles from the plant. The center primarily handles non-sequenced parts delivered there by vendors in bulk but expected at the plant in a given delivery window.

The plant receives both sequenced and non-sequenced parts. Many parts, like seats, engines and instrument panels, are sequenced at the vendor to correspond to specific vehicles coming down the line. These parts are unloaded and delivered directly from a trailer to the production line using automation. A small number of non-sequenced parts, like weather stripping for windows, are delivered directly to the plant in bulk.

The crossdock center handles most of the non-sequenced parts. The center receives bulk deliveries and breaks them down into mixed deliveries at regular times, usually every two hours. The majority of the parts move through the crossdock center in about 12 hours.

As the crossdock loads the trailers, they are moved to the plant and staged in pre-designated parking spots prior to being delivered to one of the numerous docks at the plant. Each yard driver's tractor is outfitted with an onboard terminal. When a trailer is released, a wireless signal is sent to the yard driver that the empty trailer is ready to go, and the next scheduled trailer must be staged to the dock.

Inside the plant, all totes, bins and racks are put on wheels. "Instead of a fork truck moving two or three units at a time, we deliver them to the line with a tugger that pulls multiple units," says MacAdam.

Totes, bins and racks are delivered from the storage area to a pick-up area by lift truck. After dropping off parts, lift truck operators return any empty totes, bins or racks to the shipping dock, where they're loaded onto the next truck returning to the crossdock center.

Meanwhile, tuggers deliver the inventory to the line. And like the trailers in the yard, bins, totes and racks are equipped with a call button.

When the inventory of parts at the line reaches a pre-determined level, the operator pushes the call button; that, in turn, sends an electronic signal that triggers the replenishment of parts at the line and stock area.

"The system was designed to not only locate parts but to act as a communication system," says MacAdam. "We have created a 'virtual' button on wireless terminals allowing an operator to call for assistance or put up a flag warning about a low stock level."

Most parts are sequenced prior to arriving at the assembly plant. However, fascia—the plastic covering for the front and rear bumpers—are sequenced in house.

"The fascias are bulky and they can be easily damaged," says MacAdam. "That made it too expensive to sequence them off site." Sequencing them in house, however, required a separate handling system for parts delivery. The initial design called for an overhead conveyor system, which was based on what had been seen in the fall of 2004 at another plant.

In January 2005, before the purchase of the conveyor system was finalized, plant management saw a demonstration of the automatic guided carts at a materials handling show. "They were sold on the concept at the show," says MacAdam. "Within a fairly short time, we had developed a complete system with 12 carts, which was approved by the CAMI executive team over the overhead conveyor proposal."

Uptime was the primary advantage of using automatic carts. "Conveyor systems are very reliable, but even a reliable system fails now and then," says MacAdam. "If that happens, you'll end up with 60 vehicles worth of product on a conveyor overhead and you have to shut down the line."

On the other hand, if one of the carts goes down, another can pick up the slack. What's more, if vehicle designs change requiring a change in the manufacturing line, a lot of work then goes into reconfiguring an overhead conveyor system. "With the carts, all we have to do is prep the floor and put down some magnetic tape to reconfigure the path," MacAdam says. "We can do that over a weekend or a holiday shut down."

The combination of automatic guided carts and real-time communication has transformed the way the CAMI plant makes vehicles. "We may be 18 years old," says MacAdam, "but with the way we deliver parts, and the inventive ways we are using these new systems, we're considered one of the new plants."