CIM 15ME62 Module-1

Course:
Computer Integrated Manufacturing
Course Code: 15ME62
University: Visvesvaraya Technological University
Academic Year: 2018-19
1

Important Texts and References
• Automation, Production Systems and Computer-Integrated Manufacturing,
by Mikell P Groover, 4th Edition, 2015, Pearson Learning.
• Principles of Computer Integrated Manufacturing, S. Kant Vajpayee, 1999,
Prentice Hall of India, New Delhi (preferably latest edition).
• Internet of Things (IoT): Digitize or Die: Transform your organization.
Embrace the digital evolution. Rise above the competition, by Nicolas
Windpassinger, Amazon.
• Additive Manufacturing Technologies: Rapid Prototyping to Direct Digital
Manufacturing, 2nd Ed. (2015), Ian Gibson, David W. Rosen, Brent Stucker
• Industry 4.0: The Industrial Internet of Things, Apress, 2017, by Alasdair
Gilchrist
• Internet of Things: A Hands-on Approach, by Arshdeep Bahga and Vijay
Madisetti (Universities Press), 2011
• Understanding Additive Manufacturing, Andreas Gebhardt, Hanser Publishe
2

Chapter – 1
Introduction to CIM and
Automation
3

Manufacturing:
• Application of Physical and
Chemical processes to alter
the geometry, properties,
and/or appearance of a given
starting material to make
parts or products.
Present challenges??
4

• Present challenges??
• Criteria to be in market –
– Price
– Quality
– Delivery speed
– Innovation ability
• Result??
– Criteria understood and executed better than
competitor, market share is increased.
5

• How the criteria are met??
– Setup time or time required to get a machine ready for
production ----??
– Quality or % of defective parts produced ---??? or % of
total sales
– Manufacturing space ratio (-- or a measure of how
efficiently manufacturing space is utilized)
– Inventory: Velocity/residence time
– Flexibility or a measure of the number of different parts
that can be produced on the same machine
– Distance or total linear feet of a part’s travel through the
plant from raw material in receiving to finished products
in shipping
6

Information-processing cycle in a typical manufacturing firm
7

• The criteria are met through:
• Computer Integrated Manufacturing
8

Module 1: Introduction to CIM and Automation
• Computer Integrated Manufacturing
– Process of automating various functions in a
manufacturing company (business, engineering, and
production) by integrating the work through computer
networks and common databases. CIM is a critical
element in the competitive strategy of global
manufacturing firms because it lowers costs, improves
delivery times and improves quality.
– It is the computerization of the entire business
enterprise.
9

Module 1: Introduction to CIM and Automation
Is CIM a concept or a technology?
• CIM is both a concept and a technology.
• For top management, CIM is a concept, a blueprint for
success.
• For middle management and line managers, CIM is a
technology, a physical realization of resources that are
more capable and flexible.
- Kant Vajpayee and Reiden
10

Elements (integrated into a whole) of CIM.
• Product design
• Manufacturing planning
• Manufacturing control
• Business planning and support
11

Computerized elements of a CIM system
12

Core or Base Elements in a CIM System
Devices / Machine Tools / Equipment:
• CNC, Computer numerical controlled machine tools
• DNC, Direct numerical control machine tools
• PLCs, Programmable logic controllers
• Robots
• Computers
• Software
• Controllers
• Networks
• Interfacing
• Monitoring equipment
13

Technologies:
• FMS - Flexible Manufacturing System
• ASRS – Automated Storage and Retrieval System
• AGVs – Automated Guided Vehicles
• Robotics
• Automated conveyor systems
14

CAD/CAM
• A term that denotes a technology where computers are
used to perform certain functions in design and
manufacturing.
• CAD – use of computer systems to assist in the creation,
modification, analysis or optimization of a design.
• CAM - use of computer systems to plan, manage, and
control the operations of a manufacturing unit or a shop
floor through either direct or indirect computer interface with
the plant’s production resources.
15

CAD/CAM and CIM
16

Benefits of CIM
Integration of technologies brings following benefits:
• Creation of a truly interactive system that enables
manufacturing functions to communicate easily with
other relevant functional units.
• Accurate data transferability among manufacturing
plant or subcontracting facilities at implant or diverse
locations.
• Faster responses to data‐changes for manufacturing
flexibility.
• Increased flexibility towards introduction of new
products.
• Improved accuracy and quality in the manufacturing
process.
17

Benefits of CIM
• Improved quality of the products.
• Control of data‐flow among various units and
maintenance of user‐library for system‐wide data.
• Reduction of lead times which generates a
competitive advantage.
• Streamlined manufacturing flow from order to
delivery.
• Easier training and re‐training facilities.
18

Automation in Production Systems
– Automation is the technology by which a process or
procedure is accomplished without human assistance. It
is implemented using a program of instructions
combined with a control system that executes the
instructions (eg., ??)
– Coined in 1946 by Mr. Del Harder, an engineering
manager at FMC, to refer to the variety of automatic
transfer devices and feed mechanisms that had been
installed in Ford’s production plants.
A manufacturing system is a logical grouping of equipment in the factory and the worker(s) who
operate(s) it. Examples include worker-machine systems, production lines, and machine cells.
A production system is a larger system that includes a collection of manufacturing systems and the
support systems used to manage them. A manufacturing system is a subset of the production system.19

The elements of the production system that can be
automated
- Automation, Production Systems, and CIM, M P Groover, PHI, 2015, pp. 23
The physical facilities of the production
system include the equipment, the way
the equipment are laid out, and the
factory in which the equipment are
located.
Procedures used by the company to
manage production and to solve the
technical and logistics problems
encountered in ordering materials,
moving the work through the factory,
and ensuring that products meet
quality standards.
20

