International Journal of Social Relevance & Concern (IJSRC)
Voulume1 Issue1, December 2013
Production and
Industrial Systems Engineering
EiT-M
Improving Manufacturing Flow using Lean Production Principles in
Ethiopian Textile and Garment Industries
By: TsegayTesfay, GebremeskelKahsay (PhD)
Department of Industrial Engineering, Ethiopia Institute of Technology-Mekelle,
Mekelle University, Ethiopia
Abstract
In today's competitive world, customers are demanding better quality products with faster and
reliable deliveries. To assure this demand, new manufacturing technologies are developing rapidly;
resulting in new products and improvements in the manufacturing process. As part of this effort,
lean production principles have been developed and are in use in developed countries as a key to
remove and minimize wastes. The purpose of this thesis is to adopt lean production in MAA
Garment and Textile Factory so as to reduce work-in-process and production lead time, to
eliminate chance of dirty and delay of production components, to stabilize pace of production
process to pace of customer demand, and to minimize effect of rework and reject on the actual
performance of the process in sewing line.
This research follow qualitative and quantitative research approaches for collecting and analyzing the
data in the case chosen. The main methods used for data collection are shop floor visit, check sheet,
and questionnaire. The empirical findings are analyzed by identifying problems from current state of
production process and by relying on theoretical concepts reviewed in the literature.
The aggregate data collected shows that there are substantial wastes in the production process
and habits of producing products at the day of delivery time by using all available resources, for
example overtime. And the result of the analysis mainly demonstrates that there is inconsistent
production rate per shift, high work-in-process, high production lead time, and process
improvement can be accomplished by applying lean production tools and techniques
Keyword: Lean production, Takt time, Workload balancing, Kanban card, Work-in-Process
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International Journal of Social Relevance & Concern (IJSRC)
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1. Introduction
Textile and garment is one of the oldest industries in the world and has come a long way from
the days when manufacturing was undertaken in consumption centers of US, Europe and Japan
[1]. In 2005, USA and EU set limits in 2005. But china's exports were not affected by this limits
instead its shipment of textiles and clothing even rose 25% in US$ terms in 2006, compared with
a 21% increase in the prior year. This was mainly due to a strong development of sales to other
destinations than the United States and the European Union.
This indicates that, eventually Textile and Garment sector is shifting to newly industrializing
Asian and African countries, majorly on account of relatively low labor cost and abundant raw
material. On account of this, Ethiopia started the modern textile sector in 1939, established by
foreign capital under the name of Dire Dawa Textile Mills [2]. A recent study of the Ministry of
Agriculture indicates that there is 2.6 million hectares of land suitable for cotton production,
which is equivalent to that of Pakistan, the fourth largest producer of cotton in the world. This
sub-sector is the third largest manufacturing industry, which is exporting products to USA
(AGOA), Europe, and other corners of the world; only after food processing and beverage
industry and leather industry. As a result of Ethiopian governmental export incentives and
opportunity of international trading environment in the past few years, the export of textile and
garment product has shown significant increase. With a total output value of 699.91 million Birr,
the contribution of the textile sub-sector to national GDP was about 1% and to the output value
of the manufacturing industry was about 8.31%. Ethiopia is endowed with favorable
geographical and weather conditions and abundant water resources to grow cotton. The
expansion of cotton planting and rise-of yield will guarantee a sufficient supply of raw material
for textile and this condition leads Ethiopia to widely invest on textile and garment sub-sector.
With these evolutionary approaches and fast growing need of human beings for fashion clothing,
textile and garment industries , as part of manufacturing industries, have been invented different
frameworks and methods to create an astonishing array of styles and a considerable effort were
undertaken to develop tools and techniques to use and harmonize these frameworks and methods.
As part of this effort, lean production has been developed and is in use in developed countries as
a key principle to abolish or reduce wastes and on maximizing or fully utilizing activities that
add value from the customer’s perspective in any manufacturing industries. In contrast to this,
Ethiopian textile and garment industry’s customers are getting dissatisfied for many wastes that
can easily minimized and eliminated by lean production principles.
The purpose of this study is to pre-study the current production process of MAA garment and
make a visual representation to analyze them and subsequently exploring and proposing possible
solutions in the production process in order to substantially create smooth working environment
and to improve plant’s ability to produce exactly the right quantity with the right quality at
exactly right time.
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International Journal of Social Relevance & Concern (IJSRC)
Voulume1 Issue1, December 2013
Specifically, it addresses the following objectives
 Create smooth flow of materials, products, and information that are used by operators and
supervisors in their working environment
 Minimizing chance of rework, reject, and dirty and getting qualified process output per
each workstation
 Resolve un-stabilized pace of production process to pace of customer demand at normal
working condition
 Ascertain consistent, timely, and repeatable production process
 Recommend lean production technology
Moreover, this study is heavily designed to play a role in adoption of lean production principles
in Ethiopian Garment and Textile Industries so as to increase the competitiveness throughout the
world by reducing or eliminating wastes observed within the current production process.
This article has five sections. Introduction is the first section and introduces the background
information of topic, defines objective, and finally illustrates the significance of the study. The
second section outlines the concept of lean production principles. It provides comprehensive
angles to analyze and evaluate the study. The third section demonstrates the chosen research
methodologies and a description of how the study is carried out. In section four a general
description of the production process is presented based on shop floor visits, check sheets, and
questionnaires. Process flow chart, tables, and bar charts assist to clarify the description and are
depicted in text and in summarized way. Analysis is one of the main outcomes of this study and
proceeds in this section. It starts with analyzing current state production process and thereafter, it
goes to proposing lean solutions. The article ends with a short conclusion in section five.
2. The concept of Lean production
Reviewing the concept of lean production helps to analyze and evaluate the problems
investigated. It is sourced mainly from books, journals, conference manuals, etc.
