Introduction to computer Integrated Manufacturing (CIM)

4/3/2014 1Hareesha N G, Dept of Aero Engg, DSCE, Blore

4/3/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 2

Production System
A collection of people, equipment, and procedures
organized to accomplish the manufacturing
operations of a company
Two categories:
• Facilities – the factory and equipment in the facility
and the way the facility is organized (plant layout)
• Manufacturing support systems – the set of
procedures used by a company to manage
production and to solve technical and logistics
problems in ordering materials, moving work
through the factory, and ensuring that products
meet quality standards

4
Types of Manufacturing Systems
1. Continuous-flow processes. Continuous dedicated production of large
amount of bulk product. Continuous manufacturing is represented by
chemicals, plastics, petroleum, and food industries.
2. Mass production of discrete products. Dedicated production of large
quantities of one product (with perhaps limited model variations).
Examples include automobiles, appliances and engine blocks.
3. Batch production. Production of medium lot sizes of the same product.
The lot may be produced once or repeated periodically. Examples: books,
clothing and certain industrial machinery.
4. Job-shop production. Production of low quantities, often one of a kind, of
specialized products. The products are often customized and
technologically complex. Examples: prototypes, aircraft, machine tools
and other equipment.
4/3/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore

Production
quantity
Continuous-
flow production
Mass
production
Batch
production
Job shop
production
Product variety

Category Automation achievements
Continuous-flow process •Flow process from beginning to end
•Sensors technology available to measure
important process variables
•Use of sophisticated control and optimization
strategies
•Fully computer automated lines
Mass production of discrete products •Automated transfer machines
•Dial indexing machines
•Partially and fully automated assembly lines
•Industrial robots for spot welding, part handling,
machine loading, spray painting, etc.
•Automated material handling systems
•Computer production monitoring
Batch production •Numerical control (NC), direct numerical
control (DNC), computer numerical control
(CNC).
•Adaptive control machining
•Robots for arc welding, parts handling, etc.
•CIM systems.
Job shop production •Numerical control, computer numerical control

The Production System

Production System Facilities
Facilities include the factory, production machines
and tooling, material handling equipment,
inspection equipment, and computer systems
that control the manufacturing operations
• Plant layout – the way the equipment is
physically arranged in the factory
• Manufacturing systems – logical groupings of
equipment and workers in the factory
– Production line
– Stand-alone workstation and worker

Manufacturing Support Systems
Involves a cycle of information-processing
activities that consists of four functions:
1. Business functions - sales and marketing, order
entry, cost accounting, customer billing
2. Product design - research and development,
design engineering, prototype shop
3. Manufacturing planning - process planning,
production planning, MRP, capacity planning
4. Manufacturing control - shop floor control,
inventory control, quality control

Information Processing Cycle in
Manufacturing Support Systems

Automation in Production Systems
Two categories of automation in the
production system:
1. Automation of manufacturing systems in the
factory
2. Computerization of the manufacturing
support systems

Computer Integrated Manufacturing

Mechanization
• Mechanization is providing human operators
with machinery that assist them with the
muscular requirements of work.
• It can also refer to the use of machines to
replace manual labor or animals.
• A step beyond mechanization is automation.
• The use of hand powered tools is not an
example of mechanization.

Automation
• What is automation?
• Why automation is required?
• Which are the operations can be automated in
production system?
• Can automation be implemented suddenly?

Automation
• Automation can be defined as the technology
concerned with the application of complex
mechanical, electronic, and computer-based
systems in the operation and control of
manufacturing systems.

Automation
Automation is the use of control systems
(such as numerical control, programmable logic
control, and other industrial control systems),
in concert with other applications
of information technology
(such as computer-aided technologies [CAD,
CAM,]),
to control industrial machinery and processes,
reducing the need for human intervention.

Automation
• In the scope of industrialization, automation
is a step beyond mechanization.
• Where as mechanization provided human
operators with machinery to assist them
with the muscular requirements of work.
• Automation greatly reduces the need for
human and mental requirements as well.
• Processes and systems can also be
automated.