• Examples of automated manufacturing
systems
• Automated machine tools that process parts
• Transfer lines that perform a series of machining operations
• Automated assembly systems
• Manufacturing systems that use industrial robots to perform
processing or assembly operations
• Automatic material handling and storage systems to
integrate manufacturing operations
• Automatic inspection systems for quality control.
21

Three Basic Elements of an Automated System
• Power to accomplish the process and operate the system,
• A program of instructions to direct the process, and
• A control system to actuate the instructions.
22

• Types of automated manufacturing systems
• Fixed automation
• Programmable automation, and
• Flexible automation.
23

Fixed automation
• A system in which the sequence of processing (or
assembly) operations is fixed by the equipment
configuration.
• Typical features of fixed automation are
– High initial investment for custom-engineered equipment,
– High production rates,
– Inflexibility of the equipment to accommodate product variety.
24

Programmable Automation
• The production equipment is designed with the capability to
change the sequence of operations to accommodate
different product configurations.
• The operation sequence is controlled by a program, which
is a set of instructions coded so that they can be read
and interpreted by the system. New programs can be
prepared and entered into the equipment to produce new
products.
• Features of programmable automation include:
– high investment in general-purpose equipment,
– lower production rates than fixed automation,
– flexibility to deal with variations and changes in product
configuration,
– high suitability for batch production.
25

• Examples of programmable automation numerically
controlled (NC) machine tools, industrial robots, and
programmable logic controllers.
• The parts or products are typically made in batches.
• To produce each new batch of a different item, the system
must be reprogrammed with the set of machine
instructions that correspond to the new item.
• The physical setup of the machine may also be changed,
tools must be loaded, fixtures must be attached to the
machine table, and any required machine settings must
be entered.
26

Flexible Automation
• It is an extension of programmable automation.
• This system is capable of producing a variety of parts or
products with virtually no time lost for changeovers from
one design to the next.
• Features of flexible automation include:
– high investment for a custom-engineered system,
– continuous production of variable mixtures of parts or
products,
– medium production rates,
– flexibility to deal with product design variations.
• Examples of flexible automation are flexible manufacturing
systems that perform machining processes.
27

Levels of Automation
Automated systems can be applied to various levels of factory
operations.
28

• Mechanization and Automation
• Mechanization refers to the use of machinery (usually
powered) to assist or replace human workers in performing
physical tasks, but human workers are still required to
accomplish the cognitive and sensory elements of the
tasks.
• Automation refers to the use of mechanized equipment
that performs the physical tasks without the need for
oversight (supervision) by a human worker.
29

Reasons for Automation
• Increase labor productivity: Automating a manufacturing
operation invariably increases production rate and labor
productivity. This means greater output per hour of labor input.
• Reduce labor cost: Higher investment in automation has
become economically justifiable to replace manual operations.
Machines are increasingly being substituted for human labor to
reduce unit product cost.
• Mitigate the effects of labor shortages: Shortage of labor in
many nations has stimulated the development of automated
operations as a substitute for labor.
• Reduce or eliminate routine manual and clerical tasks: An
argument can be put forth that there is social value in automating
operations that are routine, boring, fatiguing, and possibly
irksome. Automating such tasks improves the general level of
working conditions.
30

• Improve worker safety: Automating a given operation and transferring
the worker from active participation in the process to a monitoring role,
or removing the worker from the operation altogether, makes the work
safer. The safety and physical well-being of the worker has become a
national objective with the enactment of the Occupational Safety and
Health Act (OSHA). This has provided an impetus for automation.
• Improve product quality: Automation performs the manufacturing
process with greater consistency and conformity to quality
specifications.
• Reduce manufacturing lead time: Automation helps reduce the
elapsed time between customer order and product delivery, providing a
competitive advantage to the manufacturer for future orders. By
reducing manufacturing lead time, the manufacturer also reduces work-
in-process inventory.
31

• Accomplish processes that cannot be done manually: Certain operations
cannot be accomplished without the aid of a machine. These processes
require precision, miniaturization, or complexity of geometry that cannot be
achieved manually. Examples include certain integrated circuit fabrication
operations, rapid prototyping processes based on computer graphics (CAD)
models, and the machining of complex, mathematically defined surfaces using
computer numerical control. These processes can only be realized by
computer-controlled systems.
• Avoid the high cost of not automating: The benefits of automation often are
in the form of improved quality, higher sales, better labor relations, and better
company image. Companies that do not automate are likely to find
themselves at a competitive disadvantage with their customers, their
employees, and the general public.
32

Reasons for not Automating
• Task is technologically too difficult to automate
• Short product life cycle
• Customized product
• Ups and downs in demand
• Need to reduce risk of product failure
• Lack of capital
33

Automation Principle and Strategies
• The USA Principle
• Ten Strategies for Automation and Process Improvement
• Automation Migration Strategy
34

Automation Principle and Strategies
1. Understand the Existing Process
– Input/output analysis
– Value chain analysis
– Charting techniques and mathematical modeling
2. Simplify the process:
– Reduce unnecessary steps and moves
3. Automate the process:
– Ten strategies for automation and production
systems
– Automation migration strategy
35

Ten Strategies for Automation and Process
Improvement
1. Specialization of operations
2. Combined operations
3. Simultaneous operations
4. Integration of operations
5. Increased flexibility
6. Improved material handling and storage
7. On-line inspection
8. Process control and optimization
9. Plant operations control
10.Computer-integrated manufacturing
36