After World War I, Henry Ford and General Motors’ Alfred Sloan moved world manufacturing
from centuries of craft production-led by European firms-into the age of mass production-which
led largely United States of America to dominate the global Economy [3]. After world war-II,
Japanese manufacturers were faced with the dilemma of vast shortages of materials and human
resources. These conditions result in the birth of “lean production” business model. In order to
make a move toward improvement, early Japanese leader Shigeo Shingo devised a new,
disciplined, process oriented business model, which is the “Toyota Production System” [4]. This
system was developed and refined between 1945 and 1970, and still growing today all over the
world.
Lean is: Elimination of waste-Toyota Production System, Philosophy-produce only what is
needed, when it is needed, with no waste, Methodology-determination of value added in the
process, and tools like takt time, workload balancing, kanban sizing, standardizing work etc
© 2013, IOURNALS All Rights Reserved
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International Journal of Social Relevance & Concern (IJSRC)
Voulume1 Issue1, December 2013
(table 2.2) [5]. Therefore, Lean production is Japanese production philosophy that focuses on
abolishing or reducing wastes and on maximizing or fully utilizing activities that add value from
the customer’s perspective [6]. In addition, Lean production is a variation on the theme of
efficiency based on optimizing flow; it is a present-day instance of the recurring theme in human
history toward increasing efficiency, decreasing waste, and using empirical methods to decide
what matters, rather than uncritically accepting pre-existing ideas [7]. Lean production combines
the advantages of craft and mass production, while avoiding the high cost of the former and the
rigidity of the later. In Toyota Production System, seven types of wastes were identified by
Shigeo Shingo and Table-2.1 below shows these seven types of wastes and their descriptions.
Table-2.1 type and description of wastes (source: Fawaz, 2003)
S/n
Waste
Description
Producing too much or too soon, resulting in poor flow of
1 Overproduction
information or goods and excess inventory
Frequent errors, product quality problems, or poor delivery
2 Defects
performance
Unnecessary
Excessive storage and delay of information or products, resulting in
3
inventory
excessive, often when a simpler approach may be more effective
Inappropriate
Going about work process using the wrong set of tools, procedures
4
processing
or systems, often when a simpler approach may be more effective
Excessive
Excessive movement of people, information or goods, resulting in
5
transportation
wasted time, effort and cost
Long periods of inactivity for people, information or goods resulting
6 Waiting
in poor flow and long lead times
Unnecessary
Poor workplace organization, resulting in poor ergonomics, for
7
motion
example excessive bending or stretching and frequently lost items
Lean production business model distils the essence of lean approach into five key principles and
shows how the concepts can be extended beyond automotive production to any company or
organization, in any sector.
 Specify what does and does not create value from the customer’s perspective and not
from the perspective of individual firms, functions and departments
 Identify all the steps necessary to design, order and produce the product across the
whole value stream to highlight non value adding waste
 Make those actions that create value flow without interruption, backflows, waiting or
scrap
 Only make what is pulled by the customer.
 Strive for perfection by continually removing successive layers of waste as they are
uncovered
2.1 Lean production elements
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International Journal of Social Relevance & Concern (IJSRC)
Voulume1 Issue1, December 2013
Lean production is a holistic view; it emphasizes the interconnectivity and dependence among a
set of five key/primary elements. These five primary elements are: Manufacturing Flow,
Organization, Process Control, Metrics, and Logistics (Table 2.2).
Table 2.2 five primary elements of lean production (source: William, 2001)
Manufacturing flow Process control
Organization
Logistics
Metrics
 Product/quantity
 Total productive
 Product Forward plan
 On-time
assessment
maintenance
focused,
delivery
(product group)
multidiscipline
team
 Process mapping  Poka-yoke
 Lean
 Mix-model
 Process
management
manufacturing
lead-time
development
 Routing analysis
 Graphical work
 Training (lean
 Level loading
 Total cost
(process, work,
instructions
awareness, cell
content, volume)
control, metrics,
SPC)
 Takt calculations  Visual control
 Communication  Workable
 Quality
plan
work
yield
 Workload
 Continuous
 Roles and
 Kanban pull
 Inventory
balancing
improvement
responsibility
signal
 Kanban sizing
 Statistical Process
 ABC parts
 Space
Control (SPC)
handling
utilization
 Cell layout
 5S (housekeeping)
 Service cell
 Travel
agreements
distance
 Standard work
 Customer/
 Productivity
supplier
alignment
 One-piece flow
 Operational
rules
3. Methodology
This study ismade by acquiring all input resources to achieve the objectives defined in the earlier
section. A qualitative and quantitative analysis is used in which the main emphasis of the
qualitative method is to gain insight of the plant’s current production process by using
questionnaires and informal interviews and the quantitative method is used to gain the insight of
the current production process using shop floor visit & check sheets, and toconstructexplanations
and techniques to create improved production process by integrating manufacturing lead time,
© 2013, IOURNALS All Rights Reserved
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International Journal of Social Relevance & Concern (IJSRC)
Voulume1 Issue1, December 2013
work-in-process, resource utilization, and quality level per output of subsequent process as
performance measuring parameters.
3.1 Data collection
Two types of data are used to conduct the research: primary and secondary data. Primary data are
collected physically from the production plant and the secondary data are collected based on data
collected by other sources.
A) Primary data collecting methods:
 Shop floor visit and intensive physical observation is made
 Check sheet is used to record production lead time, produced versus defective
products, and the bottlenecks occurred
 Questionnaires are developed and distributed, and then compiled
 Informal interviewees are conducted with concerned bodies
B) Secondary data collecting methods:
 Relevant literatures are reviewed to help achieve the defined objectives
 Manuals, historical documents, and other necessary sources are used
The shop floor visit:Shop floor visit was the best way to show how the current production
process is running. Direct observation of all jobs in the production plant with sufficient
measurements to present a reliable picture of the work performed, may take a tremendous
amount of time. Thus, work sampling is used to obtain all necessary data through shop floor
visit. Work sampling is the process of making sufficient random observations of an operator’s
activities to determine the relative amount of time the operator spends on the various activities
associated with the job [18]. The production plant has 16 sewing lines and 10 of them were
producing one order, KK (German order); and on average 7 of the 10 lines are assigned to
produce round neck t-shirt. Based on this classification, the sample line selected for shop floor
visit is line-3 and its materials preparation and the current order selected is round neck t/shirt
with order quantity of 327,360 pieces. This line is selected based on the operator’s efficiency in
which it is the most effective line and this is enriched by physical observation of researcher and
supervisor. Shop floor visit was supported with informal interview when something is not
clarified by observation.
