New systems drive Jeep throughput to record level
Redesigned Grand Cherokees roll off the line 10% faster than in '98 model year with new process and conveyor systems.
By Tom Feare -- Modern Materials Handling, 6/1/1999
Recently, the long-running American love affair with the auto has turned into a keen desire to drive a sport utility vehicle. Among SUVs, U.S. buyers have selected the Jeep Grand Cherokee as one of their top choices.With so popular a vehicle, Jeep management decided to increase production for the '99 model year.
Capacity would rise 10% at the Jefferson North Assembly Plant in Detroit. With nearly 4,000 assembly line hourly employees on 3 shifts per day, the plant would strive to build 1,336 Grand Cherokees a day, up from 1,214 for the '98 model year.
Reaching this increased production goal had to occur within the same time frame that another objective had to be met: the Grand Cherokee would undergo a major makeover for the '99 model year.
This model redesign truly was a significant step, adding further complexity to manufacturing challenges, notes Mike Colburn, plant engineering manager at the Jefferson North facility of DaimlerChrysler. For the '99 model year vehicle, there's just one bag full of items, 165 parts in all and mostly fasteners, unchanged from the '98 Grand Cherokee.
To meet the greater capacity and model redesign goals, Jeep has added 847,000 sq ft to the plant and miles of power-and-free conveyor.
As Modern Materials Handling was going to press with this issue, Jeep's Grand Cherokee production team already had racked up a record of 100 straight days of meeting the higher build number of 1,336 vehicles a day and was still counting.
Thousands of man hours
Changes in the '99 Grand Cherokee's parts led to changes in work cells and process equipment as well as in the materials handling systems transporting work-in-process between all of the assembly steps, as Colburn points out.
New conveyor systems had to be installed and integrated with the new process equipment by DaimlerChrysler's principal conveyor manufacturer and supplier at this Detroit plant (Dearborn Mid-West Conveyor, DMW).
Completing changeover consumed over 400,000 man hours for work supervised by DMW. The Jeep plant's trim shop changes alone required the services of more than 1,100 people working 24 hours per day, 7 days per week.
This change-over was unique, moreover, says David Standen, the DaimlerChrysler senior manager in charge of launch coordination. "We added 847,000 sq ft of plant in two-and-a-half years without ever missing a day of production."
Plenty of power-and-free
Auto assembly in the U.S. still relies heavily upon conveyor transport as it has since very early in this century. This Jeep facility is no exception. Power-and-free conveyor-either inverted power-and-free or overhead power-and-free-and of several sizes-is the predominant materials handling technology moving work-in-process at this plant.
More than 10 miles of power-and-free conveyor equipment run through Jefferson North's two body shops and trim facility. Before any '99 Jeep Grand Cherokee starts recording miles on its odometer, it completes a ride of a day-and-a-half's duration over these power-and-free systems and some other conveyor types as well.
There's a very good reason for choosing power-and-free technology, as Colburn explains: "We can buffer our processes more on the new line than we did on the old line with accumulation zones. The power-and-free system provides this capability for accumulation and storage. This design feature protects us from having excessive downtime. And it improves our throughput."
Transfers between overhead and inverted power-and-free systems are accomplished by means of equipment such as a high-lift transfer mechanism or by a fork transfer method (photo, preceding page).
Powered roller, chain-on-edge, and flat top conveyor systems are to be seen in shorter stretches than the power-and-free conveyor lengths, and round out conveyorized handling at the plant (see System at a glance).
Planning a launch
Before a new, major launch of a model, an automaker goes through years of advance work and planning, as Colburn observes. One aim is not to affect prior production. Nor does the plant want to get off to a slow start on new assembly processes for a makeover.
Typically, however, an automaker has only a summertime plant shutdown period of several weeks to make the changes in process equipment and handling systems that go into a launch.
Instead, in switching over to '99 Grand Cherokee production, DaimlerChrysler chose to build a new South Body Shop at the plant.
At this body shop, Jeep pilot operations for the redesigned '99 vehicle, or WJ model, could be conducted for some 7 months or so, prior to shutdown of production on the prior ZJ model late in May 1998.
