CELLULAR MANUFACTURING & FLEXIBLE MANUFACTURING SYSTEM - UNIT 5 - CAD & M

ME8691
COMPUTER AIDED DESIGN & MANUFACTURING
UNIT 5 – CELLULAR MANUFACTURING &
FLEXIBLE MANUFACURING SYSTEM (FMS)
S.BALAMURUGAN
ASSISTANT PROFESSOR
MECHANICAL ENGINEERING
AAA COLLEGE OF ENGINEEERING & TECHNOLOGY

MANUFACTURING TREND
ME 8691 COMPUTER AIDED DESIGN & MANUFACTURING S.BALAMURUGAN, AP/MECHANICAL, AAACET

TYPES OF AUTOMATION

LEVEL OF AUTOMATION

TYPES OF AUTOMATION
Features
Types of Automation
Fixed Programmable Flexible
Initial
Investments
High in custom
engineered
equipment
High in general purpose
equipment
High in custom
engineered equipment
Production
Rates
High Low to medium Medium
Flexibility
Inflexible Suitable to
accommodate changes
in product configurations
Flexible to
accommodate product
design variations
Production
System
Mass
Manufacturing
Batch Manufacturing Continuous production
of variable mixtures
Tooling Fixed Tooling Tools & Fixtures as per
production batch
Tool changes are quick
& efficient
Setup Time No setup time as
the type of
production does
not vary
Setup time varies from
batch to batch
Minimal setup time

GROUP TECHNOLOGY
• Major form of production activity – Batch Manufacturing
• To make this mode of manufacturing as productive as possible, Integrate design & manufacturing
functions at the initial step leading to complete integration.
• GT is a theory of management based on the principle that similar things should be done similarly.
• GT is a manufacturing philosophy in which similar parts are identified & grouped together to take
advantage of their similarities in Design & Production.
WHERE TO IMPLEMENT GT?
• Plants using traditional batch production & process type layout.
• If the parts can be grouped into part families.
PROCESS
LAYOUT

IMPLEMENTING GROUP TECHNOLOGY
There are two major tasks that a company must undertake when it implements Group
Technology.
1. IDENTIFYING THE PART FAMILIES.
• If the plant makes 10,000 different parts, reviewing all of the part drawings and
grouping the parts into families is a substantial task that consumes a significant
amount of time.
2. REARRANGING PRODUCTION MACHINES INTO CELLS
• It is time consuming and costly to plan and accomplish this rearrangement, and the
machines are not producing during the changeover.

Throughput Time – It is the time that it takes for a product to be manufactured.
(Processing Time + Inspection Time+ Move Time + Queue Time)
Cellular Manufacturing – It is a manufacturing process that produces families of
parts within a single line or cell of machines
Manufacturing Cell – A cell is a cluster of machines grouped together to produce a
part family
Part Family – A collection of parts that posses similarities in geometry, shape, size or
in processing steps used in their manufacture

GROUP TECHNOLOGY (GT)
BENEFITS OF GROUP TECHNOLOGY
• GT promotes standardization of tooling, fixturing, and setups.
• Material handling is reduced because parts are moved within a
machine cell rather than within the entire factory.
• Process planning and production scheduling are simplified
• Setup times are reduced, resulting in lower manufacturing lead times.
• GT can be implemented by manual or automated techniques.
• When automated, the term flexible manufacturing system(FMS) is
often applied.
• Grouping the production equipment into machine cells, where each
cell specializes in the production of a part family, is called cellular
manufacturing.

• DESIGN ATTRIBUTES – Related to shape, Geometry & the
size of the parts.
• Shape, Dimensions, Tolerances, Finish, Material.
• MANUFACTURING ATTRIBUTES – Related to the
sequence of processing steps required to manufacture
the part.
• Production Process, Operational time, Tools
required, Fixture required, Batch size
• GT begins with formation of groups or part families.
• The parts grouped within a family are different, but close
enough to be identified as members of the family.
• The major difficulty in applying GT is setting up the part
families.
• Visual Inspection
• Composite Part Concept
• Production Flow Analysis
• Part Classification & Coding System
GROUP TECHNOLOGY
DESIGN ATTRIBUTES
MANUFACTURING ATTRIBUTES

PART FAMILY CONCEPT
• A part family is a collection of parts that are similar either because of
geometric shape and size or because similar processing steps are required
in their manufacture.
• The parts within a family are different, but their similarities are close enough
to merit their inclusion as members of the part family.
Rotational part family
requiring similar turning
operations
Similar prismatic parts
requiring similar milling
operations
Dissimilar parts requiring
similar machining operations
(hole drilling, surface milling
Identical designed parts requiring
completely different manufacturing
processes
MODEL 1
STEEL
MODEL 2
PLASTIC