Automated Manufacturing Systems
Examples:
• Automated machine tools
• Transfer lines
• Automated assembly systems
• Industrial robots that perform processing or
assembly operations
• Automated material handling and storage systems
to integrate manufacturing operations
• Automatic inspection systems for quality control

Automated Manufacturing Systems
Three basic types:
1. Fixed automation
2. Programmable automation
3. Flexible automation

Fixed Automation
A manufacturing system in which the sequence of
processing (or assembly) operations is fixed by the
equipment configuration.
Typical features:
• Suited to high production quantities
• High initial investment for custom-engineered
equipment
• High production rates
• Relatively inflexible in accommodating product
variety

Programmable Automation
A manufacturing system designed with the capability
to change the sequence of operations to
accommodate different product configurations
Typical features:
• High investment in general purpose equipment
• Lower production rates than fixed automation
• Flexibility to deal with variations and changes in
product configuration
• Most suitable for batch production
• Physical setup and part program must be changed
between jobs (batches)

Flexible Automation
An extension of programmable automation in which
the system is capable of changing over from one
job to the next with no lost time between jobs
Typical features:
• High investment for custom-engineered system
• Continuous production of variable mixes of
products
• Medium production rates
• Flexibility to deal with soft product variety

Product Variety and Production
Quantity for Three Automation Types

Reasons for Automating
1. To increase labor productivity
2. To reduce labor cost
3. To mitigate the effects of labor shortages
4. To reduce or remove routine manual and clerical
tasks
5. To improve worker safety
6. To improve product quality
7. To reduce manufacturing lead time
8. To accomplish what cannot be done manually
9. To avoid the high cost of not automating

Production Concepts and
Mathematical Models
• Production rate Rp
• Production capacity PC
• Utilization U
• Availability A
• Manufacturing lead time MLT
• Work-in-progress WIP

Production rate Rp
• Hourly production rate
• Work units completed/Hr
• Cycle time: Time that one work unit spends being
processed or assembled. It is the time between
when one work unit begins processing and next
unit begins.
• Not all time is productive.
• Cycle time consists of i) actual machining
operation time ii) workpart handling time
iii) tool handling time per workpiece

Operation Cycle Time
Typical cycle time for a production operation:
Tc = To + Th + Tth -------------------1
where
Tc = cycle time, min/pc
To = processing time for the operation, min/pc
Th = handling time (e.g., loading and unloading
the production machine), min/pc and
Tth = tool handling time (e.g., time to change
tools), min/pc

Tool handling time
• Time spent changing tools when worn out
• Time required for changing one tool to the
next.
• Tool indexing time for indexable inserts or for
tools on a turret lathe
• Tool positioning for next pass etc..
– These activities do not occur every cycle
– They must be spread over the number of parts

Production rate for
batch production
Time to process one batch(Q units) = Setup time +
processing time, i.e., Tb = Tsu + QTc------------------2
where
Tb = Batch processing time in min
Tsu = Setup time required for one batch in min
Q = Batch quantity, pc
Tc = cycle time per workunit in min/cycle
Tp = Tb / Q ,------------------------3
whereTp= Avg prod. Time/workunit , min/pc
Rp = 60 / Tb ,----------------------4
Where Rp = Hourly prod rate, pc/Hr4/3/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 29

Production rate for
job shop production
Time to process one batch(Q units) = Setup time +
processing time, i.e., Tb = Tsu + QTc
For job shop production, Q = 1
So, Tb = Tsu + Tc = Tp
How??
Tp = Tb / Q , whereTp= Avg prod. Time/workunit , min/pc
Rp = 60 / Tb , Where Rp = Hourly prod rate, pc/Hr

Production rate for
mass production
Production rate = cycle rate of the machine
Tb = Tsu + QTc
For mass production, Q = very large
Tp = Tb/Q = (Tsu + QTc ) / Q = Tsu /Q + QTc/Q
Tp = Tsu/Q +Tc
As Q becomes very large, Tsu/Q  0
So, Tp = Tc
WKT, Production rate is reciprocal of production time
Rp = Rc = 60/Tc

Production rate for
flow line mass production
• Production rate = cycle rate of the production line
• Workstations are interdependent in the line
• Impossible to divide total work equally among all
workstations on the line.
• So, one station ends up with the longest
operation time ( Bottle neck station).
• Bottle neck station sets the pace to other
workstation.
• Work units should be moved from one
workstation to next (Tr )4/3/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 32

Production rate for
flow line mass production
• Cycle time = transfer time + longest processing time
Tc = Tr + Max To -----------------5
• Where Max To = operation time at the bottle neck
station i.e., The maximum of operation times for all
stations on the line
• Tr = Transfer time
Rc = 60/Tc ----------------6

Production capacity
• maximum rate of output that a production
facility (or production line, work center, or group
of work centers) is able to produce under a given
set of assumed operating conditions
• Operating conditions refer to the number of
shifts per day, number of days in the week (or
month) that the plant operates, employment
levels, and so forth.