"Working the pilot in the new body shop gave us a tremendous lead time on our WJ launch," says Colburn. "Our new process equipment systems and conveyors were all well tried out in advance of our three-week changeover period.''
"Risk was minimized," declares Frank LaSota, materials manager. "On June 1st last year we knew how the South Body Shop would run and we were ready to go a week later and capable of filling the assembly line."
Jeep also constructed a major addition to its Trim/Chassis/Final assembly area. The North Body Shop's existing operations remain, essentially as they were before. But selected manual processes and their associated conveyor systems had to be incorporated into the new, overall layout. And everything had to be integrated into a smooth flow of work-in-process vehicles moving to work cells.
Manufacturing strategy
The manufacturing strategy for process and materials handling systems at the DaimlerChrysler plant, says launch coordinator Standen, involves a number of steps:
- To improve production operations with the latest and/or best technology where feasible,
- To rely even more on just-in-time supplies to assembly,
- To eliminate or reduce waste in processing and handling, and
- To improve ergonomics.
Achieving these goals has meant adding more robotics in a few plant areas and increasing JIT deliveries to workstations. "A year ago," recalls Standen, "you couldn't see down some aisles" due to parts piled up at workstations.
Through more efficient JIT deliveries and line-side supply, aisles now are more open. Morale has improved, Standen declares. "Employees don't feel like they're working in a closed-in cave," he suggests.
Carton flow racking at workstations improves the picking of small parts prior to use in assembly, and these racks are readily replenished. At various steps in assembly, DaimlerChrysler has taken other measures to eliminate stooping and bending motions by employees and enhance ergonomics.
This Jeep plant also relies heavily upon JIT suppliers to deliver three kinds of components to the trim shop which are necessary to complete a Grand Cherokee: seats, fascia, and instrument panels.
Because Jefferson North assembles on an in-sequence basis, as materials manager LaSota explains, these parts are supplied not only just-in-time, but also in the build schedule or order sequence that they'll go to assembly to be matched to a specific vehicle by color, fabric, or some other specifying feature. EDI (electronic data interchange) transactions between plant and supplier will ensure information on sequence is correctly communicated.
Seats, for example, will arrive in the supplier's delivery truck as a "slug" to be unloaded automatically. The truck trailer's bed includes roller conveyor. Upon arrival, the truck driver "plugs into" the dock system to begin the unloading process. Seats on special pallets roll off the truck and into the plant.
In the case of fascia JIT deliveries, a major process change for fascia installation for WJ production resulted in a slight change in materials handling for these parts. Instead of racks, fascia now arrive on pallets, as LaSota explains.
Millenium model launch
Methods for vehicle production and related materials handling procedures at this plant hardly are static. Continuous improvement is a goal, and one which involves hourly employees along with managers.
"Fourteen managers can't make all the decisions," launch coordinator Standen declares.
During the months of the countdown to the '99 launch as many as 120 hourly employees were involved at any one time with a corporate and vendor design team directed at problem solving-maintenance workers, millwrights, pipefitters, and others joined the group.
DaimlerChrysler also continually simulates its operations on computer software to find ways to improve processes and materials handling. During the next Grand Cherokee plant shutdown, Colburn says, the findings from team suggestions and simulation will result in several changes to conveyor systems on the main line and at a door assembly step.
System at a glance
DaimlerChrysler Corp.
Jeep Jefferson North Assembly Plant,
Detroit, Mich.
Plant engineering manager: Mike Colburn
Project: Plant redesign for Jeep Grand Cherokee '99 model year assembly
Project cost: $750 million including 847,000 sq ft expansion
Plant size: 2.6 million sq ft
Hourly employees: 3,994, working on 3 shifts/day
Production rate: 1,336 vehicles per day
Conveyor systems: Dearborn Mid-West Conveyor, 734-288-4400
Conveyor types, lengths: Inverted power-and-free, 45,138 ft; overhead power-and-free, 12,434 ft; flat top, 1680 ft; inverted axle/chain-on-edge, 665 ft
Assembly carrier fixtures: 1,740
Axle insertion process (moon buggy) vehicles: Platform, Kuka, 810-795-2000; Lifts, Handling Specialty, 716-694-6333
Overhead and workstation cranes: Unified Industries, 517-546-3220
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