WAYS TO IDENTIFY PART FAMILIES
VISUAL INSPECTION
• It is the least sophisticated and least expensive method.
• It involves the classification of parts into families by looking at either
the physical parts or their photographs and arranging them into groups
having similar features.
PARTS CLASSIFICATION AND CODING
• Identifying similarities and differences among parts and relating them
by means of a coding scheme.
• Design attributes
• Manufacturing attributes
PRODUCTION FLOW ANALYSIS (PFA)
• It is a method for identifying part families & associated machine
groupings that uses the information contained on process plans (route
sheets) rather than on part drawings.
• Parts with identical or similar process plans are classified into part
families.
• These families can then be used to form logical machine cells in a
group technology layout.

COMPOSITE PART CONCEPT
• It is based on the features of all the components
forming a group.
• The various operations are required to complete
group of parts.
• Composite Part requires all the operations of the
group.
• The tool setting is done for this composite part.
• To produce any actual part of the group, operations
are added or deleted corresponding to the
requirements of the part.
• This concept is then extended by setting up a
machine cell.
WAYS TO IDENTIFY PART FAMILIES

Design & Manufacturing area gets benefited by this method.
Most classification & coding system are one of the following
• On the basis of Design Attributes
• On the basis of Manufacturing Attributes
• On the basis of both, Design & Manufacturing Attributes
• A part coding system consists of a sequence of symbols that identify the
part’s design & manufacturing attributes.
• The symbols are usually alphanumeric, although most systems use only
numbers.
THE THREE BASIC CODING STRUCTURES ARE:
1. CHAIN-TYPE STRUCTURE
• Also known as Polycode, in which
the interpretation of each symbol in
the sequence is always the same.
• It does not depend on the value of
the preceding symbols.

2. Hierarchical structure, also known as a Monocode, in which the
interpretation of each successive symbol depends on the value of the
preceding symbols.
3. Hybrid structure - Mixed Mode – Optiz Part Classification System,
a combination of hierarchical and chain-type structures.
If the code is 2 digit, Ex – 15 or 25
First Digit
1 – Cylindrical, 2 – Rectangular
Second Digit
5 – L/D Ratio of cylindrical object
5 – Aspect Ratio of rectangular object

OPTIZ CLASSIFICATION AND CODING SYSTEM
It is intended for machined parts and uses the following digits sequence
• Form Code 1 2 3 4 5 - Design attributes
• Supplementary Code 6 7 8 9 - Manufacturing attributes
• Secondary Code A B C D - Production operation type & sequence

OPTIZ CLASSIFICATION AND CODING SYSTEM

BASIC STRUCTURE OF OPTIZ PARTS CLASSIFICATION & CODING SYSTEM
Form Code 1 2 1 3 2
1. Part Class – Rotational – L / D = 2
2. External Shape – Stepped to one end or
Smooth, Thread
3. Internal Shape – Smooth or Stepped to one
end, No shape elements
4. Surface Machining – External Slot
5. Additional Hole – Axial on Pitch Circle
Diameter

BASIC STRUCTURE OF OPTIZ PARTS CLASSIFICATION & CODING SYSTEM
Form Code 6 5 4 4 3 6 0 7 0
1. Part Class (6) – Non-Rotational – Flat - A/B ≤ 3, A/C ≥ 3
2. External Shape (5) – Flat small deviations from casting
3. Internal Shape (4) – Main Bores are parallel
4. Surface Machining (4) – Plane Stepped Surface
5. Additional Hole (3) – Drilling pattern for holes drilled in one direction
6. Dimensions (6) – Edge Length A > 400 ≤ 600
7. Material (0) – Cast Iron
8. Internal Form (7) – Cast
9. Accuracy (0) – Surface Finish – None.

PRODUCTION FLOW ANALYSIS
• It is a method for identifying part families & associated machine groupings
that uses the information contained on process plans (route sheets) rather
than on part drawings.
• Parts with identical or similar process plans are classified into part families.
• It can then be used to form logical machine cells in a group technology
layout.
The minimum data needed in the analysis are the part
number & operation sequence, which is obtained from
process plans.
A sortation procedure is used to group parts with
identical process plans
The processes used for each group are displayed in
this chart
From the pattern of data in the PFA chart, related
groupings are identified & rearranged into a new pattern
that brings together groups with similar machine
sequences.

