Page 240 - DMGT523_LOGISTICS_AND_SUPPLY_CHAIN_MANAGEMENT

Unit 10: Packaging and Material Handling

advantage of a towline is continuous movement. However, such handling devices do not Notes
have the flexibility of forklift trucks. The most common application of towlines is for
order selection within the warehouse. Order selectors place merchandise on a four-wheel
trailer, which is then towed to the shipping dock. A number of automated decoupling
devices have been perfected that route trailers from the main line to selected shipping
docks.
A point of debate involves the relative merits of in-floor and overhead towline installation.
In-floor installation is costly to modify and difficult to maintain from a housekeeping
viewpoint. Overhead installation is more flexible, but unless the warehouse floor is
absolutely level, the line may jerk the front wheels of the trailers off the ground and risk
product damage.

4. Tow Tractor with Trailers: A tow tractor with trailer consists of a driver guided power
unit towing a number of individual four-wheel “trailers” that hold several palletized
loads. The typical size of the trailers is 4 by 8 feet. The tow tractor with trailer, like the
towline, is typically used to support order selection. The main advantage of tow tractor
with trailers is flexibility. It is not as economical as the towline because it requires greater
labour participation and is often idle. Considerable advancements have been made in
automated-guided vehicle systems (AGVS). These are discussed under semi automated
material handling.
5. Conveyors: Conveyors are used widely in shipping and receiving operations and form
the basic handling device for a number of order selection systems.
Conveyors are classified according to:
(a) Power

(b) Gravity
(c) Roller or belt movement
In power systems, the conveyor uses a drive chain from either above or below. Considerable
conveyor flexibility is sacrificed in such power configuration installations.

Did u know? Gravity and roller or belt systems permit the basic installation to be
modified with minimum difficulty.
Portable gravity-style roller conveyors are often used at the warehouse for loading and
unloading and, in some cases, are transported on over-the-road trailers to assist in unloading
at the destination.
6. Carousels: A carousel operates on a different concept than most other mechanized handling
equipment. It delivers the desired item to the order selector by using a series of bins
mounted on an oval track. The entire carousel rotates and brings the desired bin to the
operator. A wide variety of carousels are available. The typical application involves
selection of individual packages in pack and repack as well as service parts operations.
The rationale behind carousel systems is to shrink order selection labour requirements by
reducing walking length/paths and time. Carousels, particularly modern stackable or
multitiered systems, also significantly reduce storage floor requirements.
7. Pick-to-Light Systems: Technology has also been applied to carousel systems in an
application known as “pick to light.” In these systems, order selectors pick designated
items and put them directly into cartons from carousel bins or conveyors. A series of
lights or a “light tree” in front of each pick location indicates the number of items to pick

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