Two techniques are used to record the shop floor visit:
 Process flow chart: which clarifies the sequence in which activity elements take place and
 Check sheet: which records three things: production lead time, produced versus defective
products, and the bottlenecks occurred
The actual time of operation is measured by an observer (the researcher) with stopwatch. And the
minimum number of observations made for 5% accuracy and 95% confidence level is
calculated with the relation shown below [19]:
40√𝑛(𝑓𝑥 2 )−[(𝑓𝑥)]2 2
]
(𝑓𝑥)
N=[
Where; n = f = number of observations taken initially
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International Journal of Social Relevance & Concern (IJSRC)
Voulume1 Issue1, December 2013
f = frequency of observation
x = value of observations
N = number of observations required for 95% confidence level and 5% accuracy
Based on the above relation, the number of readings (cycles) made for each job of the work-inprocess is 14. That is, to calculate the production lead time of one product, the researcher made
14 readings and come up to average production time and the result is shown in table 4.2.
Moreover, the above equation is used to calculate the number of readings for produced quantities
versus defective quantities.
The questionnaires:Questionnaires are developed and distributed to get a supportive ideas and
are obtained from operators and supervisors since those employees are routine workers in the
specified production plant. As explained in shop floor visit, it may take tremendous amount of
time to make direct observation of all jobs and to distribute questionnaires to all employees to
present a reliable picture of the work performed. Therefore, the researcher used sample size of 45
employees which are workers from line-3 (100% of them) and workers from cutting and
finishing sections (15% of them).
The informal interview:It is mainly made by a face-to-face meeting, but sometimes it is preceded
by telephone, in which a researcher asked an individual a series of questions and gets the
necessary data. The researcher is the main interviewee and production managers are the repliers.
It supports shop floor visit and questionnaire.
3.2 Data analysis
After deciding to use line-3 and round neck t/shirt order for data collection (section 3.1), the
intensively collected data are came to in-depth analysis relating with the objectives defined using
the concept of lean production reviewed in section two to improve the productivity of the plant.
Diagrammatically the procedural analyzing steps are shown as in figure 3.1 below.
What to do?
Achieve the
defined
objectives
What tools and
techniques to use?
 Process flow
chart
 Takt time
 Workload
balancing
 Kanban card
 5S
Packages and Microsofts
used?
 SPSS to display necessary
frequencies and graphs
data
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 Microsoft Office Excel






How to continue?
Understand the current
flow process of the plant
and get information about
order and its delivery time
Calculate takt time
Balance workload
Use kanban card
Execute 5S tools
Productivity improvement is
relative to
 All resourcesresponsible to
complete the specific
activities/tasks, work-inprogress materials, and
information
What are the
potential measures?
 Manufacturing
lead time
 Work-in-process
 Utilization
 Quality
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International Journal of Social Relevance & Concern (IJSRC)
Voulume1 Issue1, December 2013
Figure-3.1: Diagrammatical illustration of analysis
The allowances:During any prolonged work period (e.g., the typical eight-hour workday) people
do not work continuously [20]. They engage in activities that are not directly task-related, or they
stop working entirely due to various causes. Typical nonworking periods may include such
things as: taking recognized beverage, snack or meal breaks, resting to overcome fatigue,
interruptions to the work cycle, talking to other workers (about either job-related or personal
matters) etc. Therefore, manufacturing industries are obligated to have customary PFD
allowances and as part of this MAA Garment and Textile factory and Juki give the following
customary standards for PFD allowances while producing round neck t/shirt
 Personal and Fatigue allowances = 9% (MAA Garment and Textile factory)
 Unavoidable delay allowance = 14% (Juki standard for single and double needle
machine’s delay, the line uses these machines)
4. Results and Discussion
C/activity
Delay
Inspection
Storage
Moving
Operation
S/N
4.1 Analysis of results
This section initially outlines the current production process of the case as observed by the
researcher and then represents the observed results using process flow chart, tables, and bar
charts. Thereafter, it goes to the core part, analyzing the empirical results and discussing the
various aspects of the subject pertaining to the case.
Process flow chart is used to represent the material flow of the plant or the shop floor visits made
by the researcher. Flow process chart is the most universally recognized and widely used form of
process representation and it captures the sequence in which activity elements take place [20].
The flow process chart starts by bringing fabric from main warehouse and terminates by
transporting the packed product to store for loading. Here in this article, only the activities and
tasks of sewing section are represented using process flow chart, tables, and bar charts. Table 4.1
below shows results of shop floor visit using process flow chart
Table-4.1 Flow process chart of activities and their descriptions
Job Description
1
Checking quantitatively and transporting those bundled
pieces from shelf to sewing line by sewing line feeders
2
Components wait until the first sewing task starts
3
Shoulder attach and immediate transportation to the next
workstation
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International Journal of Social Relevance & Concern (IJSRC)
Voulume1 Issue1, December 2013
4
Shoulder top stitch and simultaneously transported to
next workstation
5
Neck rib tacking and pushing to next workstation
6
Neck rib attach by two similar machines and holding
them until the operators reaches 24 pieces or more to
know his/her target (see figure-4.1a)
Table 4.1: “continued”
7
8
Next workstation becomes idle because of holding in the
previous workstation (see figure-4.1b)
Sleeve attach by two similar machines and
simultaneously transported to next workstation
9
Excess products between two successive workstations
due to low efficiency of an operator in the next
workstation (see figure-4.2a)
10
Sleeve top stitch and immediate transportation to the next
workstation
11
Piping attach and pushing to next workstation
12
13
14
15
16
17
Back piping top stitch and simultaneous transportation to
next workstation
Front piping top stitch and immediate transportation to
the next workstation
Bringing quantitatively checked labels from satellite store
by sewing line feeders
Mountain of products waiting for label (figure-4.2b)
Label attach and immediate transportation to the next
workstation
Side seam by two similar machines and simultaneously
transported to next
18
Bottom and sleeve hemming using two similar machines
19
Trade and fabric trimming
20
Waiting until it is demanded by an offline quality checker
21
Quality checking for sewing defects like skip stitch,
broken stitch, stain etc
22
23
24
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Rejected pieces are placed aside or under the quality
checking table
Defective products moves back for rework
Accepted products wait until they are pushed to ironing
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International Journal of Social Relevance & Concern (IJSRC)
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Pushing checked products to iron machine for ironing
25
Note in table 4.2 above that:
 C/activity is abbreviation for combined activity
 The black colored symbols are the activities identified per each job
 One roll of fabric produces 9 pieces of products
(a)
(b)
Figure 4.1 excessive products and idle workstations
(a) Excess products due to low efficiency of an operator
(b) products waiting for label
Figure 4.2 excess inventory-in-processes
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International Journal of Social Relevance & Concern (IJSRC)
Voulume1 Issue1, December 2013
The other technique used to represent the current production process is “table” which obtained
from check sheet. The target of using check sheet is to determine the production lead time of a
product per given cycle time and to indicate the variation of produced quantities and accepted
products in the process.