RANK ORDER CLUSTERING
• It is used for performing cluster analysis to form a machine cell.
PROBLEM - Apply the Rank order clustering technique to the part-machine
incidence matrix in the following table to identify logical part families and
machine groups. Parts are identified by letters & machines are identified
numerically.
1. DEVELOP PART INCIDENCE MATRIX ACCORDING TO THE ROUTE SHEETS
• In this matrix “1” indicates the parts to be machined corresponding
machines. “0”s not indicated & left as a blank for better clarity.
MACHINES
PARTS
A B C D E F G H I
1 1 1 1
2 1 1
3 1 1 1
4 1 1
5 1 1
6 1 1
7 1 1 1

2. FIND DECIMAL EQUIVALENT & RANKING THE MATRIX IN ROW WISE
• Assign Binary number for corresponding column – Right to Left
• Find Decimal Value – Row 1 = ( 1 × 28 ) + ( 1 × 25 ) + ( 1 × 21 )
= 256 + 32 + 2 = 290
MACHINES
PARTS
28 27 26 25 24 23 22 21 20 DECIMAL
EQUIVALENT
RANK
A B C D E F G H I
1 1 1 1 290 1
2 1 1 17 7
3 1 1 1 81 5
4 1 1 136 4
5 1 1 258 2
6 1 1 65 6
7 1 1 1 140 3

3. REORDER THE ROWS IN THE PART MACHINE INCIDENCE MATRIX
• Reorder the rows in the part machine incidence matrix by listing them in
decreasing order starting from top.
MACHINES
PARTS
28 27 26 25 24 23 22 21 20 DECIMAL
EQUIVALENT
RANK
A B C D E F G H I
1 1 1 1 290 1
5 1 1 258 2
7 1 1 1 140 3
4 1 1 136 4
3 1 1 1 81 5
6 1 1 65 6
2 1 1 17 7

4. FIND DECIMAL EQUIVALENT & RANKING THE MATRIX IN COLUMN WISE
• Assign Binary number for corresponding row – Bottom to Top
• Find Decimal Value – Row 1 = ( 1 × 26 ) + ( 1 × 25 )
= 64 + 32 = 96
MACHINES
PARTS
A B C D E F G H I BINARY
VALUES
1 1 1 1 26
5 1 1 25
7 1 1 1 24
4 1 1 23
3 1 1 1 22
6 1 1 21
2 1 1 20
DECIMAL
EQUIVALENT
96 24 6 64 5 24 16 96 7
RANK 1 4 8 3 9 5 6 2 7

5. REORDER THE COLUMNS IN THE PART MACHINE INCIDENCE MATRIX
• Reorder the columns in the part machine incidence matrix by listing them in
decreasing order starting with left column.
PART FAMILY 1 – (A, H, D) & (1 & 5) PART FAMILY 2 – (B, F, G) & (7 & 4)
PART FAMILY 3 – (I, C, E) & (3, 6 & 2)
MACHINES
PARTS
A H D B F G I C E
1 1 1 1
5 1 1
7 1 1 1
4 1 1
3 1 1 1
6 1 1
2 1 1

INTRODUCTION TO CELLULAR MANUFACTURING
• Cellular Manufacturing is an application of group technology in which
dissimilar machines or processes have be aggregated into cells,
➢ each of which is dedicated to the production of a part or product family
or a limited group of families.
BENEFITS OF CELLULAR MANUFACTURING

• A Composite Part for a given family, which includes all of the design and
manufacturing attributes of the family.
• In general, an individual part in the family will have some of the features that
characterize the family but not all of them. The composite part possesses all of the
features

MACHINE CELL DESIGN
• Design of the machine cell is critical in cellular manufacturing.
• The cell design determines to a great degree the performance of the
cell.
• GT manufacturing cells can be classified according to the number of
machines and the degree to which the material flow is mechanized
between machines.
• Four common GT cell configurations:
1. Single machine cell
2. Group machine cell with manual material handling
3. Group machine cell with semi-integrated handling
4. Flexible manufacturing cell or flexible manufacturing system
1. TYPES OF MACHINE CELLS AND LAYOUTS

MACHINE CELL DESIGN
• Single machine cell consists of one machine plus supporting fixtures and
tooling.
• This type of cell can be applied to work parts whose attributes allow them
to be made on one basis type of process, such as turning or milling.

