Site: BMW Manufacturing Corporation

Auto Manufacturer Storeroom Expands Internally With VLMs To Support Almost Doubling of ManufacturingCapacity

Application: Spare parts storage for automobile manufacturing

Equipment: Five Shuttle™ Vertical Lift Modules with fire suppression system

Summary: Storeroom capacity increase to handle plant expansion and additional production lines

Resounding popularity and sales of its new models, compelled BMW Manufacturing Corp. to enlarge its plant near Spartanburg, S.C., from 1.2 to 2.1 million square feet. The 900,000 square foot addition provides added production capacity plus a more flexible manufacturing base to accommodate a wider range of models and mixes of model volumes.

The impetus for BMW’s plant expansion was the introduction of the X5 sports activity vehicle (SAV) in September 1999. The X5 is the first luxury SAV, combining the powerful acceleration and exceptional handling of a car with advanced traction technologies and all-wheel drive. The vehicle is the first BMW to be launched first in the U.S., and its development and manufacture was the first truly global BMW project.

“Even with the dramatic increase in production capacity and manufacturing flexibility, the plant’s existing 7500 square foot storeroom housing spare parts for manufacturing equipment was not allotted any more space,” commented Tony Brannon, Coordinator, Central Operations Support.

“Although drawer cabinets, a pallet stacker, and shelving were already nearly full, the room’s vertical cube was largely untouched. Making more efficient use of this cube would allow parts for new machinery to be accepted.”

Vertical Lift Modules Carry the Load
To reach into the storeroom’s vertical cube, BMW installed five Remstar Shuttle 250NT Vertical Lift Modules side-by-side. The Shuttle is a standalone, modular, enclosed system of vertically arranged storage trays, a workstation-type extraction platform, and computerized pushbutton controls for part retrieval. It stores and retrieves a variety of component containers on specially designed trays and delivers them to an ergonomically positioned workstation. The Shuttle has a fast vertical travel speed of 212 feet per minute.

Three of the Shuttle units are 26 feet tall, while two are only 22 feet because of interfering roof beams. To help equalize storage capacity per VLM, the shorter units are wider — with wider internal trays (shelves) — to compensate. These units feature 69 trays each 72”W x 32”D. The taller, narrower VLMs have 55 trays each 49”W x 32”D.

Improved space utilization is a key advantage of vertical storage and retrieval systems. Depending on usable building interior heights, 75 percent and more of a conventional storage system’s occupied floor space can be recovered. The small unit footprint makes vertical storage and retrieval systems especially suitable for point-of-use storage, allowing more floor space to be assigned to value-added operations such as manufacturing and assembly.

“The five VLMs replaced a length of six foot high, 35-foot long shelving in a corner of the storeroom,” Brannon added. “The modules displaced little existing storage, however, because relatively few spares are held on shelves. The five VLMs, including a 42-inch aisle, consume only 363 square feet of floor space.”

Storage Efficiency Gain
To calculate the number of VLMs required, BMW performed an analysis comparing them to standard 30”W x 30”D x 60”H drawer cabinets. The comparison was made against cabinet storage because the VLMs were slated to contain the same types of spares as maintained in the storeroom’s existing cabinets, plus some larger items such as VFD drives.

The evaluation demonstrated that each VLM could hold the contents of approximately nine cabinets. Including necessary 42-inch aisles, 45 equivalent cabinets would require about 800 square feet of floor space - twice the space required for the VLMs. The increase in storage efficiency for the VLMs reflects not only the use of the vertical cube, but also the reduced aisle space required per square foot of tray/drawer space as well as the VLMs’ design to effect higher storage density.

“The Remstar Shuttle Vertical Lift Modules automatically minimize tray-to-tray vertical spacing within the stacks each time the tallest item on a tray is removed and the tray is returned to the stack,” Brannon said. “In fact, the auto-optimization (CubeStar™) feature was the single most important factor in the selection of these particular VLMs. Drawer-to-drawer spacing in cabinets is not readily adjustable, of course.”

The dollar value of floor space consumed by both VLMs and cabinets was also calculated to justify the investment. Storeroom floor space carries the same value as production floor space, which is assigned the highest figure at BMW’s South Carolina site. Consequently, the economic incentive for extending into the vertical cube is very high.

As a result of the storage space gained by installing the new vertical lift modules, the storeroom was able to easily accept spares for all of the plant’s new equipment. Should more space be required in the future, additional VLMs can be quickly added. The five VLMs were installed while the plant was operating and without the storeroom being shut down. Spares on the replaced shelving were temporarily consolidated on other shelves. To meet a unique application requirement, the VLMs are fitted with internal sprinklers mandated by the local fire marshal.

Fast Retrieval
The innovative vertical storage units provide enclosed protection for the densely-packed trays of parts. When a part is called for by a BMW storeroom associate, the correct tray is automatically lowered by an internal elevator to a waist-high extraction platform, where it is advanced out toward the associate for easy part removal (or putaway). Tray-to-tray retrieval times for the VLMs at BMW range from 30 to 32 seconds. Load capacity per tray is 590 lbs, and balancing the load is unnecessary because the trays are chain-driven from both ends.

“Stored on the trays are items such as circuit breakers, pushbuttons, small hydraulic and pneumatic valves and cylinders, welding gun components, and air wrenches,” Brannon reported. “Most are bolt-on parts supplied by machinery OEMs located all over the world. Of the storeroom’s 14,500 part numbers, 2,600 are presently carried in the VLMs.”

Parts as tall as 29.5 inches are accommodated; minimum tray-to-tray stack spacing is 4 inches. BMW stores larger parts free on the trays, while smaller parts are consolidated in blue plastic containers. Heavy items with moving parts are often laid on rubber matting to minimize bearing or O-ring deformation from building vibrations.

“Before and after each tray extraction, a light-curtain sweeps the tray looking for parts extending beyond the tray’s edges and also for parts taller than the last height detected and remembered by the VLM for that tray,” Brannon said.

“The later information helpfully points out unclosed carton flaps, plastic bags sticking up, and other storage irregularities. The curtain also determines the stacking density to be selected when the tray is returned to the stack.”

“BMW further maximizes storage density by minimizing part storage heights and by placing parts of similar height on the same tray,” Brannon said. “The company can adjust both the horizontal and vertical extraction speeds of each tray individually to reduce forces generated by heavy parts.”