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Delivering the Goods PUBLIC ACCESS

Roller Conveyors Handle Big and Small Loads at a the Ford Assembly Plant.

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Associate Editor

Mechanical Engineering 121(12), 70-71 (Dec 01, 1999) (2 pages) doi:10.1115/1.1999-DEC-7

Abstract

This article presents a review on two conveyors at the Ford Motor Co.’s Wayne, MI, assembly plant that use the same technology to meet two very different requirements. One system handles fully dressed, pallet-mounted engines in packages weighing up to 1600 pounds, while the other deals with pallet-mounted instrument panels having a total package weight of 80 pounds. The conveyors, supplied by Bleichert Inc. of Sterling Heights, Mich., use a roller drive mechanism that allows them to adapt to the different application requirements. Ford accomplishes the engine/chassis marriage by lifting completely dressed engines into the vehicle from below. The pallet-mounted engines are transported on a cart, called a moon buggy by Wayne plant personnel. The drive motor can be positioned anywhere along the length of the conveyor. It uses a gear reducer and timing belt to transmit power to the driveshaft. Each of the one-meter-long driveshaft sections is linked to the next one by a coupling to complete the modular drive system.

Article

Two conveyors at the Ford Motor Co.'s Wayne, Mich., assembly plant use the same technology to meet two very different requirements. One system handles fully dressed, pallet-mounted engines in packages weighing up to 1,600 pounds, while the other deals with pallet-mounted instrument panels having a total package weight of 80 pounds. The conveyors, supplied by Bleichert Inc. of Sterling Heights, Mich. , use a roller drive mechanism that allows them to adapt to the different application requirements.

"The maintenance staff at Wayne was very emphatic about what they did not want," noted Bleichert's vice president, Mike O'Brien. "What they did not want was a chain or a belt-driven conveyor in either application."

With those design constraints, Bleichert's solution was to build a system around the AL-25, a modular roller conveyor using a bevel-gear drive that requires no lubrication. The conveyor was originally designed several years ago to handle heavy power train parts, such as engine blocks and cylinder heads.

One of the major advantages of the AL-25 concept, according to Bleichert's project engineer, Paul Rice, is that the roller drive is regulated by a friction clutch with adjustable tension. "For light loads you simply reduce the clutch tension, and for heavier loads you increase it," Rice said. "That capability gives the AL-25 a tremendous application range, which we made use of in the Ford Wayne systems."

Ford accomplishes the engine/chassis marriage by lifting completely dressed engines into the vehicle from below. The pallet-mounted engines are transported on a cart, called a moon buggy by Wayne plant personnel. As the body moves along the line, the moon buggy is positioned under it on a floor-mounted chain conveyor, and then the engine is pneumatically lifted into place and installed. Sixteen moon buggies are used to install engines at a rate of about 62 cars per hour, said O'Brien.

Bleichert faced a twofold challenge. First, empty pallets, which weigh 650 pounds, must be removed from the moon buggies and returned to the engine dress area. Then, full pallets, weighing up to about 1,600 pounds, have to be placed on the moon buggies for delivery to the assembly area. During both phases of the operation, the on-board pneumatic accumulator on each moon buggy is recharged by the Bleichert equipment.

Bleichert's solution is a pair of AL-25 conveyors in an over/under configuration that is designed to conserve floor space. The installation takes up less than 300 square feet, O'Brien estimated. That makes it necessary to raise and lower the pallets during the process. The conveyor itself links loading and unloading stations designed to automatically get pallets on and off the moon buggies, plus a number of other ancillary tasks. The two operations are virtually mirror images of each other, with only the direction of transfer being changed.

Ford had been using a gantry system to load and unload the moon buggies, but this had proven less than satisfactory for a number of reasons. "The gantry was not as flexible from the standpoint of the product changes," said O'Brien. One advantage of the conveyor system is that it is not dependent on the type of product being moved. It simply moves a palletized load. "You can put different models and varieties of product on a pallet, and the handling system doesn't care. It just moves it through," he said.

