A Horizontal Carousel System
Carousels are AS/RS systems being used for main
storage, kitting, progressive assembly, work-in-process (WIP)
in many industries that involve dynamic small-parts storage.
A carousel can be defined as "a series of bins that are linked
together in a continuos chain and mounted on an elongated oval
track" (Weiss, Cramer, 1988). The track is generally
horizontal, but in some situations it is vertical to save floor
space. Another new approach is the " twin-bin
carousel", which provides two faces for pickup in each
carrier.
Horizontal carousels [Figure] consist of closed-loop series
of bins that are hung on a central spine that rotates horizontally
and brings parts to a picking/replenishment station. The entire
carousel rotates each time a new storage location is required.
Twin-bin carousel [Figure] is a variation to the standard
horizontal carousel, except that it allows the picker to pick
from any two sides of a bin.
Vertical carousels [Figure] can be thought of horizontal
carousels in a vertical space. Bins are returned to a front window
for parts picking and replenishment. All bins move when moving
to the next storage location.
Vertical storage module (also named "power column",
"vertical lift AS/RS", "vertical lift module")
is similar to vertical carousel in appearance [Figure], but differs
in its movement. Vertical storage module stores and retrieves
bins without rotating any bins at any time. The module imitates
an AS/RS by only picking the requested bin by traveling vertically
to its location.
Microload/miniload AS/RS consists of an aisle with two
sides, and a storage/retrieval machine that travels along this
aisle and brings parts to picker and performs replenishment.
The S/R machine travels in both horizontal and vertical direction,
and has a load capacity of 250 lb to 1,000 lb.
Besides the above equipment, automated item pickers achieve
very high throughput rates (upto 1500 lines/hr). These devices
are designed to handle small very fast moving, nonfragile items
such as compact disks, pharmaceuticals and books. In one configuration,
a traveling pickhead automatically pulls items from storage onto
a conveyor belt. In another case, products are arranged over
the conveyor belt. Each magazine contains a powered mechanism
that automatically dispenses items onto a conveyor belt (Modern Materials Handling, MID March 1993).
Dynamic part-to-picker storage devices gain advantage in situations where higher throughput requirements, more flexibility, and more accuracy are desired. They are more costly compared to static storage devices, but may decrease "total cost" in the facility when implemented. As stated earlier, most warehouses/storage environments use a combination of static/dynamic devices to achieve the best overall performance. The basic reason for this is that different items that are handled in the same facility can have significantly differing characteristics.
Special equipment such as scissor lifts,
mezzanines, and insert/extract
mechanisms can significantly improve the versatility of order
picking from part-to-man systems when used as appropriate interfaces.
Video on Conveyor Sorting Systems, 1, courtesy of Rapistan Demag Co.
Video on Conveyor Sorting Systems, 2, courtesy of Rapistan Demag Co.
Video from J.C. Penney Distribution Center in
Atlanta, GA courtesy of Rapistan Demag Co.