The production lead time of each activity to produce one piece of product is illustrated in table
4.2 below. (Note that: the serial number (S/N) described in this table matches exactly the job
description of sewing section in table 4.1).
Table 4.2 average production lead time of each job in sewing section
Average
Average
Average
Average
S/N
processing time inspecting time moving time in waiting time
in minutes
in minutes
minutes
in minutes
0
0.154
0.187
0
1
0
0
0
0.32
2
0.066
0
0.047
0
3
0.12
0
0.07
0
4
0.13
0
0.087
0
5
0.24
0
0
0
6
0
0
0
0.14
7
0.26
0
0.0897
0
8
9
0.093
0
0.039
0
10
0.093
0
0.0292
0
11
0.096
0
0.049
0
12
0.082
0
0.072
0
13
14
0
0
0.0802
0
15
16
17
18
19
20
21
22
23
24
25
0
0.079
0.232
0.495
1.03
0
0
0
0
0
0
0
0
0
0
0.152
0
0
0
0.03
0.0572
0.083
0.087
0
0
0
0.017
0.0802
0
0
0
0.05
0.36
0
0.0203
0
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Remark
One supply
for one shift
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International Journal of Social Relevance & Concern (IJSRC)
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Total
3.016
0.306
1.0242
0.9705
Furthermore, table 4.3 below indicates the rework and rejected quantities relative to total
produced quantities per shift for total of 32 working shifts. In 28th shift of the table, there are no
produced quantities and accepted quantities (zero values). This does not mean that the factory
was closed; instead factory was open and all employees were ready for work but production
stopped for one shift due to shortage of supply. And again the last row shows the average value
of each parameter which helps to calculate the utilization of resources (figure 4.5).
Table 4.3 Produced quantity versus defective products
Shift
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Produced/Checked quantity
855
699
835
844
853
817
810
506
604
461
824
355
236
253
92
126
338
229
52
46
593
825
826
684
825
829
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Accepted quantity
800
671
800
800
802
800
786
483
580
443
790
338
225
244
88
121
330
223
50
42
570
800
800
650
800
800
Rework
40
28
35
37
38
17
20
11
20
18
25
15
4
6
4
4
7
5
2
4
20
19
18
20
18
20
Rejected quantity
15
0
0
7
13
0
4
12
4
0
9
2
7
3
0
1
1
1
0
0
3
6
8
14
7
9
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International Journal of Social Relevance & Concern (IJSRC)
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626
600
19
7
27
0
0
0
0
28
525
510
10
5
29
608
600
4
4
30
659
640
15
4
31
391
370
8
13
32
Sum
17226
16556
511
159
Average
539
518
16
5
As it is justified in section 3.1, the order selected to wind-up the study is KK order (round-neck
t/shirt). Based on this table 4.4 below shows the number of activities within the whole production
plant (cutting, sewing, and finishing/packing sections) in which the second and third columns of
the table shows the frequency and percentage of each activity respectively.
Table 4.4 summary of flow process chart activities
Row No.
Summary of flow process chart
2
Activities
Count Percentage
3
Operation
19
31.67
4
Sub total
19
31.67
5
Moving/transportation
9
15.00
6
Storage
4
6.67
7
Inspection
5
8.33
8
Sub total
18
30
9
Delay
13
21.67
10
Sub total
13
21.67
11
Combined activity
10
16.66
12
Sub total
10
16.66
13
Grand total
60
100.00
The fourth row indicates the total percentage of operating activities which are the value adding
activities from the customer viewpoint, the eighth row designates the total percentage of count of
non-operating and necessary non-value adding activities (moving, storage, and inspection
activities) because do not make a product more valuable but are necessary unless the existing
process is radically changed, and the tenth row explains count of non-operating and non-value
adding activities (delay activities) because these activities are not necessary under present
circumstances. Generally the table explains that the operating activities are 20% smaller than the
non-operating activities excluding combined activities. Here combined activities indicate
simultaneous activities and it is difficult to assign them as either operating or non-operating
activities. This is signaling that there is high waste of resources in non-operating activities which
leads to high inventory-in-process, high manufacturing lead time, and frequent errors.
