ME4262 - AIMAuto Storage & Retrieval System

A/P Lee Kim Seng

Auto Storage & Retrieval System(Summary)

A/P Lee Kim Seng

• Objectives

• Storage system performance

• Performance Criteria- storage capacity- system throughput- utilization- uptime reliability

• Common types of Auto-storage systems- AS/RS- Mechanized carousel systems

A/P Lee Kim Seng

• Categories of AS/RS- Unit load AS/RS- Miniload AS/RS- Man-on-board AS/RS- Automated item retrieval system- Deep lane AS/RS

• Basic components of an AS/RS- storage structure- S/R machines- storage module (pallet or Unit load)- pickup & deposit stations (P/D)

Auto Storage & Retrieval System(Summary cont..)

A/P Lee Kim Seng

• Other features in AS/RS- Aisle transfer car- Full/Empty bin detectors- Sizing station- Load identification stations

• AS/RS controls

• Application of AS/RS

• Quantitative analysis of Carousel Storage System

Auto Storage & Retrieval System(Summary cont..)

A/P Lee Kim Seng

• Carousel Storage System

• Control of Carousel Storage SystemManual - Foot pedal control

- Hand control- Keyboard control

Computer control

• Quantitative analysis of Carousel storage system

Auto Storage & Retrieval System(Summary cont..)

A/P Lee Kim Seng

Interfacing Materials Handling & Storage with Manufacturing

- Information interface- Mechanical Interface

Auto Storage & Retrieval System(Summary cont..)

A/P Lee Kim Seng

A/P Lee Kim Seng

Table 15.1 Types of Materials Typically Stored in a Factory

Records on product, maintenance records, etc.Plant records9

Supplies and other items used in support of plant and company office staff

Office supplies8

Spare parts used to repair machines and equipment in the factory

Spare parts7

Cutting tools and supplies used in the manufacturing and assembly operations

Tooling6

Parts that are out of specification, either to be reworked or scrapped; chips and swarf, other materials that must be discarded by the factory

Rework and scrap5Completed product ready to be shipped to customerFinished product4

Partially completed parts between processing and assembly operations

Work-in-process3

Parts from vendors to be processed or assembled by factoryPurchased parts2Raw stock to be processed or assembled by factoryRaw materials1DescriptionType

A/P Lee Kim Seng

Different companies have different reasons for installing an automated storage system

Objectives:1. Increase storage capacity2. Increase floor space utilization3. Recover space for manufacturing facilities4. Improve security and reduce pilferage5. Reduce labour cost in storage operations6. Increase labour productivity in storage operations7. Improve safety in storage function8. Improve control over inventories9. Increase stock rotation10. Improve customer service

A/P Lee Kim Seng

A/P Lee Kim Seng

It is important in designing the storage system that a malfunction of one component or a section does not cause the entire system to be down A/P Lee Kim Seng

The total maximum number of individual parts that are expected to be stored

• Physical capacity of the storage system should be greater than the actual maximum number of parts that will be stored

• Provide available empty spaces for materials being entered into the system

• Allow for variations in maximum storage requirements

A/P Lee Kim Seng

Defined as the number of parts/loads per hour that the storage system can

a. Receive and place into storage and

b. Retrieve and deliver to the output station

The storage system must be designed for the maximum required throughput that will occur during the day

A/P Lee Kim Seng

A/P Lee Kim Seng

Storage transaction cycle time consist of:− Time to pick up the part at the input station− Time to determine the storage location− Travel time to the storage location− Unloading time at the storage location− Return travel time

Retrieval transaction cycle time consist of:− Time to determine the storage location of the part− Travel time to the storage location− Time to pick the part/item from storage− Return travel time− Unloading time at the output station

A/P Lee Kim Seng

The throughput capacity is also limited by the capability of the materials handling system that is interfaced with the storage system

If the materials handling system is incapable of delivering parts to or removing parts from the storage system at a rate that is compatible with the transaction cycle time, the throughput of the storage system will be adversely affected

A/P Lee Kim Seng

Utilization of the storage system is defined as the percentage of time that the system is in use compared to the time it is available

• It is desirable to design the storage system for relatively high utilization, perhaps in the range of 80% to 90%

A/P Lee Kim Seng

It is defined as the percentage of time that the system is capable of operating compared to the normal scheduled time of system operation (Sometimes also known as Availability)

• Malfunctions of the equipment, both mechanical and electrical (e.g computer) cause downtime that prevent the system from operating

A/P Lee Kim Seng

A/P Lee Kim Seng

An automated storage / retrieval system (AS/RS) is defined by the Materials Handling Institute as follow:

A combination of equipment and controls which handles, stores, and retrieves materials with precision, accuracy, and speed under a defined degree of automation

A/P Lee Kim Seng

• Consists of a series of storage aisles that are serviced by one or more storage/retrieval (S/R) machines, usually one S/R machine per aisle

• Aisles have storage racks for holding materials to be stored

• S/R machines used to deliver/retrieve materials to/from the racks

• AS/RS may have one or more input/output stations [pickup-and-deposit (P&D) stations] where materials are delivered/picked up from the system

A/P Lee Kim Seng

1. Unit load AS/RS – A large automated system designed to handle unit loads stored on pallets or other standard containers.

