Storage Systems

Sections:1. Storage System Performance and Location Strategies2. Conventional Storage Methods and Equipment3. Automated Storage Systems4. Engineering Analysis of Automated Storage Systems

Storage Systems

Function – to store materials (e.g., parts, work-in-process, finished goods) for a period of time and permit retrieval when required

Used in factories, warehouses, distribution centers, wholesale dealerships, and retail stores

Important supply chain component Automation available to improve efficiency

Storage System Performance

Performance measures for storage systems: Storage capacity - two measures:

Total volumetric space Total number of storage compartments (e.g., unit loads)

Storage density - volumetric space available for storage relative to total volumetric space in facility

Accessibility - capability to access any item in storage System throughput - hourly rate of storage/retrieval

transactions Utilization and availability (reliability)

Storage Location Strategies

Two strategies: 1. Randomized, and 2. Dedicated

Randomized storage – . Incoming items are stored in any available location. Usually means nearest available open location

Dedicated storage – Incoming items are assigned to specific locations in the storage facility Typical bases for deciding locations:

Items stored in item number sequence Items stored according to activity level Items stored according to activity-to-space ratios

Conventional Storage Methods

Bulk storage - storage in an open floor area Problem: achieving proper balance between storage

density and accessibility Rack systems - structure with racks for pallet loads

Permits vertical stacking of materials Shelving and bins - horizontal platforms in structural

frame Steel shelving comes in standard sizes Finding items can be a problem

Drawer storage - entire contents of each drawer can be viewed

Bulk Storage

Bulk storage arrangements: (a) high-density bulk storage provides low accessibility, (b) bulk storage with loads forming rows and blocks for improved accessibility(c) Low cost per sq meter

Pallet Rack System

Pallet loads placed on racks in multi-rack structure

(a) Low cost

(b) Good stroge density

(c) Good accessibility

Drawer Storage

Contents easily visible Good accessibility Relatively high cost

Small items (tools, repair parts, etc.)

Automated Storage Systems

Mechanized and automated storage equipment to reduce the human resources required to operate a storage facility

Significant investment Level of automation varies

In mechanized systems, an operator participates in each storage/retrieval transaction

In highly automated systems, loads are entered or retrieved under computer control

Objectives and Reasons for Automating Storage Operations

To increase storage capacity To increase storage density To recover factory floor space currently used for WIP To reduce labor cost and/or increase productivity To improve safety To improve inventory control To improve stock rotation To improve customer service To increase throughput

Types of Automated Storage System

1. Automated Storage/Retrieval System (AS/RS) Rack system with mechanized or automated crane to

store/retrieve loads2. Carousel Storage System

Oval conveyor system with bins to contain individual items

AS/RS

Unit load on pallet AS/RS with one aisle

AS/RS Types

Unit load AS/RS - large automated system for pallet loads Deep-lane AS/RS - uses flow-through racks and fewer

access aisles Miniload AS/RS - handles small loads contained in bins or

drawers to perform order picking Man-on-board AS/RS - human operator rides on the

carriage to pick individual items from storage Automated item retrieval system - picks individual items Vertical lift storage modules (VLSM) - uses a vertical

aisle rather than a horizontal aisle as in other AS/RS types

• The AS/RS Unit Load technology designed to handle unitized loads into and out of very high density storage.

• While sometimes used to replenish picking locations with palletized commodities.

• The most common application of this equipment is for the buffering of supply chain deliveries, storing and controlling the inventory until it has been released from QC, or is requested out for use in downstream processes.

• This would include the buffering of palletized finished goods waiting for distribution to the end user.

Unit Load AS/RS

• The unique compact design of the Mini Load AS/RS allows you to store more material in less space.

• This AS/RS is designed with strong, lightweight alloys making the mini load less expensive to install, operate, and maintain.

• The most common usage of this class of AS/RS is for small parts storage and management for picking and order fulfilment.

• Often paired with a hybrid combination of Carousels, flow lanes and static racks or shelves, the Miniload provides the best solution for those small parts like nuts, bolts, hand tools that represent the mid-range of activity.

Mini load AS/RS

• Used for in-aisle picking; operator picks from shelves, bins, or drawers within the storage structure.

• Manual or automatic control S/R machine is similar to an order picker or turret truck and can sometimes operate as an industrial truck when outside an aisle, except the S/R is guided along a rail when operating in an aisle.

Man-On-Board AS/RS

• Similar to unit load AS/RS, except loads can be stored to greater depths in the storage rack.

• A rack-entry vehicle is used to carry loads into the racks from the S/R machine, and is controlled by the S/R machine.

• Another S/R machine functions as a retrieval vehicle to extract the parts from the other end of the storage lane.

Deep-Lane AS/RS

• These systems are also designed for retrieval of individual items or small unit loads such as cases of product in a distribution warehouse.

• However, in this system, the items are stored in single-file lanes rather then in bins or drawers.

• When an item (or case) is to be retrieved, it is released from its lane onto a conveyor for delivery to the pickup station.

Automated item retrieval system

1.Storage structure / Bins2.S/R Machine3.Storage module (Pallet Loads)4.Pick and deposit station5.Control system

Components of an AS/RS

AS/RS Applications

1. Unit load storage and retrieval Warehousing and distribution operations AS/RS types: unit load, deep lane (food industry)

2. Order picking AS/RS types: miniload, man-on-board, item retrieval

3. Work-in-process storage Helps to manage WIP in factory operations Buffer storage between operations with different production rates Supports JIT manufacturing strategy Kitting of parts for assembly

Carousel Storage Systems

Horizontal Operation is similar to overhead conveyor system used

in dry cleaning establishments Items are stored in bins suspended from the conveyor Lengths range between 3 m and 30 m Horizontal is most common type

Vertical Operates around a vertical conveyor loop Less floor space required, but overhead room must be

provided

Horizontal Carousel Storage System

Manually operated horizontal carousel storage system

Vertical Carousel Storage System

Features of a Vertical Carousel System1.Carriers / bins — attached to the rotating mechanism2.Multifunction Carrier — for variable applications3.Drive System — housed internally4."Soft Start" Control — uses three phase motors5.Work Counter — made of high-grade stainless steel6.Rack for item retrieval and storage by operator7.Light Barriers8.Microprocessor Control Unit9.Wiring Cabinet — located for easy access10.Multifunction Positioning System11.Lockable Sliding Doors — provide protection of stored

items12.Protective Cover13.Maintenance Access—at the front.

Carousel Applications

1. Storage and retrieval operations Order picking Kitting of parts for assembly

2. Transport and accumulation Progressive assembly with assembly stations located

around carousel3. Work-in-process

WIP applications in electronics industry are common

Engineering Analysis of Automated Storage Systems

1. Automated Storage/Retrieval Systems Sizing the AS/RS AS/RS throughput analysis

2. Carousel storage systems Storage capacity Throughput analysis