The conveyor is designed with various backup components, such as redundant drives on the lift units. In case of serious repairs, Ford has a duplicate conveyor system located nearby, he added.

The moon buggies travel around a circular track in a counterclockwise direction. As each cart enters the unloading station, it is captured and located by the Bleichert automation. The buggy's table is raised to a specified height and locked in place with a pair of shot pins. The pins are necessary to ensure the precise positioning of each moon buggy entering the station for loading and unloading, said O'Brien. At the same time, a connection is made to the buggy's on-board pneumatic accumulator and it is recharged during the unloading process.

The AL-25 over/under conveying system is linked to a pair of loading/unloading stations that automatically raise and lower to maneuver engine pallets off and on a moon buggy.

Grahic Jump LocationThe AL-25 over/under conveying system is linked to a pair of loading/unloading stations that automatically raise and lower to maneuver engine pallets off and on a moon buggy.

When the moon buggy is captured and located, a cylinder extends to an open mechanical latch, which holds the pallet in position to keep it from falling off. Next, a second cylinder pushes the pallet off the cart and partly onto the AL-25 conveyor. The conveyor is then activated and the rollers pull the pallet completely off the buggy.

Once on the conveyor, the pallet is lowered approximately 24 inches to match its height with that of the lower, return leg of the conveyor system .. It is pushed off the side of the short conveyor section and onto the main line by a cylinder. The conveyor then delivers the empty pallet to the engine dressing area for reloading.

The sequence is reversed at the loading station, with the only change being the insertion of four pins under the moon buggy table as a safety measure before the 1 ,600-pound pallet is loaded. The on-board accumulator is recharged, the pallet is latched into place, and the moon buggy is sent off to meet the vehicle scheduled to receive the engine it is carrying.

In another area of the assembly line, a very similar Bleichert AL-25 conveyor delivers pallet-mounted instrument panels for installation. Here again, the over/under configuration is used to conserve floor space, and automatic handling automation is included to raise and lower full and empty pallets.

This system is different from the engine-handling setup in a couple of ways. First, the parts are much lighter. Instrument panels weigh up to 80 pounds, and the base pallets weigh 100, for a total of 180 pounds for the heaviest combination. Second, the system is designed in independent zones that permit accumulation to match the assembly line requirements.

The conveyor uses a total of 15 standard ac motors, each one running a specific section of the conveyor. "At the end of each zone is a switch that shuts down the section if it remains full for more than 15 minutes," noted Rice. "We did this to conserve energy and to minimize wear on the system while the pallets are not moving."

The delivery conveyor is also run at a slower speed than the return conveyor, Rice added. "We deliver IPs at 40 feet per minute and return empty pallets at 50 feet per minute to keep everything in balance." The quick return allows fewer pallets to be used along the 90-foot conveyor.

The conveyor is designed around a modular concept that minimizes the engineering requirements and lead time. In the AL-25, the roller drives are designed in one meter segments, with rollers spaced at 3.5 inches and up to handle various loads, depending on application.

Each roller is operated by a glass-reinforced polyurethane bevel gear, which is powered by a modular driveshaft running the full length of the conveyor. Torque from the driveshaft is transmitted to the bevel gear through a spring loaded clutch. Clutch friction is adjustable in seven increments to match the load. The clutch is adjusted during the conveyor's installation and usually doesn't require any further modifications, said 'Q'Brien.

The drive motor can be positioned anywhere along the length of the conveyor. It uses a gear reducer and timing belt to transmit power to •the driveshaft. Each of the one meter-long driveshaft sections is linked to the next one by a coupling to complete the modular drive system.

"Because the drive is completely modular, it is very easy to set up an AL-25 in a zoned configuration, as the company did for the instrument panel conveyor at Wayne," said O'Brien. "All you have to do is leave out the coupling and add a motor for each zone," he said.

Copyright © 1999 by ASME
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