• Specialization of operations (Reduce To)
Involves the use special purpose equipment designed to perform
one operation with the greatest possible efficiency. This is
analogous to the concept of labor specialization, which has been
employed to improve labor productivity.
• Combined operations (Reduce, nm, Th, Tno, Tsu)
Production occurs as a sequence of operations. Complex parts
may require dozens, or even hundreds, of processing steps. This
strategy involves reducing the number of distinct production
machines or workstations through which the part must be routed.
• Simultaneous operations (Reduce, nm, Th, Tno, Tsu, To)
A logical extension of the combined operations strategy is
to perform at the same time the operations that are
combined at one workstation. In effect, two or more
processing (or assembly) operations are being performed
simultaneously on the same workpart, thus reducing total
processing time.
37

Automation Migration Strategy for Introduction of New
Products
1. Phase 1 – Manual production:
– Single-station manned cells working independently.
– Advantages: quick to set up, low-cost tooling.
2. Phase 2 – Automated production:
– Single-station automated cells operating
independently.
– As demand grows, automation can be justified.
3. Phase 3 – Automated integrated production:
– Multi-station system with serial operations and
automated transfer of work units between stations.
38

Is there a place for manual labor in the modern
production system?
• Two aspects:
1. Manual labor in factory operations
2. Labor in manufacturing support systems
39

• Manual Labor in Factory Operations
• When is manual labor justified?
– Some countries have very low labor rates and
automation cannot be justified.
– Task is technologically too difficult to automate
– Customized product requires human flexibility.
– To cope with ups and downs in demand.
– To reduce risk of new product failure.
40

• Labor in Manufacturing Support Systems
• Product designers who bring creativity to the design
task.
• Manufacturing engineers who:
– Design the production equipment and tooling.
– Plan the production methods and routings.
• Equipment maintenance.
• Programming and computer operation.
• Engineering project work.
• Plant management.
41

Manufacturing Models and Metrics:
• Metrics are those parameters that are used to measure
…….
• Quantitative metrics provide a company with the
means:
– To track performance in successive periods.
– To tryout new technologies and new systems to determine
their merits, identify problems with performance.
– To compare alternative methods and to make good decisions.
• Manufacturing metrics can be divided into 2 basic
categories:
– Production performance measures or metrics
– Manufacturing costs
42

Production Performance Metrics:
• Cycle time, Tc
• Production rate, Rp
• Availability, A
• Production capacity, PC
• Utilization, U
• Manufacturing lead time, MLT
• Work-in-progress, WIP
43

Operation Cycle Time or Cycle Time
• Typical cycle time for a production operation:
Tc = To + Th + Tth
where,
• Tc = cycle time
• To = processing time for the operation
• Th = handling time (e.g., loading and unloading the
production machine), and
• Tth = tool handling time (e.g., time to change tools)
44

Production Rate
Batch production:
Batch time, Tb = Tsu + QTc
Average production time per work unit, Tp = Tb/Q
Production rate, Rp = 1/Tp
Job shop production:
For Q = 1, Tp = Tsu + Tc
For quantity high production:
Rp = Rc = 60/Tp since Tsu/Q  0
Tsu – Setup time; Q –
Batch quantity;
45

• Types of Production
46

Availability (A)
• A common measure of reliability of an equipment (or
proportion uptime of the equipment)


MTBF MTTR
A
MTBF
where MTBF = mean time between failures, and
MTTR = mean time to repair
47

Availability (A)
48

Utilization
• Proportion of time that a productive resource (e.g., a
production machine) is used relative to the time
available. OR
• Amount of output of a production facility relative to its
capacity.
• U = Q/PC, where, Q – actual quantity produced by a
facility during a given time period (pc/week); PC –
production capacity for the same period (pc/week).
• Utilization can be assessed for the entire plant / any
other productive resources(i.e., labor).
• Usually expressed in %.
49

Production Capacity
• The maximum rate of output that a production facility (or
production line, or group of machines) is able to produce
under a given set of assumed operating conditions.
• When referring to a plant or factory, the term plant capacity is
used.
• Assumed operating conditions refer to:
– Number of shifts per day
– Number of hours per shift
– Employment levels
• PC = n SwHs Rp , where,
n - production machines in the plant and they all produce the
same part or product; Sw- number of shifts per period
(shifts/week); - hours / shift; Rp – hourly production rate of
each work center (output units / hr)
50

Manufacturing Lead Time (MLT):
• The total time required to process a given part or product
through the plant, including any time for delays, material
handling, queues before machines, etc.
MLT = no (Tsu + QTc + Tno) where
• MLT = manufacturing lead time
• no = number of operations
• Tsu = setup time
• Q = batch quantity
• Tc = cycle time per part, and
• Tno = non-operation time
51

Work - in - Process(WIP):
• The quantity of parts or products currently located in the
factory that either are being processed or are between
processing operations.
WIP = Rpph (MLT), where
• WIP = work-in-process, pc
• Rpph = hourly plant production rate, pc/hr;
• MLT = manufacturing lead time, hr
52

Problems on Performance metrics
• (1) The automatic lathe department has five machines,
all devoted to the production of the same product. The
machines operate two 8-hr shifts, 5 days/week, 50
weeks/year. Production rate of each machine is 15
units/hr. Determine the weekly production capacity of the
automatic lathe department.
• Solution
PC = n SwHs Rp
= 5 *10*8*15
= 6000 pc/week
53

