Delivering for Delphi

Automatic guided vehicles work around the clock moving 1,800 totes per day of finished goods at this automotive parts maker's new plant.

By -- Modern Materials Handling, 12/1/2000

It's not necessary to consult an oracle to learn great insights at this Delphi.

After visiting the new Delphi Automotive Systems plant in Cortland, Ohio, the wisdom is readily evident to its use of an automatic guided vehicle system (AGVS). In fact, it comes down to one guiding light: Automate whenever it's economically justifiable. That precept is fundamental to the materials handling strategy in place, explains James Bousfield, senior engineer, special projects.

The payback from this AGV system should be reached in just a year from full operation, says Rick Ames, general supervisor, manufacturing. "This system allows us to capitalize on our greatest asset-our hourly work force, and what they do best: Mold world-class plastic components."

For years to come, moreover, the system also should deliver very significant ergonomic benefits to workers-even if future gains in fewer injuries, less back strain from less manual handling are likely to be largely unquantifiable.

Finally, for plant managers who must inevitably cope with future change, "this is a very user-friendly system," Bousfield adds, noting its built-in flexibility for alterations to the guidance path on an as needed basis.

This six-vehicle AGVS (Frog Navigation Systems, 248-370-8950, www.frog.nl ) is a sophisticated transportation and handling system. The vehicles' task is to transport and handle small totes and corrugated boxes for the manufacturing process. They also eliminate almost all manual handling of totes and containers, fostering better ergonomics.

"The work the AGVs perform is key to helping us make this facility competitive," says Ames. "The AGVs enable us to better utilize our operators. And we've been able to right-size our containers and standard-part packs."

Each AGV, which navigates from point to point over a grid of magnets in the floor, is custom fitted to interface with the pickup/delivery (P/D) stations at the facility's 120 plastic injection molding machines.

Atop each AGV are three small belt conveyors designed to handle small totes and boxes. The conveyors are fixed at a right angle to the direction of AGV travel; the conveyors also can load/unload a tote or box from either side of the vehicle. Filled containers weigh 20 lbs. or less.

Together, the system's six AGVs are expected to handle a total of some 3,600 totes or boxes-1,800 empties going to a molding machine and 1,800 filled containers with finished goods-each day during a 24 hour, two-shift operation. Three rotating crews, with each crew working a 12 hr shift, manage the molding machines.

A big investment in the future

Delphi has invested some $43 million, including nearly $30 million for molding machines, in this 145,000 sq. ft. plant. Known as Delphi's plant 45, it manufactures a variety of small plastic parts. Some parts are made for internal use in other Delphi products. Some are manufactured for what the company hopes will be a growing list of external customers, perhaps 100 or so outside firms eventually.

When fully operational a short time from now, plant 45 is expected to process 10 million lbs. of plastics a year and produce 1 billion pieces or parts annually.

Each molding machine operator in the plant oversees 15 machines and their operations in one of the facility's eight work cells.

"Because the AGV system automatically handles and moves totes and boxes, empty or filled, the machine operator can focus his or her time and effort on the molding machine and the quality of products it makes, rather than on parts handling," says Greg Pachol, general supervisor, manufacturing systems and facility development engineering.

"Normally, best manual handling would be our choice," Pachol continues. "But, in this case, automation was clearly the better way to go."

Selecting the system

But what type of automation would be appropriate? The Delphi project team examined different handling methods for tote/box movement at plant 45. And in a life-cycle system analysis, the team studied transaction costs per tote/box handled at a molding machine.

The team found that an AGVS was more than twice as cost effective as the next best, partially manual method: An operator using a tugger vehicle transporting totes/boxes, Bousfield says. Lift truck delivery and pickup at work cells also was considered to be more expensive than an AGVS. Floor-mounted and overhead conveying technologies were rejected by the team as being too inflexible to adapt to future changes on the shop floor.

Even though, in this planning process, an AGVS readily appeared to be the handling method of choice, selecting the final system and its guidance technology took some effort. Bousfield sent out an RFQ (request for quote) document with Delphi's specs and concepts to 14 possible vendors. Ten responded, and the field was narrowed to four finalists.

Bousfield wanted maximum flexibility when it came to the AGV path. Several wireless technologies were evaluated.

