Saturday, January 20, 2007

INTRODUCTION TO HORIZONTAL CAROUSEL

If the Vertical Carousel System’s concept is similar to a Ferris wheel, then a horizontal carousel’s concept would be like a Merry-Go-Round. A horizontal carousel can be described as a series of bins that are linked together in a continuous chain and mounted on an elongated oval track. When it is activated, the bins revolve, bringing the desired bin to the operator.

The operator who is positioned at the end of the oval, picks from several carousels, working in a workstation or pod. These carousels are almost always direct by a PC, which stores the part’s location and frequently the quantity. The computer sorts batched orders by location and commonality to minimize carousel rotation time and to eliminate duplication of bin stops. It also activates a light display which shows location and quantity.

By moving the shelf to the picker, horizontal carousels almost eliminate the picking aisle. The only aisle needed is the equivalent of a cross aisle in a conventional shelf storage layout. The mechanism to support and rotate the shelves does require some space, but not as much as a picking aisle. This is an instance when collapsing the space may improve productivity by significantly reducing travel time for those picking.

Carousels are available in an almost unlimited variety of heights, lengths, widths, bin designs and capacities. The machine’s wide range of design configurations had resulted in carousels being used in many different applications in the warehouse and factory. The products stored on carousels can range from tools, hardware and appliances to pharmaceuticals, computer parts, and soft goods.

It has also proven particularly effective in the high-throughput small parts picking. The versatility of the carousels results in applications in space as small as 5 by 15 feet.
Today, carousels are found in filing applications, stockrooms, tool cribs, clean rooms, warehouses and even retail stores.

The different features of Horizontal Carousel

Basically, the supporting structure of top and bottom driven carousels consists largely of welded angles and channels. The basic concept is that a standard drive, idler end sections and standard center sections of different lengths are fit together to form a unit of any length. Extension of the unit is possible at any of the splice joints.

Bins
Standard bins and shelves are generally fabricated of wire. Wire is less expensive than sheet metal, lighter in weight, and dust-free. Where heavier weights are involved, standard wire bins may be strengthened too by using solid sheet-metal supporting bin backs.

The solid backs give bin rigidity, prevent small items from falling through, reduce vertigo effect, and most importantly, support the major portion of the weight of each individual shelf. Therefore, the shelf load is distributed down through the back and through both wire sides.

Shelves are adjustable without use of hardware and each shelf forms a rigid box structure by joining the two sides and back of the bin. Where loads in excess of 100 pounds per shelf are required, high resistance shelves should be used. Shelves are generally pitched 5 to 10 degrees toward the rear to reduce the likelihood of items falling from shelves as bins move.

Bins width and depths vary, as do bin heights allowing great flexibility in carousel system design. Special configurations are quite common.

A major innovation is the twin bin which allows the operator to pick from the left and the right sides of the two different bins, rather than just the front of a single bin. This doubles the volume available for picking at a single bin stop, resulting in improved throughput.

Track
Top-drive units consist of a tubular track supported by poles or stanchions every few feet on which a conveyor chain is mounted. Wire bins are hung from the chain and hang loosely below on a lower track.

Wheels are generally lifetime-sealed bearings mounted at a 45-degree angle that support a hinge pin and connecting chain links. The loads to be carried determine the quantity and size of the wheels used. While larger diameter tracks, wheels and yokes, and hinge pins may be used to carry heavier loads, top-driven units are generally used for lighter loads.

Bottom-drive units use the same tubular track but use a large diameter curved-in steel wheel with axial rollers mounted under a steel-bottom plate. The upper guide track is mounted on stanchions and traps the upper guide wheels. It also tends to deliver better overall performance.

They are more popular because of their ability to carry heavier weights more reliably. Bottom-mounted units also eliminate the potential of product contamination from wheel/track wear, require less overall height, are more adaptable to double tiering, and distribute floor load more evenly.

Drives
Carousel drives are typically located at either end or both ends. Drives on top-driven units may be mounted above the track or below and recessed. Drives are floor-mounted on bottom-drive units and are accessible by the access panel in a bin back. The motors can be either AC or DC.

AC drives are generally used for continuous run and light duty applications. AC motors require a clutch to protect the drive and reduce jerking on start up. On the other hand, DC drives are more expensive and do not require clutches. They should be used wherever a smooth start and stop if required or where stopping accuracy of less than an inch is desired.

Because of the DC motor’s controller allowing in-the-field programming of maximum speed, acceleration and deceleration, the user is provided with a lot more flexibility. Wherever variable speed or a robot picking head is required, a DC drive should be used.

Controls and software
Carousels can be controlled by a wide range of devices but however, the greatest advantages are found with computer control.

In very basic configurations, a single carousel can be controlled using a foot-operated toggle switch. Keypads permit the operator to key in the desired bin number. A microprocessor selects the shortest route. More complicated microprocessor controls reduce carousel rotation by allowing queuing and sorting.

Personal computers control most horizontal carousels. They maybe stand-alone or on a network. Orders are usually downloaded from a host computer.

The order picking software keeps the item location in its memory and has the ability to perform a variety of tasks including batching, sorting by location, sorting by priority, date required, or truck route. The software controls the carousel and the ‘pick-to-light’ process. While the operator picks from one carousel, the other is rotating into position, thus reducing waiting time.

The Pod
This is the basic unit in a carousel system. A typical pod is made of up to 4 to 6 carousels under the command of a single PC and an operator. It includes secondary equipment such as light trees and sort bars; the light displays which guide operator tasks; a barcode scanner; a manifest scanner; a barcode label printer; incoming and outgoing conveyors; a pick table or matrix, and a life table for use with tall carousels.

The pod is the picking center at the nose end of the carousels but can also include other storage equipment such as flow rack and static shelving, in situations where an order may include items with differing demand characteristics, such as count, size of frequency of occurrence.

The pick rate in a carousel pod can run from 200 up to 1200 picks an hour compared to 10 to 30 for static shelving. The pod’s configuration will depend upon pick rate, number of items, other tasks required like bagging or weighing, inventory levels and many other factors.

The picking sequence begins with the arrival of a batch of orders from a supervisor station. When the operator begins the batch, the computer rotates the carousel bins to the location of the first pick from each. The batching takes advantage of the commonality of items on each order to eliminate any duplication of effort.

The batch is sorted to pick the orders to bin sequence, minimizing carousel rotation, and to allow the operator to move form one carousel to the next so that while he or she is picking from the carousel, the last one is repositioning itself for the next pick, thus reducing the possibility of any operator wait time.

Hot picks or emergency demands can be automatically moved through the system without interrupting the flow. The software suspends the routine long enough to do the hot picks then resumes.

Carousels should be used when:

· There is a shortage of space in the facility, especially when aisles can occupy 60% or more of the storage space in the warehouse:

· Manufacturing operations have high ceilings and is facing the problem of limited floor space. As the higher the ceiling, the more density you can get in storage. (For Horizontal Carousel)

· Most importantly, when changes are to be made in the way the products are stored, the function of the physical characteristics of the product to be stored, the frequency of demand for the product, the increment of demand, the rotation requirements of the product, as well as the physical constraints of the building, such as clear height, column spacing or available space should be considered.

That's all Folks!
10:42 AM

0 people bothered to read:

Post a Comment