From table 4.2, the total production lead time to produce one piece of product is summation of
operating/processing time, inspecting time, moving/transporting time, and waiting time. That is,
MLT = ∑𝑛𝑖=1 𝑄(𝑡𝑖 + 𝑎𝑖 ) + 𝑚𝑖 + 𝑞𝑖
Where, MLT is for manufacturing/production lead time to complete one piece of product
Q = work pieces going through a sequence of n operations = 1 piece
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International Journal of Social Relevance & Concern (IJSRC)
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𝑡𝑖 = operating/processing time of 𝑖 𝑡ℎ operation = 3.016 minutes
𝑎𝑖 = inspection time 𝑖 𝑡ℎ operation = 0.306 minutes
𝑚𝑖 = transporting/moving time 𝑖 𝑡ℎ operation = 1.0242 minutes
𝑞𝑖 = waiting time 𝑖 𝑡ℎ operation = 0.9705 minutes
Percentages
Therefore; MLT = 3.016 + 0.306 + 1.0242 + 0.9705 = 5.32 minutes
This time is the current total production time it takes to produce one piece of product at normal
working condition. It is made up of value added time (operating time), the time the customer is
willing to pay for, and non-value added time (non-operating time), times in which either that can
be reduced immediately or that cannot be reduced immediately due to present work rules or
technologies. As it is illustrated in figure 4.3 below, about 43.27% of the time of production is
spent in non-operating time which constitutes 5.75% for inspecting, 19.27% for moving, and
18.25% for waiting times; only 56.73% of its time is spent on the main work or sewing. These
time proportions are evidence of the inefficiencies with which work-in-process is managed in the
process.
60
50
40
30
20
10
0
Percentage of each time
Operating Inspecting Moving
time
time
time
Time in minutes
Waiting
time
Figure 4.3 percentages of production times
To assess the magnitude of these work-in-process problems, TIP ratio is one measure and from
equation below and table 4.3: TIP ratio = 5.32 minutes/3.016 minutes = 2:1
Where, TIP ratio =
MLT
nm To
MLT is total manufacturing lead time for a product = 5.32 minutes = calculated earlier
nm is operations through which a product must routed in order to completely processed
To is operating time of a product per machine or workstation
nm To is average processing/operating time for a product in minutes = 3.016 minutes
This ratio indicates that the total time a product spent in the production is twice larger than the
actual operating time (or) the amount of work-in-process level is twice higher than the work
actually being processed.
One indicator of high work-in-process and production lead time is shown in figure 4.4 below
derived from table 4.3 which demonstrates inconsistent or un-stabilized output per shift. For
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900
800
700
600
500
400
300
200
100
0
Produced quantities
Accepted quantities
Shift-1
Shift-3
Shift-5
Shift-7
Shift-9
Shift-11
Shift-13
Shift-15
Shift-17
Shift-19
Shift-21
Shift-23
Shift-25
Shift-27
Shift-29
Shift-31
Output per shift
example, the output in shift-1 is around 850 pieces and output in shift-21 is below 100 pieces at
same working environment, with similar resource availability, and for one order type. Moreover,
this figure shows two lines (upper and lower lines), one for produced quantities and one for
accepted or good quantities which illustrates that defective products are part of the production
capacity.
Shifts per day
Figure 4.4 production outputs per shift
The percentage of average defective quantities and percentage of utilization relative to the
capacity of the process are illustrated in figure 4.5 below which are obtained from table 4.3.
Part (a) shows percentage of resources utilized which is obtained from
Utilization = Accepted or good quantities/produced quantities
The value of numerator is 518 pieces and value of denominator is 539 pieces
Which yields, utilization =
518
539
= 0.9610 = 96.1% implying that there is 3.9% deviation between
production capacity and producing right products at the right time.
Part (b) and (c) shows percentage of deviations; average defective quantities per shift (2.97% as
rework and 0.93% as reject) which explains significant variations between produced quantities
and accepted or right products.
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Percentages relative to produced quantities
(c) 0.93
(b) 2.97
Accepted quantities
Rework
Rejected quantities
(a) 96.1
Figure 4.5 percentages of utilized resource and defective products
As per the sample size designed in section 3.1, the frequencies and percentage of frequencies for
operator’s and supervisor’s responses are indicated in figure 4.6 (a) to (d) which shows the result
and analysis of questionnaire
Frequency (number
of respondents)
Frequency (number
of respondents)
25
20
15
10
5
0
30
25
20
15
10
5
0
1
1
2
3
4
Importance to Reduce WIP
(a)
2
3
4
Individual's work contribution
to the whole line
(b)
Figure 4.6 questionnaire’s response output
Figure 4.6 (a) shows that about 53% of respondents believe that it is highly important to reduce
Work-in-Process and 29% believe moderately important. Figure 4.6 (b) illustrates that 65% of
respondents say individual’s contribution is high to the whole line, and 33% says it has moderate
contribution. This implies that around 31% of respondents have low satisfaction with their
workstation environment and similarly around 31% are moderately satisfied (figure 4.6 (c)).
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14
12
10
8
6
4
2
0
1
2
3
4
Operators are satisfied with their
workstation environment
Frequency (number of respondents)
Frequency (number of respondents)
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14
12
10
8
6
4
2
0
1
2
3
4
5
Current tools and techniques
used to improve productivity
(c)
(d)
Figure 4.6: “continued”
Furthermore, more than half of respondents believe that standardized work improves
productivity and helps to achieve deliverability at high level and 29% of them believe it
improves moderately. As part of this interest the factory is using its own tools and techniques to
standardize work, to improve productivity, and to achieve deliverability. 44% say current tools
used to achieve deliverability is “over time”, 19% say “working plan” is used, and about 13%
says “target sheet” is used as tools and techniques to improve productivity (figure 4.6 (d)).
4.2 Proposing solutions
The results obtained from process flow chart, check sheet, and questionnaire and the analysis
made in section 4.1 indicates that there are variations and problems of products and resources in
the current production process. The root causes that results-in these variations are: backflow of
materials, loss of accessories (labels and stickers), unpleasant storage of raw materials, scraps,
inefficient resource utilization, inefficiency of manpower, manpower turn over (seek leave,
annual leave, and permanent leave), and absenteeism. Thus, solutions that reduce such variations
should be proposed. This section proposes lean solutions to overcome these problems and to
achieve the objectives defined earlier.
4.2.1 Make takt decision
Calculating takt time took the first effort to propose lean solutions, because it is reflection of
leveling or scheduling customer demand and it is the binding force to use other lean
production/manufacturing tools and techniques. The target of calculating takt time is to produce
a pace not higher than the takt time or to pace production process to rate of customer demand.