This system is computer-controlled and the S/R machines are automated and designed to handle the unit load containers

A/P Lee Kim Seng

A/P Lee Kim Seng

A/P Lee Kim Seng

A/P Lee Kim Seng

2. Miniload AS/RS – Used to handle individual parts or supplies contained in bins or drawers within the storage system.

S/R machine designed to retrieve the bin and deliver it to P&D station (manually operated) at the end of the aisle so that the individual items can be withdrawn from the bin.

Bin is returned to its location in the systemA/P Lee Kim Seng

A/P Lee Kim Seng

A/P Lee Kim Seng

A/P Lee Kim Seng

3. Man-on-board AS/RS – The man-on-board system permits individual items to be picked directly at their storage locations.

The transaction time is thus reduced.

A/P Lee Kim Seng

A/P Lee Kim Seng

A/P Lee Kim Seng

4. Automated item retrieval system – Items are stored in single-file lanes rather than in bins. When an item is to be retrieved, it is released from its lane onto a conveyor for delivery to the pickup station.

Supply of items in each lane is replenished from the rear of the retrieval system so that there is flow-through of the items, thus permitting first-in/first-out inventory control.

A/P Lee Kim Seng

A/P Lee Kim Seng

5. Deep-lane AS/RS – This system is suitable when large quantities are to be stored but the number of separate types of materials is relatively small. The system stores up to 10 or so loads in a single rack, one load behind the next.

Each rack is designed for ‘flow-through’, with input on one side and output on the other side.

A/P Lee Kim Seng

A/P Lee Kim Seng

1.Storage structure

2.Storage/retrieval (S/R) machine(3 drive systems are required: Horizontal, vertical and shuttle)

3.Storage modules (e.g. pallets or unit loads)

4.Pickup and deposit stationsA/P Lee Kim Seng

A/P Lee Kim Seng

1. Aisle transfer carsAisle transfer cars are used to move S/R machines back and forth between aisles to perform the storage and retrieval functions. (in the case of low activity per aisle)

2. Full/empty bin detectors

3. Sizing stationsUse to ensure that oversized loads do not enter into the AS/RS.

4. Load identification stationsA/P Lee Kim Seng

A/P Lee Kim Seng

• Each compartment is identified by a location number, based on alphanumeric codes, which indicates aisle, horizontal position, and vertical position in the structure.

• Record of these locations is called the item location file. Each time a storage transaction is completed, a record of the transaction must be entered into the item location file.

A/P Lee Kim Seng

Computer controls and programmable controllers are used to determine the required location and guide the S/R machine to its destination

A/P Lee Kim Seng

Computer control permits the physical operation of the AS/RS to be integrated with the supporting information and record-keeping system

A/P Lee Kim Seng

Storage transactions can be entered in real time, inventory records can be accurately maintained, system performance can be monitored, and communications can be facilitated with other factory computer systems

A/P Lee Kim Seng

A/P Lee Kim Seng

(miniload, man-on-board)

A/P Lee Kim Seng

Focus on capacity and operating performance of the AS/RS

A/P Lee Kim Seng

Let nv = the number of vertical load compartment to be arranged

Let nh = the number of horizontal load compartment to be arranged

Capacity per aisle = 2 nv nh

Assumed that parts/loads are stored on both sides of the aisle

Let x = horizontal dimension of a unit load

Let y = vertical dimension of a unit load

Thus the height and length of the AS/RS aisle will be: (Tompkin)

Hs = nv ( y + 0.25 m )

Ls = nh ( x + 0.25 m )

Tolerance

Tolerance

A/P Lee Kim Seng

System Throughput was defined as the number of storage transactions per hour that the AS/RS is capable of accomplishing

A Single-Command Cycle involves either entering a load into storage, or retrieving a load from storage, but not both in one cycle

A Dual-Command Cycle involves both entering a load into storage and retrieving a load from storage in the same cycle

A/P Lee Kim Seng

Assumptions made (Computation of transaction cycle time) :1. Randomized storage of loads in the AS/RS

2. The storage compartments are of equal size

3. The P&D station is located at the base and at the end of the aisle

4. Constant horizontal and vertical speed of the S/R machine

5. Simultaneous horizontal and vertical travelA/P Lee Kim Seng

Let Vh and Vv be the horizontal and vertical speed of the S/R machine

Lsth =

Vh

Hstv =

Vv

Then, the following two parameters can be defined:

T = max ( th, tv )

th tvQ = min ( , )

T T

A/P Lee Kim Seng

The average single-command transaction time is given by:

Q2

Tsc = T ( + 1 ) + 2 Tpd3

Tpd = shuttle time to perform a pickup or deposit

The average dual-command transaction time is given by:

4 Q3

Tdc = T ( + 0.5Q2 - ) + 4 Tpd3 30

A/P Lee Kim Seng

Consider the operation of a unit load AS/RS that uses an S/R machine for each aisle of the system. The length of the storage aisle is 300 ft and its height is 50 ft. Horizontal and vertical travel speeds of the S/R machine are 400 ft/min and 75 ft/min, respectively. The S/R machine requires 30 sto accomplish a P&D operation.Determine the single-command and dual-command cycle times for the storage system.