• (2) A certain part is produced in batch sizes of 100 units.
The batches must be routed through five operations to
complete the processing of the parts. Average setup time
is 3.0 hr/batch, and average operation time is 6.0 min/pc.
Average non-operation time is 7.5 hr for each operation.
Determine the manufacturing lead time to complete one
batch, assuming the plant runs 8 hr/ day, 5 days/wk.
• Solution:
MLT = no (Tsu + QTc + Tno), where, no - No. of operations = 5
Tsu = setup time = 3 hr / batch
Q = batch quantity = 100
Tc = cycle time per part = 6 min/pc
Tno = non-operation time = 7.5 hr/operation
54

MLT = no (Tsu + QTc + Tno)
= 5 {3 + 100 (6/60) + 7.5} = 102.5 hr
At 8 hr/day, this amounts to 102.5/8 = 12.81 days
Problem
• (3) Average batch quantity = 100 units, average setup
time = 3.0 hr per batch, number of operations per batch
= 5, and average operation time is 6.0 min per piece for
the population of parts made in the plant. Non-operation
time = 7.5 hr. The plant has 20 production machines that
are 100% utilized (setup and run time), and it operates
40 hr/wk. Determine (a) weekly plant production rate and
(b) work-in-process for the plant.
55

• Solution:
MLT = no (Tsu + QTc + Tno), where, - No. of operations, no = 5
Tsu = setup time = 3 hr / batch
Q = batch quantity = 100
Tc = cycle time per part = 6 min/pc
Tno = non-operation time = 7.5 hr/operation
• We know, Batch time, Tb = Tsu + QTc
Therefore, Tb = 3 + 100 (6/60) = 13 hr
• Average production time per work unit, Tp = Tb/Q
Hence, Tp = 13/100 = .13 hr or 7.8 min.
• The hourly production rate, Rp is given by 60 / Tp.
Hence, Rp = 60/7.8 = 7.69 pc/hr for each machine.
56

• Weekly production rate for the plant can be determined
by using this average value of production rate per
machine and by the following equation:
where, Rpph = hourly plant production rate, pc/hr
n = number of production machines
Hence, Rpph = 20 (7.69/5) = 30.77 pc/hr
And, Rppw = 40(30.77) = 1,231 pc/wk
57

• Solution:
(b) Given U = 100% = 1.0
Hence, WIP = Rpph(MLT) = 30.77(102.5) = 3,154 pc
58

• (4) A certain part is routed through six machines (operations) in a
batch production plant. The setup and operation times for each
machine are given in the table below. The batch size is 100 and the
average non-operation time per machine is 12 hours. Determine (a)
manufacturing lead time and (b) production rate for operation 3.
Machine Setup time
(hr.)
Cycle time
(min.)
1 4 5.0
2 2 3.5
3 8 10.0
4 3 1.9
5 3 4.1
6 4 2.5
59

• Solution
• Average Tsu = (4 + 2 + 8 + 3 + 3 + 4)/6 = 24/6 = 4.0 hr
• Average Tc = (5 + 3.5 + 10 + 1.9 + 4.1 + 2.5)/6 = 27/6 =
4.5 min
(a) MLT = 6(4.0 + 100(4.5/60) + 12) = 6(23.5) = 141 hr
(b) Rp for operation 3: Tp = [8.0 + 100(10/60)]/100 =
24.67/100 = 0.2467 hr/pc
Hence, Rp = 4.05 pc/hr
(c) Average production rate
Tp = [4.0 + 100(4.5/60)]/100 = 11.5/100 = 0.115 hr/pc
Hence, Rp = 1/0.115 = 8.69 pc/hr
60

Problem:
• (5) The part produced in a certain batch manufacturing
plant must be processed sequentially through six
operations on average. Twenty (20) new batches of parts
are launched each week. Average operation time = 6
min., average setup time = 5 hours, average batch size =
25 parts, and average non-operation time per batch = 10
hr/machine. There are 18 machines in the plant working
in parallel. Each of the machines can be set up for any
type of job processed in the plant. The plant operates an
average of 70 production hours per week. Scrap rate is
negligible. Determine (a) manufacturing lead time for an
average part, (b) plant capacity, (c) plant utilization. (d)
How would you expect the non-operation time to be
affected by the plant utilization?
61

Solution:
(a) MLT = 6(5 + 25(0.1) + 10) = 105 hr
(b) Tp = (5 + 25 x 0.1)/25 = 0.30 hr/pc, Rp = 3.333
pc/hr.
PC = 70(18)(3.333)/6 = 700 pc/week
(c) Parts launched per week = 20 x 25 = 500 pc/week.
Utilization U = 500/700 = 0.7143 = 71.43%
(d) As utilization increases towards 100%, we would
expect the non-operation time to increase. When
the workload in the shop grows, the shop becomes
busier, but it usually takes longer to get the jobs out.
As utilization decreases, we would expect the non-
operation time to decrease.
62

• (6) One million units of a certain product are to be
manufactured annually on dedicated production machines
that run 24 hours per day, five days per week, 50 weeks per
year. (a) If the cycle time of a machine to produce one part is
1.0 minute, how many of the dedicated machines will be
required to keep up with demand? Assume that availability,
utilization, worker efficiency = 100%, and that no setup time
will be lost. (b) Solve part (a) except that availability = 0.90.
• Solution:
• (a) Reqd. parts = 1,000,000; Reqd. time to produce = (1
min/60) = 16,666.7 hr/yr
• Hours available/machine = 24 x 5 x 50 = 6000 hr/yr per
machine
• Number of machines, n = (16,666.6 / 6000) = 2.78  3
machines
• (b) At A = 90%, n = = 3.09  4 machines
63