One can never measure takt time with a stop watch; he/she must calculate it and is determined
from the following equation:
Takt Time (TT) =
Net available working time per shift in minutes
Customer requirements per shift per one line in pieces
Based on this formula, table 4.5 indicates the calculated takt time. The takt time is calculated in
the last row of the table which explains; the system needs to produce one good unit every 59.2
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seconds to stay in step with the customer’s demand. This is the synchronization time, to
synchronize the external supply. If this is met, the first strategy has been executed successfully.
Table 4.5 Calculating takt time/takt decision
Takt Time Calculation
Description
Time
Total number of days per six months
180
Non-working days (Sunday + Compulsory days)
33
Last shipment’s average period in days
17
Net available working days per six months
130
Working Shift
One shift
Total time available per shift in minutes
540
Lunch time per shift in minutes
60
Personal, Fatigue, and Delay (PFD allowances) in minutes
125
Net available working time per shift in minutes
355
Net available working time per six months in minutes
46150
Total order (round neck t/shirt) in pieces
Customer requirements per shift per seven lines in pieces
Customer requirements per shift per one line in pieces
Takt Time in seconds
Quantity
Remark
e.g. Easter
02:00-11:00 LT
06:00-07:00 LT
23% (section 3.2)
327360
2519
360
Section 3.1
59.2
4.2.2 Balance workload
As it is described in section 4.2.1, once a takt decision has been determined, it is now a matter of
comparing several activities of the process and the takt time and improving all activities and
optimizing all available resources in order to design a balanced workload. Workload balancing,
which is accomplished much more easily in an assembly environment than in a fabrication
environment [7], is done to see how well the actual work elements will fit into the decided takt
time. workload balancing, has to do with examining individual work elements of each operation
and determining if they can be reduced, shifted, re-sequenced, combined, or eliminated. After
each activities are determined for the product (table 4.1), they are compared to the overall takt
time of the system. This information is placed on a loading chart (figure 4.7 below) drawn from
table 4.2 in which the heights of bars indicate the existing cycle time per individual activity. It
compares the takt time (the dotted horizontal line) to current cycle time of each activity.
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Cycle time in minutes
1.4
1.2
1
0.8
0.6
Time
0.4
0.2
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
Stations
Figure 4.7 existing production’s loading chart
This balance chart shows graphically the wastes, which is the distance from the top of the bar
graph for any station to the taktline; if the production could be made at taktrate. Moreover, three
things are observed
 First, by comparing the heights of the bars, it can be seen the degree of unbalanced
workload at a glance which demands rebalancing
 Second, the balance is poor since the difference between the tallest bar and the shortest
bar is extremely high. That is, the tallest bar demands 67 seconds (station-18) and the
shortest bar demands around 1 second (station-22) which implies there is 98.5%
deviation between these two times.
 Third, the highest bars are pointing bottlenecks, because they are followed by high semifinished inventory. The highest bottleneck (the longest cycle time) occurs once, station18 which shows 67 seconds to complete the activity, upper than the takt time.
These points lead the shortest bars to have high work-in-process until the largest bars complete
their task. Thus, cycle time of each bar should be similar to each other and less than takt time but
synchronized to takt. Synchronization is made by redistributing the activities at the workstations.
To make this synchronization recall from table 4.2 and table 4.5 respectively that, the process
needs 5.32 minutes or 319.2 seconds production lead time to complete a product and a takt of
59.2 seconds. But to synchronize these activities to takt, at a minimum requirement all waiting
time should be eliminated [7] and this gives a total time of 260.77 seconds (table 4.6 below)
which is 319.2 seconds less 58.43 seconds for waiting time. This yields: 260.77 seconds of
work/
260.77 seconds of work/5 stations = 52 seconds per station which is the designed cycle time for
the theoretical stations (this designed cycle time is less than the takt time, 59.2 seconds). This
will work as a starting point. Therefore, the balance will be based on five working areas/cells or
stations and a designed cycle time of 52 seconds. Note that: 𝑌1 represents number of current
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staffing requirements or stations and 𝑌2 represents number of new staffing requirements or
working cells/areas
Table 4.6 Balancing workloads
S/N
𝒀𝟏
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
10
10
11
11
Activity description
Checking quantitatively and transporting
those bundled pieces from shelf to sewing
line by sewing line feeders
Shoulder attach and immediate
transportation to the next workstation
Shoulder top stitch and simultaneously
transported to next workstation
Neck rib tacking and pushing to next
workstation
Neck rib attach by two similar machines
Sleeve attach by two similar machines and
simultaneously transported to next
workstation
Sleeve top stitch and immediate
transportation to the next workstation
Piping attach and pushing to next
workstation
Back piping top stitch and simultaneous
transportation to next workstation
Front piping top stitch and immediate
transportation to the next workstation
Bringing quantitatively checked labels
from satellite store by sewing line feeders
Table 4.6: “continued”
Label attach and immediate transportation
12
12
to the next workstation
Side seam by two similar machines and
13
13
simultaneously transported to next
14 14’ Trade and fabric trimming
14 Trade and fabric trimming
15
16 14” Trade and fabric trimming
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Current workload
Time per
station in seconds
Rebalanced workload
Time per
𝒀𝟐
station in seconds
20.46
6.78
51.66
1
50.63
2
51.64
3
53.02
53.82
4
5
11.4
13.02
14.4
20.98
7.92
7.33
8.70
9.24
4.81
6.54
17.35
67.02
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Bottom and sleeve hemming using two
34.68
similar machines
Quality checking for sewing defects like
16
9.12
18
skip stitch, broken stitch, stain etc
Pushing checked products to iron machine
18
1.02
19
for ironing
Total
260.77
260.77
Note in the above table that the sequence of activity number “14” and activity number “15” is
reversed in requirement of balancing the loading chart. Again the table illustrates that the
average time needed to complete “trade and fabric trimming” is 67.02 seconds which is 7.8
seconds above the takt time. But based on the takt decided earlier, any time should not be above
the takt time. Thus, about 5 seconds of “trimming activity” should be performed by any staff
from station-3 and 9 seconds of the “activity” should be performed by any operator from station5 to reduce the delay.