MACHINE CELL DESIGN
• Group machine cell with manual handling is an arrangement of more
than one machine used collectively to produce one or more part families.
• There is no provision for mechanized parts movement between the
machines in the cell.
• Instead, the human operators who run the cell perform the material handling
function. The cell is often organized into a U-shaped layout.
U-shaped
Layout

MACHINE CELL DESIGN
• Group machine cell with semi-integrated handling uses a mechanized handling
system, such as a conveyor, to move parts between machines in the cell.
In-line Layout
Loop Layout
Rectangular
Layout

• Flexible Manufacturing System combines a fully integrated material
handling system with automated processing stations.
• The FMS is the most highly automated of the Group Technology machine
cells.
MACHINE CELL DESIGN
In-line Layout
Loop Layout
Rectangular
Layout

MACHINE CELL DESIGN
2- TYPES OF PART MOVEMENTS
• Determining the most appropriate cell layout depends on the routings of
parts produced in the cell.
• Four types of part movement can be distinguished in a mixed model part
production system.
1. Repeat Operation, in which a
consecutive operation is carried out
on the same machine, so that the
part does not actually move.
2. In-sequence move, in which the
part move from the current machine
to an immediate neighbor in the
forward direction.
3. By-passing move, in which the part moves forward from the current machine to
another machine that is two or more machines ahead.
4. Backtracking move, in which the part moves from the current machine in the
backward direction to another machine.

MACHINE CELL DESIGN

ARRANGING MACHINES IN A GT CELL
• After part-machine grouping have been identified by rank order clustering,
the next problem is to organize the machines into the most logical
arrangement.
HOLLIER METHOD. This method uses the sums of flow “From” and “To” each
machine in the cell. The method can be outlined as follows
1. Develop the From-To chart from part routing data. The data contained in the
chart indicates numbers of part moves between the machines in the cell.
2. Determine the “From” and “To” sums for each machine. This is accomplished
by summing all of the “From” trips and “To” trips for each machine.
➢ The “From” sum for a machine is determined by adding the entries in the
corresponding row.
➢ The “To” sum is found by adding the entries in the corresponding column.
1. GROUPING PARTS AND MACHINES INTO FAMILIES. – RANK
ORDER CLUSTER ANALYSIS
2. ARRANGING MACHINES IN A GT CELL. – HOLLIER METHOD

3. Determine the From/To ratio for each machine.
4. Arrange machines in order of decreasing From/To ratio.
➢ Machines with a high From/To ratio distribute more work to other
machines in the cell but receives less work from other machines.
➢ Machines with low From/TO ratio receive less work from other
machines
➢ Machines with High From/To ratios are placed at the beginning of the
work flow.
➢ Machines with low From/To ratios are placed at the ed of the work
flow.
IN CASE OF A TIE,
➢ The machines with higher From values is placed ahead of the
machine with lower value.
ARRANGING MACHINES IN A GT CELL

EXAMPLE OF ARRANGING MACHINES IN A GT CELL
• Suppose that four machines, 1, 2, 3, and 4 have been identified as
belonging in a GT machine cell. An analysis of 50 parts processed on
these machines has been summarized in the From-To chart presented
below. Additional information is that 50 parts enter the machine
grouping at machine 3, 20 parts leave after processing at machine 1,
and 30 parts leave after machine 4. Determine a logical machine
arrangement using Hollier method.

EXAMPLE OF ARRANGING MACHINES IN A GT CELL
• The resulting machine sequence 3 ➔ 2 ➔ 1 ➔ 4

HOLLIER METHOD
Resulting
machine
sequence
3 – 2 – 1 – 4
The number of in-sequence moves = 40 + 30 + 25 = 95
The number of Bypassing moves = 10 + 15 = 25
The number of Backtracking moves = 5 + 10 = 15
The total number of moves = 135
a) Percentage of in-sequence moves = 95/135 = 0.704 = 70.4 %
b) Percentage of Bypassing moves = 25/135 = 0.185 = 18.5 %
c) Percentage of Backtracking moves = 15/135 = 0.111 = 11.1%

FMS – FLEXIBLE MANUFACTURING SYSTEM
• Flexibility measures the ability to adapt “to a wide range of possible
environment”.
• To be flexible, a manufacturing system must posses the following capabilities:
➢ The ability to identify & distinguish among the different incoming parts
processed by the system.
➢ Quick changeover of operating instructions to the computer controlled
production machines.
➢ Quick changeover of physical setups of fixtures, tools and other working units.
• This capabilities are very difficult to achieve through manually operated
manufacturing systems.
• An automated system assisted with sensor system is required to accomplish
the needs and requirements of industry.
• Flexible manufacturing system has come up as a viable mean to achieve these
prerequisites.
• A flexible manufacturing system (FMS) is a highly automated GT machine
cell, consisting of a group of processing work stations, interconnected by
an automated material handling & storage system, & controlled by a
distributed computer system.