Chapter – 2
Automated Production Lines
and Assembly Systems
64

• An automated production line consists of multiple workstations
that are automated and linked together by a work handling
system that transfers parts from one station to the next.
General configuration of an automated production line
Proc = processing operation, Aut = automated workstation
65

• Characteristics
• Difficult to alter the sequence and content of the processing
operations once the line is built.
• Automated production lines are examples of fixed automation.
• Application appropriate under the conditions:
 High demand, requiring high production quantities.
 Stable product design (.. where frequent design changes
are difficult to accommodate).
 Multiple operations performed on the product during its
manufacture.
67

• Advantages
• Low amount of direct labor
• Low product cost, because the cost of fixed equipment is
spread over many units
• High production rate
• Minimal work-in-progress and manufacturing lead time
• Minimal use of factory floor space
68

• Work Part Transport
• A system (…of mechanisms) that moves parts between
stations on the line.
• Synchronous (intermittent), asynchronous (power-and-free
transfer) and continuous (rarely) mechanisms.
• Asynchronous mechanisms are more common in automated
production lines because..
– They are more flexible
– They permit queues of parts to form between workstations
to act as storage buffers
– It is easier to rearrange or expand the production line.
• Continuous work transport mechanisms are rarely used due to
the difficulty in providing accurate registration between the
station work heads and the continuously moving parts.
69

• Palletized transfer line
• A transfer line that uses pallet fixtures or similar work-
holding devices.
• A pallet fixture is a work-holding device that is designed
to
– fixture the part in a precise location relative to its base and
– be moved, located, and accurately clamped in position at
successive workstations by the transfer system.
• When Pallet fixtures are used, a means must be
provided to deliver them back to the front of the line for
reuse.
70

• Pallet fixtures
71

• System Configuration
• In a transfer line, the work flow can take several different
forms, viz.
– (1) In-line, (2) segmented in-line, and (3) rotary.
• The in-line configuration consists of a sequence of stations in
a straight line arrangement.
• This configuration is common for machining big workpieces,
such as automotive engine blocks, engine heads, and
transmission cases since these parts require a large number of
operations (and hence, a large no. of stations).
• The in-line configuration can also be designed with integrated
storage buffers along the flow path.
72

• System Configuration
• The segmented in-line configuration consists of two or more
straight-line transfer sections, where the segments are usually
perpendicular to each other.
• Reasons for designing a production line in these configurations
rather than in a pure straight line
– available floor space may limit the length of the line
– workpiece in a segmented in-line configuration can be reoriented to
present different surfaces for machining
– the rectangular layout provides for swift return of work-holding fixtures
to the front of the line for reuse.
73

• Segmented In-line configurations
L-shaped
U-shaped
Rectangular
74

• Rotary configuration
• The work parts are attached to
fixtures around the periphery of
a circular worktable, and the
table is indexed (rotated in fixed
angular amounts) to present the
parts to workstations for
processing.
• Rotary indexing systems are
commonly limited to smaller
work parts and fewer
workstations, and they cannot
readily accommodate buffer
storage capacity.
• Rotary system usually involves a
less expensive piece of
equipment and typically requires
less floor space.
75

• Types of work part transport mechanisms
• Linear transport systems for in-line and segmented in-line systems
• Linear transport systems include powered roller conveyors, belt
conveyors, chain driven conveyors, and cart-on-track conveyors.
• A chain or flexible steel belt is used to transport parts using work
carriers attached to the conveyor.
• The chain is driven by pulleys in either an “over-and-under”
configuration, in which the pulleys turn about a horizontal axis, or an
“around-the-corner” configuration, in which the pulleys rotate about a
vertical axis.
77

• Types of work part
transport mechanisms
• Linear transport systems
• The belt conveyor can also be
adapted for asynchronous
movement of work units between
stations. The forward motion of
the parts is stopped at each
station using pop-up pins or other
stopping mechanisms.
• Cart-on-track conveyors also
provide asynchronous parts
movement and are designed to
position their carts within about 
0.12 mm, which is adequate for
many processing situations.
78

79
Pallet Conveyer – Chain Drive

• Types of work part transport mechanisms
• Linear transport systems – Walking-beam transfer
• Parts are synchronously lifted up from their respective stations by a
transfer beam and moved one position ahead, to the next station.
• The transfer beam lowers the parts into nests that position them for
processing at their stations. The beam then retracts to make ready
for the next transfer cycle.
80

Work parts at station
positions on fixed
station beam
Transfer beam is
raised to lift work
parts from nests
Elevated transfer beam
moves parts to next
station positions
Transfer beam lowers to drop
work parts into nests at new
station positions. Transfer
beam then retracts to original
position 81

• Types of work part
transport mechanisms
• Rotary indexing mechanisms
for dial-indexing machines.
• Geneva mechanism uses a
continuously rotating driver to
index the table through a partial
rotation.
• If the driven member has six
slots for a six-station dial-
indexing table, each turn of the
driver results in a (1/6)th rotation
of the worktable, or 60°.
• Geneva mechanisms usually
have four, five, six, or eight slots
- the maximum number of
workstation positions.
82