The system selected uses a grid of magnets embedded into the floor (see sidebar below) as vehicle position references. The AGVS's control system then uses radioed commands and responses between a central control station and the individual AGVs for sending and acting on specific routing instructions. These commands direct each vehicle to individual work cells and molding machines on the plant floor. Positional accuracy, says Bousfield, is within 1/16th in.

"Flexibility and adaptability were major points that sold us on this AGVS," says Bousfield, moreover.

The anticipated advantages were seen soon after the initial AGVS installation. Bousfield tells how the plant team had to slightly extend the area over which the AGVs operate. But changing the guidance array of magnets was a simple and quick exercise: "Within an hour we were able to embed and add about 100 magnets into the system's grid array," he explains.

Similarly, changes in the specific routings of the AGVs to molding machine work cells can be readily made, as Larry Beck, senior electrical engineer, explains. "The AGV control system is very user friendly. Altering the paths the AGVs can take over the plant floor is as easy as changing a CAD (computer aided design) layout on a computer monitor. Working on screen we also can vary system parameters in as short a time as 1 or 2 minutes and do so without changing program logic."

The AGV controller receives its instructions on the specific jobs that its vehicles will tackle from a computerized, in-plant scheduling system for the molding machines.

Keeping it simple

Simplicity in system design was one of the rules in the materials handling strategy that the AGVS project team followed prior to installation. "Make layout and system changes, taking out non-value-added activities wherever possible," as Bousfield says.

"The AGV in our system is blind to what it carries," for example. "That is one of the simplifications we made in this system," he explains.

Similarly, by bar code labeling the tote or carton at the molding machine with the specific identification of the parts going into the container, he adds, "we lower greatly the chances of mislabeling the container."

The AGV supplier also simulated on a computer model the operations of the system before finalizing it, thereby taking out some guesswork. Meantime, Delphi simulated job content within the eight work cells on another model to establish procedures.

Ramping up to full operation

AGVs have been running on the plant floor since the end of March. Meantime, the plant has gradually phased in operations of more work cells to a complete complement of eight cells. Full production from all 120 molding machines on a 24 hour operation is imminent.

Initially, full production was expected to require handling slightly more than 1,000 totes or boxes of finished goods each day. But as the project team has gained experience with the machines, that output level has now increased to a maximum of 1,800 filled totes or boxes daily. With a planned 80% utilization rate for the AGVs (and additional time allotted for recharging their batteries) it's been necessary to add a fifth and sixth AGV to what was originally planned as a four-vehicle system.

Manufacturer Profile

Delphi Automotive Systems
Packard Electric Division Plant 45, Cortland, Ohio

FACILITY FACTS:

Shop floor: 145,000 sq. ft.

Employees: Approximately 100

Products produced: Plastic parts from injection molding machines

Output:1 billion pieces/year; 10 million lbs. of plastic parts annually

Handling throughput: 1,800 totes or boxes of finished goods handled daily

AUTOMATIC GUIDED VEHICLE SYSTEM:
Frog Navigation Systems, 248-370-8950, www.frog.nl

TOTES:
Buckhorn, 800-543-4454, www.buckhorninc.com

BAR CODE LABEL PRINTERS:
Zebra Technologies, 800-423-0422, www.zebra.com

Following both American, British rules of the road

The six automatic guided vehicles (AGVs) at Delphi's plant 45 need to be bicultural in their driving habits. Depending upon the handling step they're performing, the AGVs run on either the left or right side of the "road."

The AGVs are designed so that the three roller conveyors atop them can load/unload from either side of a vehicle, as Jim Bousfield, senior engineer, special projects, explains.

At times the AGVs drive on the right as they do within the plant's aisles. At other times, the rules of the road shift to British style: The AGVs drive on the left when they are moving in each of eight work cell aisles.

Moving on the left, an AGV can drop off an empty tote or box at a molding machine pickup/delivery (P/D) stand at the left empty container location. Then the AGV indexes forward to the full container position at the P/D stand. Here it transfers the full container to the just-vacated container location. When the AGV has serviced three machines, it then travels to a finished goods drop-off station. At times of low manufacturing system volumes, the AGV may make a round trip with only one or two containers.

Benefits at a glance

Delphi's automatic guided vehicle system:

• Automates tote/box transport and handling cost effectively