lec # 7 storage systems

8/10/2019 Lec # 7 Storage Systems

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Department OfMechatronics Engg


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ME-416 Manufacturing Processes,Tooling and Automation

2Lt Col Nasir Rashid (Department of Mechtronics Engg)

Lecture # 7Storage Systems


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ME-416 Manufacturing Processes, Toolingand Automation

Storage System Performance and LocationStrategies

Conventional Storage Methods and Equipment

Automated Storage Systems Engineering Analysis of Storage Systems

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Storage System Function to store materials (e.g., parts, work-in-

process, finished goods) for a period of time andpermit retrieval when required

Used in factories, warehouses, distribution centers,wholesale dealerships, and retail storesImportant supply chain component

Automation available to improve efficiency

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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 storagerelative to total volumetric space in facilityAccessibility - capability to access any item in storage

System throughput - hourly rate of storage/retrievaltransactionsUtilization and availability (reliability)

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Storage Location StrategiesRandomized storage - incoming items are stored in

any available locationUsually means nearest available open location

Dedicated storage - incoming items are assigned tospecific locations in the storage facility

Typical bases for deciding locations:

Items stored in item number sequenceItems stored according to activity levelItems stored according to activity-to-space ratios

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Comparison of Storage StrategiesLess total space is required in a storage system thatuses a randomized storage strategy

Dedicated storage requires space for maximum inventorylevel of each item

Higher throughput rates are achieved in a system thatuses dedicated storage strategy based on activity level

The most active items can be located near the input/outputpoint

Compromise: Class-based dedicated storageItems divided into classes according to activity levelRandom storage strategy used within each class

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Bulk Storage

Bulk storage arrangements: (a) high-density bulk storage provideslow accessibility, (b) bulk storage with loads forming rows andblocks for improved accessibility

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Pallet Rack System

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Drawer Storage

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Automated Storage Systems Mechanized and automated storage equipment to

reduce the human resources required to operate astorage facility

Significant investmentLevel of automation varies

In mechanized systems, an operator participates in eachstorage/retrieval transaction

In highly automated systems, loads are entered orretrieved under computer control

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Objectives of Automated Storage SystemsTo increase storage capacityTo increase storage densityTo recover factory floor space currently used for WIP

To improve security and reduce pilferageTo reduce labor cost and/or increase productivityTo improve safetyTo improve inventory control

To improve stock rotationTo improve customer serviceTo increase throughput

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Analysis of AS/RSSizing the AS/RS Rack StructureAS/RS throughput

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Analysis of AS/RSSizing the AS/RS RackStructure

AssumptionUnit load ( one unit inone compartment)

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Analysis of AS/RSSizing the AS/RS Rack StructureExample

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Analysis of AS/RSAS/RS throughput Assumption

Randomized storage of load

Storage compartments areof equal sizeP/D station is located at thebase and end of aisleConstant horizontal and

vertical speeds of SRmachineSimultaneous vertical andhorizontal travel

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Analysis of AS/RSAS/RS throughputExample

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Analysis of AS/RS (Class based Dedicated Storage)AS/RS throughputExample

The aisles in the AS/RS of the previous example will be organized following aclass-based dedicated storage strategy. There will be two classes, according to

activity level. The more-active stock is stored in the half of the rack systemthat is located closest to the input/output station. and the less-active stock isstored in the other half of the rack system farther away from the input/outputstation. Within each half of the rack system, random storage is used. Themore-active stock accounts for 80% of the transactions. and the less-active

stock accounts for t he remaining 20%. As before, assume that systemutilization = 90%, and the number of single command cycles e the number ofdual command cycles. Determine the throughput of the AS/RS, basing thecomputation of cycle times

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Carousal Storage SystemHorizontal

Operation is similar to overhead conveyor system used indry cleaning establishments

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

VerticalOperates around a vertical conveyor loopLess floor space required, but overhead room must beprovided

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Carousal Storage SystemHorizontal

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Carousal Storage SystemHorizontal (Storage capacity)

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Carousal Storage SystemHorizontal (Throughput Analysis)

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AssumptionsOnly single comd

cycle are performedCarousal operates

with constant speed

The carousal canmove in eitherdirection

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Carousal Storage System

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lec # 7 storage systems

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