After balancing the workloads and making necessary rearrangements, the loading chart obtained
is shown in figure 4.8 which formulate two dotted horizontal lines and five almost similarly
heighted vertical lines. The upper dotted horizontal line indicates the takt time, calculated earlier
and the lower dotted horizontal line indicates the newly designed cycle time per cell or station,
52 seconds.
17
15
Figure 4.8 Balanced production loading chart
This loading char (figure 4.8) illustrates the following points
 The heights of the bars are almost similar to each other and with the designed cycle time
 The balance is good since the difference between the tallest bar and the shortest bar is
reasonable. That is, the tallest bar is 53.82 seconds (station-5) and the shortest bar is
50.63 seconds (station-2) which means that there is only 5.9% deviation between them
 There is no bottleneck in the process, because the figure justifies that all cycle times of
each working cell or station are below the decided takt time
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Furthermore, by comparing figure 4.7 and 4.8 the following results are obtained
 The balance is reasonable; since all cycle times shown in figure 4.8 are similar and
synchronized to takt; clearly an improvement in balance
 The waste is substantially reduced because in figure 4.7 there was 98.5% difference
between the tallest and shortest bars and in figure 4.8 the difference becomes 5.9% which
shows 92.6% reduction in work-in-process after balancing the workload
 Figure 4.7 shows that the maximum time needed to produce one piece of product is 67.02
seconds, and figure 4.8 designs that the maximum time needed to produce one piece of
product is 53.82 seconds; the difference between these two times to produce one piece of
product is 13.2 seconds
 This value shows that as a result of using the newly decided takt time and balanced
workload: 13.2 seconds * 327360 pieces (total ordered quantity, section 3.3) =
72019.2 net working minutes or around 51 days can be saved
4.2.3 Use kanban card
After the production scheduling process is completed, the generated takt decision is transferred
into production line by the physical Kanban (for example, figure 4.9). Process improvement in
kanban system is accomplished by reducing inventory. To reduce this inventory in the process:
eliminate waiting time and reduce any of the other three times discussed earlier, reduce the
pickup volume by the customer, reduce the variation in the production rate, and reduce the
variation in the customer demand. After making all those reductions and eliminations, follow the
basic rules of kanban system to create smooth flow of materials and products.
Product Name: t/shirt
Part number: ART-5575
Part description: Round neck and short sleeve
Process
Part quantity: __
Point of consumption: fabric=289 gsm, and labels=1
Point
of supply: Warehouse
piece each
Figure 4.9 Physical production kanban card Sewing
In running a kanban process the question of how many kanban to use is a basic issue. If there is
not enough kanban, the system may not be producing quickly enough. The goal is to continually
improve the efficiency of the work-in-process, which means striving to reduce the number of
kanban cards and the amount of inventory in the process. Thus, the number of kanban card is
calculated as [7]:
N=(
Designed production rate per shift∗ production lead time
Available time per shift
)/Size of container
Where: N = total number of kanban or containers (one kanban card per container)
Designed production rate = 360 pieces/shift, table 4.5
Production lead time = designed cycle time = 52 seconds per station, section 4.2.2
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Available time per shift = 355 minutes, table 4.5
Size of container = 4 bundles (it can be variable)
Therefore, number of kanban card = {(360*52)/355}/4 = 14 cards, this is average value
The product has kanban attached. When the customer comes for his/her pickup, the kanban are
removed and placed in a temporary kanban post. From here, the kanban are picked up, normally
by a materials handler, and transported to kanban shelf in front of the production line. From here,
the production workers withdraw the kanban from the shelf in sequential order, and the process
then produces the product in the quantity listed on the kanban. The kanban has just served to be a
production work order to trigger production. The worker again attaches the kanban to the
products made and they are placed in the designated spot, ready for pickup. On this normal
circulation, the materials handler picks up the products with kanban attached and continues the
circulation as shown in figure 4.10 below.
FIFO
FIFO
Raw
material
(accepted
fabric)
shelf
2
5
6
8
FIFO
13’
9
14
Passing table (material flow)
1
3
4
6
7
’
FIFO
10
15
12
13
14
’
11
FIFO
1
1
Label
box
17
16
FIFO
Kanban
shelf
Figure 4.10 Production line layout and flow of kanban card
Representations: the shapes shown in figure 4.10 represents the following terms
Manpower flow
Flow of raw material
Workstations
Kanban card
Flow of kanban card
In figure 4.10, the numbers indicates the sequential layout of machines and resource movements
4.2.4 Implement 5S tool
Most people underestimate the importance of safety, order, and cleanliness in a workplace.
However, Toyota and Honda validates that; “25 to 30% of all quality defects are directly related
to this issue” [7]. As it is explained in section 4.2.2, workload balancing demands eliminating
waiting time and other unnecessary activities. To sustain this, to keep clean the workplace, and to
control a process as a whole, 5S is one of the key lean production tool. Therefore, after the
workload activities are fit into the designed takt, everything has a place and it should be located
in its place. To realize this workplace organization, follow the subsequent actions as a
supplementary requirement to control the process in addition to tact decision, workload
balancing, and using kanban cards:
1. Identify and arrange all items in its area (no loose of resources)
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This is the first step. Assign workers who work in the area and order them to remove everything
from the area that is not required in order to do the work in that area. The identification tool here
is the ‘‘red tag’’ [14] (figure 4.11 (a) below). Designate a red-tag area and rope it off. Complete
the information and attach a red tag to all items that are not needed to meet production
requirements in that area. Remove those items to the red-tag or discharge area (figure 4.11 (b)).
(a) (source: Bill, 2005)
(b)
Figure 11 Red Tag format and red tagged raw material and discharge area
2. Label locations for raw materials and equipments
Once sorting is completed (all non value-added items are identified and moved), the next step is
to organize the items that are needed in the best way possible.
(a) During 5S (shelf is cleared)
(b) after 5S (arranging parts and adding value)
Figure 4.12 during and after 5S
3. Clean up per a unit time
After fabrics, accessories, and other fixtures are placed in their proper position, the next step is
clean up the workplace per unit time (for example, daily or weekly); which is the third element
of 5S. It has to do with cleaning the working environment so as to sustain an improvement.