Production capacity
Let PCw = the production capacity of a given facility under
consideration.
Let the measure of capacity = the number of units produced per
week.
Let n = the number of machines or work centers in the facility.
A work center is a manufacturing system in the plant typically
consisting of one worker and one machine. It might also be one
automated machine with no worker, or multiple workers working
together on a production line.
It is capable of producing at a rate RP unit/hr. Each work center
operates for Hs hr/shift.
Let Sw denote the number of shifts per week.
PCw = n Sw Hs Rp --------------------7

Production capacity
• If we include the possibility that each work
unit is routed through no operations, with
each operation requiring a new setup on
either the same or a different machine,
• where no = number of operations in the routing
o
psw
n
RHnS
PC  ---------8

Production Capacity
Plant capacity for facility in which parts are
made in one operation (no = 1):
PCw = n Sw Hs Rp
where PCw = weekly plant capacity, units/wk
Plant capacity for facility in which parts
require multiple operations (no > 1):
where no = number of operations in the routing
o
psw
n
RHnS
PC 
Hareesha N G, Dept of Aero Engg, DSCE, Blore

Production Capacity
Equation indicates the operating parameters that
affect plant capacity.
Changes that can be made to increase or decrease
plant capacity over the short term are:
1. Change the number of shifts per week (S). For
example, Saturday shifts might be authorized
to temporarily increase capacity.
2. Change the number of hours worked per shift
(H). For example, overtime on each regular
shift might be authorized to increase capacity.
o
psw
n
RHnS
PC 

Over the intermediate or longer term, the following
changes can be made to increase plant capacity:
3. Increase the number of work centers, n, in the shop.
This might be done by using equipment that was
formerly not in use and hiring new workers.
4. Increase the production rate, Rp by making
improvements in methods or process technology.
5. Reduce the number of operations no required per work
unit by using combined operations, simultaneous
operations, or integration of operations.
Production Capacity

Utilization
• Utilization refers to the amount of output of a
production facility relative to its capacity. Expressing
U=Q/PC------------9
Where U = utilization of the facility,
Q = actual quantity produced by the facility during a given
time period (i.e., pc/wk), and
PC = production capacity for the same period (pc/wk).
It is often defined as the proportion of time that the
facility is operating relative to the time available under
the definition of capacity.
Utilization is usually expressed as a percentage.

Availability
• Availability is defined using two other reliability
terms, mean time between failure (MTBF) and
mean time to repair (MTTR).
• The MTBF indicates the average length of time
the piece of equipment runs between
breakdowns.
• The MTTR indicates the average time required to
service the equipment and put it back into
operation when a breakdown occurs.

Availability
Availability is defined as follows:
Availability: A =
where MTBF = mean time between failures, and
MTTR = mean time to repair
Availability is typically expressed as a percentage
MTBF
MTTRMTBF 
-----------10

Availability -
MTBF and MTTR Defined

1) A production machine operates at 2 shifts/day and 5 days a week at full
capacity. Its production rate is 20 unit/hr. During a certain week, the machine
produced 1000 parts and was idle in the remaining time, (a) Determine the
production capacity of the machine, (b) What was the utilization of the machine
during the week under consideration?
if the availability of the machine is 90%, and the utilization of the machines
is 80%. Compute the expected plant output.
Solution:
(a) The capacity of the machine can be determined using the assumed
80-hr week as follows:
PC = 80(20) = 1600 unit/wk
(b) Utilization can be determined as the ratio of the number of parts
made by the machine relative to its capacity.
U = 1000/1600 = 0.625 (62.5%)
(c) U=Q/PC or
Q= UxPCxA or UAxnSHRp

2) The mean time between failures for a certain production machine is 250 hours,
and the mean time to repair is 6 hours. Determine the availability of the
machine.
Availability: A =
3) One million units of a certain product are to be manufactured annually on
dedicated production machines that run 24 hours per day. 5 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, and worker efficiency = 100%, and
that no setup time will be lost, (b) Solve part (a) except that availability = 0.90.
Solution: Tc= 1 min
Tb = Tsu+QTc = 0+QTc
Tp= Tb/Q = Tc
Rp=60/Tp = 60 Parts/Hr
n= PC/SHRp
= 1000000/(50x5x24x60)
= 2.77 = 3 machines
MTBF
MTTRMTBF 

Manufacturing Lead Time
Manufacturing lead time (MLT) is the total time required
to process a given part or product through the plant,
including any lost time due to delays, time spent in
storage, reliability problems, and so on.
 Production consists of a sequence of individual processing and
assembly operations. Between the operations are material
handling, storage, inspections, and other non productive activities.
 Divide these activities as operation and non operation elements.
 Non operation elements are Handling, temporary storage,
inspection and other sources of delay when work unit is not in
machine.