83
The operation of a four-slot Geneva mechanism

• Geneva mechanism – some equations
Where,  = angle of rotation of worktable during indexing
(degrees of rotation), and ns = number of equally spaced slots in
the Geneva
The angle of driver rotation during indexing = 2, and the angle of driver rotation
during which the worktable experiences dwell time is (360 - 2).
Where, Tc = cycle time, min; and N = rotational speed of
driver, rev/min.
Where, Ts = available service or processing time or dwell
time, min.
Where, Tr = indexing time (or repositioning time), min.
84

• Simple problems on Geneva mechanism
• (1) A rotary worktable is driven by a Geneva mechanism with six slots.
The driver rotates at 30 rev/min. Determine the cycle time, available
processing time, and the lost time in each cycle to index the table.
• Solution
• N = rotational speed of driver = 30 rev/min. ns = number of equally
spaced slots in the Geneva wheel = 6
• The total cycle time is given by, Tc = 1/30 = 0.0333 min = 2.0 sec
• The angle of rotation of the worktable during indexing for a six-slotted
Geneva is given by
 = 360/6 = 60
• The available service time and indexing time are given by
85

• (2) A rotary worktable is driven by a Geneva mechanism with five slots.
The driver rotates at 48 rev/min. Determine (a) the cycle time, (b)
available process time, and (c) indexing time each cycle.
• Solution
• N = rotational speed of driver = 48 rev/min.; ns = number of equally
spaced slots in the Geneva wheel = 5
• The total cycle time is given by, Tc = 1/48 = 0.020833 min = 1.25 sec
• The angle of rotation of the worktable during indexing for a six-slotted
Geneva is given by
 = 360/5 = 72
• The available service time and indexing time are given by
)48(360
72180
= 0.01458333 min = 0.875 secTs =
)48(360
72180 
= 0.00625 min = 0.375 secTr =
86

• (3) A Geneva with six slots is used to operate the worktable of a dial-
indexing machine. The slowest workstation on the dial-indexing
machine has an operation time of 2.5 sec, so the table must be in a
dwell position for this length of time. (a) At what rotational speed must
the driven member of the Geneva mechanism be turned to provide this
dwell time? (b) What is the indexing time each cycle?
• Solution: Given
N360
60360
N
667.0
)2667.0(360
60180
 = 360/6 = 60 Ts = = = 2.5 sec (given)
Hence, N = (0.667/2.5) = 0.2667 rev/sec = 16 rev/min
= 1.25 secAnd, indexing time, Tr =
87

• Storage Buffers
• A storage buffer is a location in a production line where
parts can be collected and temporarily stored before
proceeding to subsequent (downstream) workstations.
• A storage buffer in an automated production line is used
– to reduce the effect of station breakdowns,
– to provide a bank of parts to supply the line,
– to provide a place to put the output of the line,
– to allow for curing time or other required delay associated with
processing, and
– to smooth cycle time variations.
88

• Control of production line
• Controlling an automated production line implies controlling a number
of sequential and simultaneous activities.
• Three basic control functions are important in the operation of an
automated production line: (1) sequence control, (2) safety monitoring,
and (3) quality control.
• Sequence control coordinates the sequence of actions of the transport
system and associated workstations.
• Sequence control function includes both logic control and sequence
control.
• Safety monitoring function ensures that the production line does not
operate in an unsafe manner.
• Safety applies to both the human workers in the area and the
equipment itself.
89

• Control of production line
• Quality control function: Certain quality attributes of the work parts
are monitored.
• The purpose is to detect and possibly reject defective work units
produced on the line.
• The inspection devices required to accomplish quality control are
sometimes incorporated into existing processing stations. In other
cases, separate inspection stations are included in the line for the sole
purpose of checking the desired quality characteristic.
• Programmable logic controllers (PLCs) are the conventional
controllers used on automated production lines today.
• Personal computers (PCs) equipped with control software and
designed for the factory environment are also widely used.
90

• Analysis of Transfer lines
• Three problem areas in the analysis and design of
automated production lines are:
• Line balancing
• Processing technology
• System reliability
• Line balancing
• The total work content to be accomplished on the
automated line must be divided as evenly as possible
among the workstations.
91

• Process Technology
• Refers to the body of knowledge about the particular
manufacturing processes used on the production line.
• In machining process (for e.g.,) process technology includes
aspects such as machinability of the work material, the proper
application of cutting tools, selection of speeds and feeds, chip
control, etc.
• By applying process technology for every process, each
individual workstation in the production line can be designed to
operate at or near its maximum performance.
• System Reliability
• Failure free operation of workstations.
• Automated production lines are integrated and highly complex
and hence, the failure of any one component can stop the
entire system.
92

• Cycle Time Analysis (of transfer lines)
• Cycle time is the processing time for the slowest station on the line
plus the transfer time. It is given by
Tc = Max {Tsi} + Tr where,
• Tc = ideal cycle time on the line, min; Tsi = the processing time at
station i, min; and Tr = repositioning time, called the transfer time, min.
• The Max {Tsi} is the longest service time that establishes the pace of
the production line.
• Due to random breakdowns and planned stoppages in the line,
downtime occurrences cause the actual average production cycle time
of the line to be longer than the ideal cycle time.
• The actual average production time Tp can then be formulated as:
Tp = Tc + FTd
• where F = nxp = downtime frequency, line stops/cycle; and Td =
average downtime per line stop, min.; n = no. of workstations; p =
frequency of station breakdown per cycle at any station i.
93