FLEXIBILITYBASIC FLEXIBILITIES
MACHINE FLEXIBILITY:
• The various types of operations that the machine can perform without requiring prohibitive
effort in switching from one operation to another.
MATERIAL HANDLING FLEXIBILITY:
• It means, different part types can be transported and properly positioned at the various
machine tools in a system.
OPERATION FLEXIBILITY:
• It means, alternative operation sequences can be used for processing a part type.
• It is the ability to interchange the sequence of manufacturing operations for a given part.
AGGREGATE FLEXIBILITIES
PROGRAM FLEXIBILITY:
• The ability of a system to run for reasonably long periods without external intervention.
PRODUCTION FLEXIBILITY:
• The volume of the set of part types that a system can produce without major investment in
capital equipment.
MARKET FLEXIBILITY:
• The ability of a system to efficiently adapt to changing market conditions.

FLEXIBILITY - SYSTEM FLEXIBILITIES
VOLUME FLEXIBILITY:
• A measure of a system's capability to be operated profitably at different volumes of the
existing part types.
• It is the ability to operate profitably at different production volume.
EXPANSION FLEXIBILITY:
• It is the ability to expand the capacity of the system as needed, easily and modularly.
ROUTING FLEXIBILITY:
• A measure of the alternative paths that a part can effectively follow through a system for
a given process plan.
• It is the ability to vary the path a part may take through the manufacturing system.
PROCESS FLEXIBILITY:
• A measure of the volume of the set of part types that a system can produce without
incurring any setup.
• It is the ability to change between the productions of different products with minimal
delay.
PRODUCT FLEXIBILITY:
• It is the ability to change the mix of products in current production, also known as mix-
change flexibility (Carter, 1986).

TYPES OF FMS
DEPENDING UPON KINDS OF OPERATION
PROCESSING OPERATION.
• This operation transforms a work
material from one state to another
moving towards the final desired part or
product.
• It adds value by changing the geometry,
properties or appearance of the starting
materials.
ASSEMBLY OPERATION.
• It involves joining of two or more
component to create a new entity which
is called an assembly/subassembly.
• Permanent joining processes include
welding, brazing, soldering , adhesive
bonding, rivets, press fitting, and
expansion fits.

TYPES OF FMS
DEPENDING UPON NUMBER OF MACHINES
SINGLE MACHINE CELL (SMC)
• It consist of a fully automated machine capable of unattended operations for
a time period longer than one machine cycle.
• It is capable of processing different part styles, responding to changes in
production schedule, and accepting new part introductions.
• In this case processing is sequential not simultaneous.

TYPES OF FMS
FLEXIBLE MANUFACTURING CELL (FMC).
• It consists of two or three processing workstation and a part handling
system.
• The part handling system is connected to a load/unload station.
• It is capable of simultaneous production of different parts.

TYPES OF FMS
FLEXIBLE MANUFACTURING SYSTEM (FMS)
• The idea of an FMS was proposed in England (1960s) under the name
"System 24", a flexible machining system that could operate without human
operators 24 hours a day under computer control.
• At that time, the objective is to focus on automation rather than the
"reorganization of workflow".
• Early FMSs were large and very complex, consisting of dozens of
Computer Numerical Controlled machines (CNC) and sophisticate material
handling systems. – Expensive to Implement.
• Currently, the trend in FMS is toward small versions of the traditional FMS,
called flexible manufacturing cells (FMC).
• Today two or more CNC machines are considered a flexible cell and two or
more cells are considered a flexible manufacturing system.
• A flexible manufacturing system (FMS) is a highly automated GT
machine cell, consisting of a group of processing work stations,
interconnected by an automated material handling & storage system,
& controlled by a distributed computer system. It can handle any
family of parts for which it has been designed and developed.

FLEXIBLE MANUFACTURING SYSTEM (FMS)

TYPES OF FMS
DEPENDING UPON LEVEL OF FLEXIBILITY
FLEXIBILTY CRITERIA (TESTS OF FLEXIBILITY)
SYSTEM TYPE
1. PART VARIETY
TEST
2. SCHEDULE
CHANGE TEST
3. ERROR
RECOVERY
TEST
4. NEW PART
TEST
DEDICATED
FMS
Limited. All parts
known in advance
Limited changes
can be tolerated
Limited by
sequential
processes
No.
New part
introductions
difficult.
RANDOM
ORDER FMS
Yes.
Substantial part
variations
possible.
Frequent &
Significant
changes possible.
More number of
Machine,
minimizes effect
of machine
breakdowns.
Yes.
System designed
for new part
introductions.
• DEDICATED FMS – Instead of being general
purpose, the machines can be designed for
specific processes required to make the
limited part family.
• RANDOM ORDER FMS – General purpose
machines used. Production schedule change
from day to day.