Let Tc = the operation cycle time at a given machine or workstation,
Tno = the nonoperation time associated with the same machine.
no = the number of separate operations through which the work unit
must be routed
Tsu = Setup time required to prepare each production machine for the
particular product. If we assume batch production, then there are
Q work units in the batch.,
Given these terms, we can define manufacturing lead time as
MLTj =
where
MLTj = manufacturing lead time for part or product j (min).
Tsuji = setup time for operation i (min) for the product j,
Qj = quantity of part or product in the batch (pc),
Tcji = operation cycle time for operation i (min/pc),
Tnoji = nonoperation time associated with operation i (min), and
i indicates the operation sequence in the processing; i = I, 2,... noj


ojn
i
nojicjijsuji TTQT
1
)( -----------11

To simplify and generalize the model,
let us assume that all setup times, operation cycle times, and non
operation times are equal for the noj machines.
Further, let us suppose that the batch quantities of all parts or
products processed through the plant are equal and that they are
all processed through the same number of machines, so that noj =
no , With these simplifications, Eq. becomes:
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
-----------12

• For a job shop in which the batch size is one (Q = 1), Eq.
(1.12) becomes
MLT=no(Tsu+TC+Tno)------------ (1.13)
For mass production, the Q term in Eq. (1.12) is very large
and dominates the other terms.
In the case of quantity type mass production in which a
large number of units are made on a single machine (no
=1). The MLT simply becomes the operation cycle time for
the machine after the setup has been completed and
production begins.
MLT = QxTc ------------1.14

For flow line mass production, the entire production line is
set up in advance. Also, the non operation time
between processing steps is simply the transfer time Tr
to move the part or product from one workstation to
the next. The station with the longest operation time
sets the pace for all stations:
MLT =no(Tr +Max To) = noTc --------------1.15
Since , (Tr +Max To) = Tc (1.5)
Since the number of stations is equal to the number of
operations (n = no) Eq. (1.15) can also be stated as
MLT =n(Tr +Max To) = nTc --------------1.16

A certain part is produced in a batch size of 100 units. The batch must be routed
through five operations to complete the processing of the parts. Average
setup time is 3 hr/operation, and average operation time is 6 min . Average
non operation time due to handling, delays, inspections, etc., is 7 hours for
each operation. Determine how many days it will take to complete the batch,
assuming the plant runs one 8-hr shift/day.
Solution:
Given:
Q = 100 units
no = 5
Tsu = 3hr/operation
Tc = 6 min
Tno = 7 hr/operation
The manufacturing lead time is computed from Fq
MLT = no (Tsu + QTc + Tno)
MLT = 5(3 + 100 X 0.1 + 7) = 100 hours
At 8 hr/day. this amounts to L00/8 = 12.5 days.

A certain part is routed through six machines 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.
Solution:
Given:
Q = 100 units
no = 5
Tsu = 3hr/operation
Tno = 12hr/machine
The manufacturing lead time is computed from Fq
MLT = 

ojn
i
nojicjijsuji TTQT
1
)(

A certain part is routed through six machines in a production plant. The
operation times for each machine are given in the table below. Suppose the
part is made in very large quantities on a production line in which an
automated work handling system is used to transfer parts between machines.
Transfer time between stations = 15 s. The total time required to set up the
entire line is 150 hours. Assume that the operation times at the individual
machines remain the same. Determine (a) manufacturing lead time for a part
coming off the line.(b) production rate for operation 3. and (c) theoretical
production rate for the entire production line.
Solution:
Given:
a) MLT = no(Tr+MaxTo)
b) Rp3 = 60/Tp ; But Tp = Tc = To
c) Rp = 60/Tp; But Tp = Tc ; But Tc = Tr+Max To

Work-In-Process
Work-in-process (WIP) is the quantity of parts or
products currently located in the factory that
either are being processed or are between
processing operations.
WIP is inventory that is in the state of being
transformed from raw material to finished
product.

Work-In-Process
An approximate measure of work-in-process can be
obtained from the following, using terms previously
defined:
WIP=
where WIP = work-in-process, pc;
A = availability, U = utilization,
PC = plant capacity, pc/wk;
MLT = manufacturing lead time, hr;
Sw = shifts per week,
Hsh = hours per shift, hr/shift
  
w sh
AU PC MLT
S H

TIP Ratio
The TIP ratio measures the time that the product
spends in the plant relative to its actual
processing time.
It is computed as the total MLT for a part divided by
the sum of individual operation time for the
plant.


oT
MLT
TIP

The average part produced in a certain batch manufacturing plant must be processed
sequentially through six machines on average. Twenty (20) new batches of parts are
launched each week. Average operation time = 6 minutes, 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, and (c) plant utilization,
(d) Determine the average level of work-in-process in the plant.
a) MLT = no( Tsu + QxTc + Tno )
b) PC = A.U. n.SwHs.Rp/no
c) U = Q/PC
d) WIP = A.U.PC.MLT/SwHs

Introduction to computer Integrated Manufacturing (CIM)

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