• Performance Measures (of transfer lines)
Production Rate,
Where, Rp = actual average production
rate, pc/min; and Tp is the actual average
production time.
Where, Rc = ideal production rate, pc/min.
Line Efficiency,
Where, E = the proportion of
uptime on the production line
Where, D = proportion of
downtime on the line
Cost per unit produced, Cpc = Cm + CoTp + Ct
where Cpc = cost per piece, Rs/pc; Cm = cost of starting material, Rs/pc; Co =
cost per minute to operate the line, Rs/min; Tp = average production time per
piece, min/pc; and Ct = cost of tooling per piece, Rs/pc.
Co includes the allocation of the capital cost of the equipment over its expected
service life, labor to operate the line, applicable overheads, maintenance and
other relevant costs, all reduced to a cost per minute.
94

• Problems on analysis of transfer lines
• (1) A ten-station transfer line (machine) has an ideal cycle time
of 30 sec. The frequency of line stops is 0.075 stops per cycle.
When a line stop occurs, the average downtime is 4.0 min.
Determine (a) average production rate in pc/hr, (b) line
efficiency, and (c) proportion downtime.
• Solution:
• (a) Tp = Tc + FTd = 0.5 + 0.075(4) = 0.5 + 0.3 = 0.8 min
• Rp = 1/0.8 = 1.25 pc/min = 75 pc/hr
• (b) E = 0.5/0.8 = 0.625 = 62.5%
• (c) D = 0.3/0.8 = 0.375 = 37.5%
95

• (2) In the operation of a 15-station transfer line, the ideal cycle
time = 0.58 min. Breakdowns occur at a rate of once every 20
cycles, and the average downtime per breakdown is 9.2 min.
The transfer line is located in a plant that works an 8-hr day, 5
days per week. Determine (a) line efficiency, and (b) how many
parts will the transfer line produce in a week?
• Solution:
• (a) Tp = 0.58 + 9.2/20 = 0.58 + 0.46 = 1.04 min
• E = 0.58/1.04 = 0.5577 = 55.77%
• (b) Rp = 60/1.04 = 57.69 pc/hr
• Weekly production = 40(57.69) = 2307.7 pc/wk.
96

• (3) A ten-station rotary indexing machine performs nine machining
operations at nine workstations, and the tenth station is used for
loading and unloading parts. The longest process time on the line is
1.30 min and the loading/unloading operation can be accomplished in
less time than this. It takes 9.0 sec to index the machine between
workstations. Stations break down with a frequency of 0.007, which is
considered equal for all ten stations. When these stops occur, it takes
an average of 10.0 min to diagnose the problem and make repairs.
Determine (a) line efficiency and (b) average actual production rate.
• Solution:
• (a) F = np = 10(0.007) = 0.07
• Tc = 1.30 + 0.15 = 1.45 min
• Tp = 1.45 + 0.07(10) = 1.45 + 0.7 = 2.15 min/pc
• E = 1.45/2.15 = 0.674 = 67.4%
• (b) Rp = 1/2.15 = 0.465 pc/min = 27.9 pc/hr
97

• (4) A 22-station in-line transfer machine has an ideal cycle time of 0.35
min. Station breakdowns occur with a probability of 0.01. Assume that
station breakdowns are the only reason for line stops. Average
downtime = 8.0 min per line stop. Determine (a) ideal production rate,
(b) frequency of line stops, (c) average actual production rate, (d) line
efficiency, (e) what probability of breakdowns do you expect for a line
efficiency of 72%?
• Solution:
• (a) Rc = = 2.857 pc/min = 171.4 pc/hr
• (b) F = np = 22(0.01) = 0.22
• (c) Tp = 0.35 + 0.22(8) = 0.35 + 1.76 = 2.11 min
• Rp = = 0.4739 pc/min = 28.44 pc/hr
• (d) E = = 0.1659 = 16.59%
• (e) p = 7.27 x 10-4
98

• (5) A transfer machine (production line) has six stations that function
as follows:
99
Station Operation Process time Probability or frequency of a
failure at station i, pi
1 Load part 0.78 min 0
2 Drill three holes 1.25 min 0.02
3 Ream two holes 0.90 min 0.01
4 Tap two holes 0.85 min 0.04
5 Mill flats 1.32 min 0.01
6 Unload parts 0.45 min 0
In addition, transfer time = 0.18 min. Average downtime per
occurrence = 8.0 min. A total of 20,000 parts must be processed
through the transfer machine. Determine (a) proportion downtime,
(b) average actual production rate, and (c) how many hours of
operation are required to produce the 20,000 parts.

• Solution:
• (a) Tc = Processing time for the slowest station + Transfer
time = 1.32 + 0.18 = 1.50 min
• F = downtime frequency = 0.02 + 0.01 + 0.04 + 0.01 = 0.08
• Tp = Actual ave. prodn. time = 1.50 + 0.08 (8.0) = 1.50 +
0.64 = 2.14 min
• Proportion downtime, D = 0.64/2.14 = 0.299 = 29.9%
• (b) Rp = 1/2.14 = 0.467 pc/min = 28.04 pc/hr
• (c) H = 20,000 (2.14/60) = 713.3 hr
100

• (6) An eight-station rotary indexing machine performs the machining
operations shown in the accompanying table, together with processing
times and breakdown frequencies for each station. The transfer time
for the machine is 0.15 min per cycle. A study of the system was
undertaken, during which time 2000 parts were completed. It was
determined in this study that when breakdowns occur, it takes an
average of 7.0 min to make repairs and get the system operating
again. For the study period, determine (a) average actual production
rate, (b) line uptime efficiency, and (c) how many hours were required
to produce the 2000 parts.
101
Station Process Process time Breakdowns
1 Load part 0.50 min 0
2 Mill top 0.85 min 22
3 Mill sides 1.10 min 31
4 Drill two holes 0.60 min 47
5 Ream two holes 0.43 min 8
6 Drill six holes 0.92 min 58
7 Tap six holes 0.75 min 84
8 Unload part 0.40 min 0