FMS LAYOUT
• The machines and handling system are arranged in a straight line.
• In Figure (a) parts progress from one workstation to the next in a well-defined
sequence with work always moving in one direction and with no back-flow.
• Routing flexibility can be increased by installing a linear transfer system with bi-
directional flow, as shown in Figure (b).
• A secondary handling system is provided at each workstation to separate most of
the parts from the primary line.
• Material handling equipment used: in-line transfer system; conveyor system; or rail-
guided vehicle system.
• Load – Parts
Loading Station
• Unld – Parts
unloading station
• Man – Manual
Station
• Aut – Automated
Station
• Mach – Machining
Station
INLINE - LAYOUT

FMS LAYOUT
• Workstations are organized in a loop that is served by a looped parts handling system.
• In Figure (a) parts usually flow in one direction around the loop with the capability to stop
and be transferred to any station.
• Each station has secondary handling equipment so that part can be brought-to and
transferred from the station work head to the material handling loop.
• Load/unload stations are usually located at one end of the loop.
• An alternative form is the rectangular layout shown in Figure (b). This arrangement allows
for the return of pallets to the starting position in a straight line arrangement
LOOP LAYOUT

FMS LAYOUT
LADDER LAYOUT
• This consists of a loop with rungs upon which
workstations are located.
• The rungs increase the number of possible
ways of getting from one machine to the next,
and removes the need for a secondary material
handling system.
• It reduces average travel distance and
minimizes congestion in the handling system,
thereby reducing transport time between
stations.
RUNGS
ROBOT CENTERED LAYOUT
• This layout uses one or more
robots as the material handling
system.
• The machines are laid out in a
circle, such a layout is called
circular layout.

OPEN-FIELD LAYOUT
• Consists of multiple loops and
ladders.
• This layout is generally used to
process a large family of parts.
• The number of different machine
types may be limited.
• Parts are usually routed to different
workstations—depending on which
one becomes available first.
FMS LAYOUT
Work-in-process (WIP) refers to a
component of a company's
inventory that is partially
completed.
• Rechg – Battery Recharging Station
• AGV – Automatic Guided Vehicle

COMPONENTS OF FMS
➢ Machining Work Stations
❖ CNC machine with Automatic Tool Changer, Automatic Pallet Changer.
➢ Assembly Work Stations
❖ It consist of number of work stations with industrial robots that sequentially assemble
components to the base part to create the overall assembly.
➢ Supporting Work Stations
❖ Inspection Stations – Coordinate Measuring Machine, Machine Vision.
➢ Other Work Stations
❖ In sheet metal industries, Work station – Press Working Operation, Other Work
Station – Punching, Shearing & Bending Process.
❖ In Forging industries – Forging Press, Heating Furnace, Trimming Section
WORK STATIONS
• The processing & assembly equipment used in FMS
depends on the type of work accomplished by the
system.
➢ Load /Unload Work Stations
❖ Physical Interface between the FMS & the rest of
the factory.
❖ Raw materials enter the system & the finished
parts exit the system.

MATERIAL HANDLING & STORAGE SYSTEM
FUNCTIONS
• Allow random, independent movement of work parts between stations
• Parts must be capable of moving from one machine to another machine in the
system, to provide various routing alternatives.
• Enables handling of a variety of work part configurations
• For Rotational parts – Industrial robots are used to load & unload the turning
machine, & to move parts between stations.
• For Non-Rotational Parts – Fixture is used to locate the top face of the pallet & is
designed to accommodate different part configurations.
• Provides temporary storage
• Each machine has a small queue of parts, which helps to maintain high machine
utilization.
• Provides convenient access for loading & unloading work parts
• Creates compatibility with computer control
• The handling system directly controlled by computers to various work station, Load &
Unload station, & Storage areas.
PRIMARY MATERIAL HANDLING SYSTEM – Establishes the Basic Layout, Responsible
for moving parts between stations in the system.
SECONDARY MATERIAL HANDLING SYSTEM – To transfer the parts from primary
system to the work stations. Transfer devices, Automatic Pallet Changer.
COMPONENTS OF FMS

• This Distributed Computer System is interfaced to the work stations, Material Handling
Systems & other hardware components.
• It consists of a central computer & micro computers controlling the individual machines &
other components.
• Work station control – Computer controls the individual processing & Assembly stations. CNC
controls the individual machine.
• Distribution of control instructions to work stations – DNC system stores the programs,
allow submission of new program & able to do editing the program. Perform DNC function.
• Production control – Routing the appropriate pallet to load /unload area & providing
instructions to the operator to load the desired work part.
• Traffic control – Management of the primary material handling system that moves parts
between stations.
• Shuttle control – Operation & Control of Secondary Material Handling system at each work
station.
• Workpiece monitoring – The computer must monitor the status of each pallet in the primary &
Secondary handling system.
• Tool Control – Tool location – Keep tracking of tools at each station.
• Tool life monitoring – A record of the machining time usage is maintained for each tool.
• Performance monitoring & Reporting – To collect data on the operation & performance of the
FMS.
• Diagnostics – To reduce the breakdowns & Downtime, to increase the availability of the
system.
COMPUTER CONTROL SYSTEM - FMS

