Storage Systems-3e-S 10-01, 01/06, 06/04/07
Materials stored in manufacturing include a variety of types. Name six of the ten categories listed in Table
: The material types listed in Table 11.1 are (1) raw materials, (2) purchase parts, (3) work-in-process,
(4) finished product, (5) rework and scrap, (6) refuse, (7) tooling, (8) spare parts, (9) office supplies, and (10)
Name and briefly describe four of the six measures used to assess the performance of a storage system?
: The six performance measures discussed in the text are the following: (1) storage capacity, which is
defined and measured either as the total volumetric space available or as the total number of storage
compartments in the system available for items or loads; (2) storage density, defined as the volumetric
space available for actual storage relative to the total volumetric space in the storage facility; (3)
accessibility, which refers to the capability to access any desired item or load stored in the system; (4)
system throughput, defined as the hourly rate at which the storage system receives and puts loads into
storage and/or retrieves and delivers loads to the output station; (5) utilization, which is defined as the
proportion of time that the system is actually being used for performing storage and retrieval operations
compared with the time it is available, and (6) availability, defined as the proportion of time that the
system is capable of operating (not broken down) compared with the normally scheduled shift hours.
Briefly describe the two basic storage location strategies.
: The two basic strategies are (1) randomized storage and (2) dedicated storage. In randomized
storage, items are stored in any available location in the storage system. In the usual implementation of
randomized storage, incoming items are placed into storage in the nearest available open location. When
an order is received for a given SKU, the stock is retrieved from storage according to a first-in-first-out
policy so that the items held in storage the longest are used to make up the order. In dedicated storage,
SKUs are assigned to specific locations in the storage facility. This means that enough locations are
reserved for all SKUs stored in the system, and so the number of storage locations for each SKU must be
sufficient to accommodate its maximum inventory level.
What is a class-based dedicated storage strategy?
: A class-based dedicated storage allocation is a compromise between a randomized storage
strategy and a dedicated storage strategy. The storage system is divided into several classes according to
activity level, and a randomized storage strategy is used within each class. The classes containing more-
active SKUs are located closer to the input/output point of the storage system for increased throughput, and
the randomized locations within the classes reduce the total number of storage compartments required.