A/P Lee Kim Seng

The values of th and tv are computed as

Lsth =

Vh

Hstv =

Vv

300 ftth = = 0.75 min

400 ft/min

50 fttv = = 0.667 min

75 ft/min

T = max ( th, tv )

th tvQ = min ( , )

T T

T = max ( 0.75, 0.667 ) = 0.75 min

0.667Q = min ( 1.0 , ) = 0.8889

0.75A/P Lee Kim Seng

The single-command transaction time is

Q2

Tsc = T ( + 1 ) + 2 Tpd3

0.88892

Tsc = 0.75 ( + 1 ) + 2 (0.50) 3

= 1.9475 min

The dual-command transaction time is

4 Q3

Tdc = T ( + 0.5Q2 - ) + 4 Tpd3 30

4 0.88893

Tdc = 0.75 ( + 0.5(0.8889)2 - ) + 4 (0.50)3 30

= 3.2786 min

A/P Lee Kim Seng

A/P Lee Kim Seng

(ranging from 3 to 30 m in length).

A/P Lee Kim Seng

It is mechanized rather than automated.

The load/unload station is manned by a human worker who activates the powered carousel to deliver a desired bin to the station.

A/P Lee Kim Seng

Video clip “horizontal_carousel”

A/P Lee Kim Seng

A/P Lee Kim Seng

Video clip “verticlecine”

A/P Lee Kim Seng

A/P Lee Kim Seng

A/P Lee Kim Seng

A/P Lee Kim Seng

• Permits greater variety of control features• Operator can enter the desired bin position and the carousel is programmed to determine the shortest route to deliver the bin to the pick station.

• Contains controls for bi-directional jogging of the carousel, and emergency stop controls

A/P Lee Kim Seng

• Are implemented using various computer configurations, from microprocessor-based controllers for individual carousels to centralized delicated mini-computers that control multiple carousels

• Features include the capability to maintain data on:

− Bin locations− Items in each bin− Inventory control records

A/P Lee Kim Seng

A/P Lee Kim Seng

The circumference of the carousel track is given by:

C = 2 ( Ls – Ws ) + ππππWs

Let nc = number of carriers

Let sc = spacing between carriers

then nc sc = C

If nb = Number of separate bins hung from a carrier

Then the total number of bins on the carousel = nb nc

A/P Lee Kim Seng

Assumptions made:

1. A transaction cycle consists of either a retrieval or a storage, but not both (Single command transaction)

2. The speed of the carousel is constant (Vc)

3. Random storage is used in the carousel

A/P Lee Kim Seng

For a single direction carousel, average travel distance is given by:

Lr = 0.5C

Time to complete a retrieval transaction, Tr is

0.5CTr = + Th

Vc

For dual directions carousel,

Lr = 0.25C

0.25CTr = + Th

Vc A/P Lee Kim Seng

The oval of a top-driven carousel track has a length = 50 ft and width = 4 ft. The speed of the carousel = 75 ft/min. There are 50 carriers around the carousel, and each carrier has 5 bins suspended from it.

For a single-direction carousel and a bi-directionalcarousel, compare how long will it take to retrieve 20 parts from the carrier if each part is in a different storage bin and random storage is used in the carousel.

Also, determine the spacing between carriers on the carousel. The handling time associated with a retrieval = 20 s.

A/P Lee Kim Seng

The circumference of the carousel track is

C = 2 ( Ls – Ws ) + ππππWsC = 2 ( 50 – 4 ) + 4ππππ

= 104.57 ft

For a single direction carousel, the retrieval of 20 parts would require

0.5CTr = + Th

Vc

104.5720Tr = 20 ( 0.5 x + 0.333 )

75= 20.61 min

A/P Lee Kim Seng

For a bi-directional carousel, the retrieval time for 20 parts would be

0.25CTr = + Th

Vc

104.5720Tr = 20 ( 0.25 x + 0.333 )

75= 13.63 min

The spacing between carriers along the carousel would be

Csc =

nc

104.57sc =

50= 2.091 ft

A/P Lee Kim Seng

A/P Lee Kim Seng

Interfacing Material Handling & Storage with Manufacturing

A/P Lee Kim Seng

A/P Lee Kim Seng

This concerns with the flow of information that must accompany the movement and storage of materials in the factory

(materials identification and tracking, inventory control, production scheduling, and data communications required to coordinate and control the various system in the plant)

A/P Lee Kim Seng

This deals with the problems of transferring parts and loads between storage systems, material handling systems, and production systems

The design of the mechanical interface depends on:

- The type of handling equipment used- The system that is to be interfaced with the

handling system- Whether manual or automated loading/unloading

A/P Lee Kim Seng

Problems in mechanical interfacing include:1. Positional accuracy of the handling

system at the transfer station

2. Methods of transferring parts or loads to and from the handling system

A/P Lee Kim Seng

A/P Lee Kim Seng