HUMAN RESOURCES
• Humans are needed to manage the operations of the system.
• Loading raw work parts into the system
• Unloading finished parts from the system
• Changing & Setting tools
• Performing Equipment Maintenance & Repair
• Performing NC part programming
• Programming & Operating the computer system
• Managing the system by generating & verifying the reports.
❖Availability – Summary of Uptime of the Work stations. If downtime occurs
means, reason for downtime of the work station.
❖Utilization – Average Utilization of the FMS for specified periods (Days, Week,
Months). Utilization report of each work station.
❖Production – Daily & weekly production counts of the FMS. Compare this with
Production schedule.
❖Tooling – Listing of Tools at each station & Tool life status.
❖Status – Instantaneous snapshot of the present condition of the FMS. Line
supervision can verify the current status of the production.
COMPONENTS OF FMS

FMS PLANNING & IMPLEMENTATION
• Implementation of a FMS requires a major investment & commitment by the company.
• Before implementing the FMS into the organization, the organization must consider the
following issues.
ISSUES DESCRIPTION
Part Family
Considerations
Any flexible manufacturing system must be designed to process a limited
range of part or product styles.
1. The part family can be processed on the FMS must be defined.
2. Composite Part Concept – Different components (Features) used on
the Same product.
Processing
Requirements
1. The entire range of possible parts to be processed are know.
2. Use this information to help choose associated processing
requirements for each part.
• Rotational Part – Turning Centers
• Non-Rotational parts – Milling Centers
Physical
Characteristics of
the Work parts
1. Size and weight of work parts determine size of the machines required
to process the parts.
2. It also determines the size of the material handling system needed.
Production Volume 1. Quantities to be produced are known.
2. Requirement – How many machines required? – What kind of material
handling system needed?
PLANNING ISSUES FOR FMS

FMS PLANNING & IMPLEMENTATION - DESIGN ISSUES FOR FMS
ISSUES DESCRIPTION
Types of
workstations
• Workstation choices have to be made, depending on part processing
requirements.
• Consider position and use of load and unload stations also.
Variations in
process routings
and FMS layout
• Part processing variations are minimal - Use an in-line flow layout
• Part processing variations are high - Loop layout, Open field layout.
Material handling
system
• Based on the layout, we must choose appropriate primary and
secondary material handling system.
Work-in-process
and storage
capacity
• Determining an appropriate level of WIP allowed is important, as it
affects the level of utilization and efficiency of the FMS.
• Storage capacity must be compatible with the level of WIP chosen.
Tooling
• Determine the number and type of tools required at each workstation.
• How much duplication of tooling should occur at workstations?
• Duplication allows for efficient re-routing in the system should
breakdowns occur
Pallet fixtures
• For non-rotational parts - Selection of a few types of pallet fixtures is
important.
• Factors that influence the decision include: levels of WIP chosen, and
differences in part style and size.

FMS PLANNING & IMPLEMENTATION
OPERATIONAL ISSUES FOR FMS
ISSUE DESCRIPTION
Scheduling
and
Dispatching
• Based upon the Master Production Schedule, Scheduling must be done.
• Dispatching the parts into the system at the appropriate times.
Machine
loading
• This problem is concerned with allocating the operations & tooling resources
among the machines in the system to accomplish the required production
schedule.
Part routing • Routing decisions involve selecting the routes that should be followed by
each part in the production mix in order to maximize use of work station
resources.
Part grouping • Part types must be grouped for simultaneous production, given limitations on
available tooling and other resources at workstations.
Tool
management
• Managing the available tools involves making decisions on when to change
tools & how to allocate tooling to work stations in the system.
Pallet and
fixture
allocation
• How do we allocate specific pallets and fixtures to certain parts to be
launched into the system?
• Different parts require different pallet fixtures, and before a given part style
can be launched into the system, a fixture for that part must be made
available

QUANTITATIVE ANALYSIS OF
FLEXIBLE MANUFACTURING SYSTEMS
Average Work Load for Station i
• WLi = σ𝑖 σ 𝑘 𝑡𝑖𝑗𝑘 𝑓𝑖𝑗𝑘 𝑃𝑗
Mean Number of Transports
• nt = σ𝑖 σ 𝑗 σ 𝑘 𝑓𝑖𝑗𝑘 𝑃𝑗 − 1
Work Load of Handling System (min)
• WLn+1 = nt tn+1
Maximum Production Rate of all parts produced by the system
• 𝑅 𝑝
∗ =
𝑠∗
𝑊𝐿∗ WL* - Work load at Bottleneck Station (pc/min)
• s* - Number of servers at Bottleneck Station
Utilization of Station i
• Ui =
𝑊𝐿𝑖
𝑆𝑖
(𝑅 𝑝
∗ ) =
𝑊𝐿𝑖
𝑆𝑖
.WLi
Number of Busy Servers at each station i
• BSi = WLi (𝑅 𝑝
∗
) = WLi .
𝑠∗
𝑊𝐿∗