• Solution:
• (a) Tc = Processing time for the slowest station + Transfer
time = 1.10 + 0.15 = 1.25 min/cycle,
• Number of breakdowns = 0 + 22 + 31 + 47 + 8 + 58 + 84 +
0 = 250
• F = downtime frequency = 250/2000 = 0.125
• Tp = Actual ave. prodn. time = 1.25 + 0.125(7.0) = 2.125
min/pc
• Rp = 60/2.125 = 28.2353 pc/hr
• (b) E = 1.25/2.125 = 0.588 = 58.8%
• (c) Total time = 2000(1.25) + 250(7) = 4250 min = 70.83 hr
102

• (7) A 14-station transfer line has been logged for 2400 min to identify
type of downtime occurrence, how many occurrences, and time lost.
The results are presented in the table below. The ideal cycle time for
the line is 0.50 min, including transfer time between stations.
Determine (a) how many parts were produced during the 2400 min, (b)
line uptime efficiency, (c) average actual production rate per hour, and
(d) frequency p associated with transfer system failures.
103
Type of occurrence Number Time lost
Tool changes and failures 70 400 min
Station failures: (mechanical and
electrical)
45 300 min
Transfer system failures 25 150 min

• Solution:
• Total downtime = 400 + 300 + 150 = 850 min
• Number of downtime occurrences = 70 + 45 + 25 = 140
occurrences
• (a) Total uptime = 2400 - 850 = 1550 min
• Number of parts = (1550 min)/(0.50 min/pc) = 3100 pc
• (b) E = 1550/2400 = 0.646 = 64.6%
• (c) Rp = (3100 pc/2400 min)(60) = 77.5 pc/hr
• (d) Transfer system failures: p = 25/3100 = 0.008065
104

• (8) A transfer machine has a mean time between failures (MTBF) = 50
minutes and a mean time to repair (MTTR) = 9 minutes. If the ideal
cycle rate = 1/min (when the machine is running), what is the average
hourly production rate?
• Solution:
• Tc = 1/Rc = 1 min/cycle = 1.0 min/pc.
• Availability A = (MTBF – MTTR) / MTTR = 0.82
• E = A = 0.82 = 82% (assuming the machine works as long
it is available)
• E = Tc/Tp, therefore Tp = Tc/E = 1.0/0.82 = 1.2195 min/pc
• Rp = 1/1.2195 = 0.82 pc/min = 49.2 pc/hr
105

• Automated assembly system
• Refers to mechanized and automated devices that perform
various assembly tasks in an assembly line or cell.
• Designed to perform a fixed sequence of assembly steps on a
specific product.
• Carry out operations to combine multiple components into a
single entity.
• Fall under the category of fixed automation.
• Progress in the automated assembly systems is owed to
developments in the technology (robotics and material handling
equipment).
• Industrial robots have become an integral part.
Automated Assembly Lines
106

• Conditions Suitable for Automated Assembly
• High product demand.
• Stable product design.
• A limited number of components in the assembly.
• Product design factors that allow for automated assembly.
• Automated assembly systems involve a significant
capital expense.
107

• Subsystems (components) of an Automated
Assembly System
• One or more workstations at which the assembly steps are
accomplished.
• Parts feeding devices that deliver the individual
components to the workstation(s).
• A work handling system for the assembled entity.
• (The work handling system moves the base part into and
out of the station).
108

• Types of Automated Assembly Systems
(based on physical configuration)
• In-line assembly machine
• Dial-type assembly machine
• Carousel assembly system
• Single-station assembly machine
109

• In-line assembly machine
• A series of automatic workstations are located along an in-line
transfer system.
• It is the assembly version of the machining transfer line.
• Synchronous and asynchronous transfer systems are the
common means of transporting base parts from station to station
with the in-line configuration.
110

• Dial-type assembly
machine
• Base parts are loaded onto fixtures
or nests attached to the circular
dial.
• Components are added and/or
joined to the base part at the
various workstations located
around the periphery of the dial.
• The dial indexing machine operates
with a synchronous or intermittent
motion, in which the cycle consists
of the service time plus indexing
time.
111
Asby Aut – Automated Assembly Station

• Carousel assembly system
• Represents a hybrid between the circular work flow of the dial-type
assembly machine and the straight work flow of the in-line system.
• Can be operated with continuous, synchronous, or asynchronous
transfer mechanisms to move the work around the carousel.
• Carousels with asynchronous transfer of work are often used in
partially automated assembly systems
112

• Single-station assembly machine
• Assembly operations are performed on a base part at a single
location.
• The operating cycle involves the placement of the base part at a
stationary position in the workstation, the addition of components to
the base, and finally the removal of the completed assembly from
the station.
• The cycle time is longer in a single-station assembly system
because all of the assembly tasks are performed sequentially
instead of simultaneously.
113

• Typical Products Made by Automated Assembly
114
Typical Assembly Processes Used in Automated Assembly
Systems

• Partial Automation
• A combination of automated and manual workstations.
• Automation is introduced gradually on an existing
manual line (automation migration strategy)
• Certain manual operations are too difficult or too costly
to automate. when the sequence of workstations is
planned for the line, certain stations are designed to be
automated while the others are designed as manual
stations.
• Examples…alignment, adjustment, fine-tuning,
inspection for a variety of defect identification, etc.
115

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