4. Be able to visually identify any abnormalities
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In order to maintain the improvement it should be done on a consistent basis, otherwise
everything will be back to what it was before. How this is done? A team of people should be
assigned to conduct a timely audit whether every 5S tools are being pursued; because it is hard to
obtain results right away at the start up of a new tool and technique. Then develop a checklist or
assessment sheet to follow up these tools (see table 4.7 below).
Table 4.7 5S checklist audit format (source: Bill, 2005)
Date:______________ Target area:______________ Performed by:____________________
Score
5S elements
Descriptions
Remark
1 2 3 4 5
Necessary items are sorted from those that are unnecessary
Sort
Discharge area is defined
Unwanted items are moved to discharge area
Items are organized to permit easy access to workers
An access system is in place with labels and color code to
identify
Straiten
Proper positioning of raw materials and tools
Materials or objects are always in their designed position
Fabrics, tools, and fixtures are well maintained and clean
Shine
Walls, floors, and moving equipments are shiny
Actions have been developed to remove source of wastes
Procedures are set to work on sort, straighten, and shine
Systematize 5S is run on a unit time basis
Working environment is healthy and pleasant
Standards are set and followed
Sustain
Goals of 5S have been achieved
Total score
Average score
5. Sustain and adhere to 5S standards
This is the last element of 5S. Production managers and other responsible bodies should set
standards adhered to 5S and make everyone follow them. Employees should be held accountable
for carrying out 5S actions and each worker at each area should make participating 5S tools as a
habit. And, in order to see the improvements, employee from the production plant should be
encouraged to take photographs or videos before and after 5S standards that recognize the
difference and provide them more motivation.
5. Conclusion
Pursuing Lean production tools and techniques in Ethiopian Textile and Garment industries may
be challenging but is a key to drastically minimize and eliminate Work-in-Process and any other
wastes from a production line. The main objective of this study was to pre-study and analyze the
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International Journal of Social Relevance & Concern (IJSRC)
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current production process and subsequently to explore and propose possible solutions in the
production process so as to substantially create smooth working environment and to improve
plant’s ability to produce products as per the customer demand.
This study explains the various aspects of the methodology and the importance of each step to
get the insight of the production process in a transparent way. Observation and check sheets were
the core methods to collect the necessary data and to enrich at analyzing and discussing the
results. According to the pre-study and analysis, the results shows that there is high inventory-inprocess and long production lead time, there is chance of dirty and delay of production
components, there is un-stabilized pace of production process to pace of customer demand, and
producing defective products is part of production capacity of the plant.
Finally, by adopting lean production principle it is possible to level production workload or
customer order in the production lineby scheduling the whole process units to produce products
in a synchronized pace, it is possible to reduce Work-in-Process, it is possible to minimize
production or manufacturing lead-time, and it is not difficult to achieve one-piece flow and to
produce the right product at the right time.
REFERENCES
[1] Agarwal, M. (2009), “Emerging Trends in Global Textile” [online], Available at:
http://www.fiber2fashion.com, [Date accessed: 25-11-2010]
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International Journal of Social Relevance & Concern (IJSRC)
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[2] Berihu, A. (2008), “Determinants of the Performance of the Garment Industry in Ethiopia”,
Applied Development Research, Ethiopian Development Research Institute, pp: 3-9
[3] James P., Daniel T., and Daniel R. (1990), “The Machine that Changed the World”,
Macmillan Publishing Company, New York, USA
[4] Fawaz, A. (2003), “Lean Manufacturing Tools and Techniques in the Process Industry with a
focus on Steel”, Published PhD thesis, School of Engineering, University of Pittsburg,
Pittsburg, USA, pp: 40-50
[5] Lean Enterprise Institute, (2009), “Introduction to Lean Production” [online], Available at:
http://www.lean.org,[Date accessed: 29-06-2011]
[6] Peter, H. and David, T. (2000), “Going Lean”, CF10 3EU, pp: 4-49
[7] William, M. (2001), “Lean Manufacturing Tools, Techniques, and How to Use them”, St.
Lucie Press Boca Raton, Washington DC, USA
[8] Ana, R. (2008), “Implementing Lean Manufacturing”: the Annals of “Dunărea De Jos” in
Machine Building, pp: 2-10
[9] Jon, M. (2004), “Know about Takt Time”, Gemba Research LLC, pp: 1-5
[10] Hiroyuki, H. (2009), “The Just-in-Time Production System, the Complete Guide to Just-inTime Manufacturing” JIT Implementation Manual, Vol. 1, pp: 14-50
[11] Lonnie, W. (2010), “How to Implement Lean Manufacturing”, MCGraw-Hill, New York,
USA
[12] Melanie, L. (2002), “Productivity Issues”, AACE International Transactions, Vol. 4, No. 2,
pp: 1-3
[13] James P. & Daniel T. (2003), “Lean Thinking”, CPI Bath London, U.K
[14] Mariana, P. (2008), “Improving the Control of Work-In-Process at VSM group AB”,
published masters’ thesis, TekniskaHogskolan, pp: 14-29
[15] Viswanadham, N. &Narahari, Y. (1998), “Performance Modeling of Automated
Manufacturing Systems”, Prentice-Hall of India Private Limited, New Delhi-110 001, India
[16] Groover, M. (1999), “Automation, Production Systems, and computer Integrated
manufacturing”, Prentice-Hall of India Private Limited, New Delhi-110 001, India
[17] Bill, C. (2005), “Lean Manufacturing that Works: Powerful tools for Dramatically Reducing
Waste and Maximizing Profit”, AMACOM, New York, USA.
[18] Lawrence, S. (2000), “Work Measurement and Methods improvement”, A WilleyIntersience Publication, New York, USA
[19] Kumar, B. (2008), “Industrial Engineering and Management”, KHANNA PUBLISHERS,
New Delhi, India
[20] Maynard, (2004), “Industrial Engineering Handbook”, MCGraw-Hill, New York, USA
© 2013, IOURNALS All Rights Reserved
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