A flexible manufacturing cell consists of two machining workstations plus a load/unload station.
Station 1 is the load /unload station. Station 2 performs milling operations & consists of one
server (one milling machine). Station 3 has one server that performs drilling (one CNC drill
press). The three stations are connected by a part handling system that has one work carrier. The
mean transport time is 2.5 min. The FMC produces three parts, A, B & C. The part mix fractions &
process routing for the three parts presented in the table below.
The operation frequency Fijk = 1.0 for all operations.
Determine (a) Maximum production rate of the FMS (b) Corresponding Production Rate of each
product (c) Utilization of each station and (d) Number of busy servers at each station.
WLi = σ𝒊 σ 𝒌 𝒕𝒊𝒋𝒌 𝒇𝒊𝒋𝒌 𝑷𝒋
• WL1 = (3 + 2) (1.0) (0.2) + (3 + 2) (1.0)
(0.3) + (3 + 2) (1.0) (0.5) = 5.0 min
• WL2 = ( 20 ) (1.0) (0.2) + ( 15 ) (1.0) (0.3)
+ ( 22 ) (1.0) (0.5) = 19.5 min
• WL3 = ( 12 ) (1.0) (0.2) + ( 30 ) (1.0) (0.3)
+ ( 14 ) (1.0) (0.5) = 18.4 min
Moves Between Station, nt = 3,
WLn+1 = nt tn+1
• WL4 = 3 ( 2.5 ) = 7.5 min
SOLUTION
(a) Compute the FMS Max. production rate, First find Work loads(WL) at each station

Work load per server (WLi/si) - si – Number of servers at workstation i
At Station 2,
Maximum Production Rate 𝑹 𝒑
∗
=
𝒔∗
𝑾𝑳∗ ,
𝟏
𝟏𝟗.𝟓
= 0.05128 pc/min = 3.077 pc/hr.
(b) To determine production rate of each product
Individual Part Production Rate , 𝑹 𝒑𝒋
∗
= Pj (𝑹 𝒑
∗ )
𝑹 𝒑𝑨
∗
= Pj (𝑹 𝒑
∗
) = Pj (
𝒔∗
𝑾𝑳∗) = (0.2) ( 0.05128 ) = 0.01026 pc/min = 0.6154 pc/hr
𝑹 𝒑𝑩
∗
= Pj (𝑹 𝒑
∗
) = Pj (
𝒔∗
𝑾𝑳∗) = (0.3) ( 0.05128 ) = 0.01538 pc/min = 0.9231 pc/hr
𝑹 𝒑𝑪
∗
= Pj (𝑹 𝒑
∗ ) = Pj (
𝒔∗
𝑾𝑳∗) = (0.5) ( 0.05128 ) = 0.02564 pc/min = 1.5385 pc/hr
STATION WLi/si
1(Load/Unload) 5.0/1 = 5.0 min
2(Mill) 19.5/1 = 19.5 min
3(Drill) 18.4/1 = 18.4 min
4(Material Handling) 7.5/1 = 7.5 min
• Bottleneck station has largest WLi/si
ratio
• Second Station – Milling = Bottleneck
Station

(c) UTILIZATION of each station Ui =
𝑾𝑳𝒊
𝑺𝒊
(𝑹 𝒑
∗ )
• U1 = ( 5.0 / 1 ) ( 0.05128 ) = 0.256 = 25.6 %
• U2 = ( 19.5 / 1 ) ( 0.05128 ) = 1.0 = 100 %
• U3 = ( 5.0 / 1 ) ( 0.05128 ) = 0.944 = 94.4 %
• U4 = ( 5.0 / 1 ) ( 0.05128 ) = 0.385 = 38.5 %
(d) Mean number of busy servers at each station, BSi = WLi (𝑹 𝒑
∗ )
• BS1 = ( 5.0 ) ( 0.05128 ) = 0.256 servers
• BS2 = ( 19.5 ) ( 0.05128 ) = 1.0 servers
• BS3 = ( 18.4 ) ( 0.05128 ) = 0.944 servers
• BS4 = ( 7.5 ) ( 0.05128 ) = 0.385 servers

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