Engine production hums

Diesel engines for Hummer and Humvee vehicles move by towline systems for a synchronous flow, keeping high-quality production simple, but efficient.

By Tom Feare, Senior Editor -- Modern Materials Handling, 1/1/2001

Feel like making a statement behind the wheel? Try driving a Hummer in rush hour traffic. You'll always have the right of way. Or so a brochure brags.

You also could take "the world's most serious 4 x 4 vehicle" off road. There you can make this 4-wheel drive vehicle perform much like its military cousin, the HMMWV (pronounced Humvee) or "high mobility multi-purpose wheeled vehicle."

Now these 4 x 4s aren't for everyone. In fact, there have only been 150,000 of these high-quality, high-performance vehicles made since 1985 for military purposes. And such low volume requirements impact not only Humvee and Hummer final assembly, but production of key vehicle subassemblies as well. In turn, that affects the materials handling systems necessary for competitive manufacturing.

A low-tech, high-tech mix

AM General Corporation, manufacturer of the Humvee and Hummer, made its own statement not long ago about these vehicles and building engines for them. In 1999 it formed a wholly owned subsidiary, General Engine Products, Inc., to produce diesel power plants for the 4 x 4s. Last year GEP finished construction of a new engine manufacturing plant in Franklin, Ohio. The plant began operating in July 2000, and will reach full capacity early this year for producing V-8, 6.5-liter diesel engines.

The 80,000 sq ft plant combines mechanized materials handling along its assembly lines with high-technology engine production and test equipment in its work cells.

"Our handling and manufacturing systems are an appropriate mesh of lower tech and higher tech," as Carter Hamilton, plant manager, says. Appropriate technologies have been matched to GEP's needs to build quality engines.

Synchronous movement of engines through progressive assembly by in-floor, chain-driven towline conveyors is one lower-tech solution to the plant's needs, as Hamilton explains. The engines move from work cell to work cell by riding on carts pulled by the towlines. The carts were custom designed and engineered for GEP's purposes.

"Keep it simple, but efficient," says Wilbur Boggs, project manager, manufacturing engineering for AM General. This philosophy figured prominently in his approach to designing and selecting the materials handling systems supporting assembly at GEP. Cost effectiveness of the towlines was also a key concern, he adds. And good ergonomics for the operators working on engines riding aboard the custom carts was a vital concern as well.

In contrast, within certain work cells on GEP's lines there are some very high tech systems, including automation. These technologies are specific to diesel engine manufacture, such as automated systems for torque control and computerized equipment for performing various engine assembly testing and checking operations, as Hamilton explains. Diesel engines need to be manufactured to very exacting tolerances between their component parts and to high quality standards for longtime performance and extended durability.

Synchronous and simple

The Franklin plant has two towlines (Rhodes Systems Worldwide, 812-246-5200, www.rhodesworldwide.com ) running now in a synchronous mode.

"Synchronous operation keeps it simple," says Hamilton, "and enables us to achieve the greatest uptime." Even so, he notes that the GEP plant "has the flexibility to run the towlines synchronous or non-synchronous."

Each of these lines has the built-in versatility to be switched over to non-synchronous assembly should that approach ever be necessary. Running in this mode would permit more accumulation and more delays of carts with work-in-process engines aboard them without shutting down the towlines.

GEP builds both turbo-charged and non-turbo diesels at Franklin. In all there are 19 variations of the basic engine.

Engine production begins on what GEP calls its short block towline (see layout). Here assembly progresses through 21 work cells. At the end of this line, the diesel engines reach a stage where (1) they're ready to be shipped out as service parts or (2) are destined for final assembly and for "dressing out" at the plant's final trim area with add-on external components. The latter will become original equipment engines in new vehicles.

Engines in this second category are rolled on their carts from the short block line over to the final assembly towline. Before moving down this line, each short block engine will be loaded onto a customized pedestal-style cart with a special fixture, or engine "saddle" to hold it.

Next, the engines proceed through 16 more work cells where they undergo final assembly procedures. Then they move to hot test cells where they will be fired up for the first time and put through their paces until they meet all standards.

Finally, tested and approved engines move by towline from the hot test area to the final trim area for some "dressing out" steps. These finished engines are unloaded from their transport carts and staged in special racks for shipping to AM General's vehicle assembly plant.

Ergonomics emphasized

Throughout all the assembly steps in the 37 work cells of the two towlines, ergonomics of engine production has been emphasized. Transport carts were prototyped at the plant, says Hamilton, and were designed by engineers there. Ergonomic cart design "facilitates ease of assembly," he adds, and fosters high quality production while maintaining worker health and avoiding repetitive injuries.

The customized carts that carry the engines "are ergonomically correct for our operators," says Boggs, moreover. Operators can move around the individual engine on a cart as needed to perform assembly. Or the engines can be rotated 360 deg in either direction on both types of carts used at GEP.

On the short block line the carts feature rotation axially around the engine crankshaft. Operators readily have access to five of the six sides or planes of an engine without rotating it, however. On the final assembly towline, engines on carts can be rotated horizontally as needed for full access by operators.

Accident prevention stressed

Safety features have been designed into GEP's towline systems. The in-floor models were chosen over above-floor towline, says Hamilton, because of safety concerns. "The towlines are smooth to the floor," notes Boggs. "There are no trip points."

Accident prevention has been stressed as well in further equipping the towlines with safety features. Toe guards, for example, have been fitted over the wheels of all transport carts. The guards were purchased by the plant at extra cost, explains Hamilton.

With an engine aboard a cart, the combination weighs about 1,200 lb, he notes. "But we never have to worry about a cart rolling over an operator's foot," Boggs adds, because of the guards.

Ramping up to full capacity

With the plant running at about 70% of capacity late last year, Hamilton says it "has had virtually 100% uptime." The towlines have required very little maintenance, he adds, "and I am very happy with that."

Soon, Hamilton anticipates the plant will be building its designed capacity of 100 engines per day on a single-shift operation. One goal targeted for this year is for GEP to maintain only 2.5 days of supply–from incoming components to finished engines–at the Franklin facility.

Should future demand climb or a greater variety of engines need to be built, this plant already has the flexibility engineered into its materials handling systems to accommodate growth and to adapt to new ways of doing business, moreover.

Manufacturer Profile

AM General subsidiary, General Engine Products Franklin, Ohio

FACILITY facts:

Products manufactured: V-8 6.5 liter diesel engines for Humvee and Hummer vehicles

Manufacturing capacity: 100 engines per day

Facility size: 80,000 sq ft

Employees: About 100

Towline conveyor systems:

Rhodes Systems Worldwide, 812-246-5200, www.rhodesworldwide.com