line balancing article in Ethiopia case study on asbem garment plc

1. ADDIS ABEBA UNIVERSITY
INSTITUTE OF TECHNOLOGY
DEPARTMENT OF INDUSTRIAL
MANUFACTURING SYSTEM MODELING &
PERFORMANCE ANALYSIS TERM PAPER
Title: line efficiency improvement in asbem
garment plc
Prepard by id
Lioul mekonnen 5834/09
Submitted to Shimelis

2. 1. Abstract
The emergence of fast changes in fashion has given rise to the need to shorten production cycle
times in the garment industry. As effective usage of resources has a significant effect on the
productivity and efficiency of production operations, garment manufacturers are urged to utilize
their resources effectively in order to meet dynamic customer demand. This paper focuses
specifically on line balancing and layout modification. The aim of assembly line balance in
sewing lines is to assign tasks to the workstations, so that the machines of the workstation can
perform the assigned tasks with a balanced loading. Largest Candidate Rule Algorithm (LCR) &
Ranked Positional Weight (RPW) Method has been deployed in this paper.

3. 2. Introduction
Today’s business climate for clothing manufacturers requires low inventory and quick response
systems that turn out a wide variety of products to meet customer demand. It is especially in the
apparel industry that managers are trying to develop their current systems or looking for new
production techniques in order to keep pace with the rapid changes in the fashion industry.
In apparel enterprises a raw material is processed in different departments before becoming a
garment (Figure 1). There is no doubt that the sewing department is the most important
department in the whole firm. Because there are lot of different operations which are done
manually, the sewing department has to be under constant control. Consequently, all line
balancing processes which determine the speed of an assembly line are done in this department.
But it is a big mistake not to consider the relationship of the sewing department with other
departments.
Garment industry is one of the world’s major industries and the garment industry is a substantial
one within the supply chain of textile industry. The production process of garments is separated
into four main phases: designing/clothing pattern generation, fabric cutting, sewing, and
ironing/packing. The most critical phase is the sewing phase, as it generally involves a great
number of operations [1].
Industrial Engineers are concerned with the balance of the lines by assigning the tasks to
workstations as equally as possible. Unequal workload among workstations of a sewing line will
lead to the increase of both WIP and waiting time, indicating the increase of both production
cycle time and cost
The sewing line consists of a set of workstations in which a specific task in a predefined
sequence is processed. In general, one to several tasks are grouped into one workstation. Tasks
are assigned to operators depending on the constraints of different labor skill levels. Finally,
several workstations in sequence are formed as a sewing line. Shop floor managers are
concerned about the number of workstations. Inappropriate workstations assignment will leads to
the increase of labor cost, WIP, cycle time and poor throughput. These shop floor supervisors
arrange tasks to workstations based on their experience in practice. As a result, the line balance
performance cannot be guaranteed from one supervisor to another with different assignment
preference and/or work experience [2].
In manual-operations oriented system of garment manufacturing, there are different operations,
which are done manually. If the operation manager needs to develop a new system, he has to
observe the real system. However, closely observing the real garment manufacturing system is
difficult and expensive [4,5].

4. 3. Statement of the Problem
In the knit wear garment plant, the raw materials are processed in different departments and finally the
product shipped to the customers. Sewing department is the large and most important section in the
garment plant and the speed of the assembly process of the components would be under strong control.
The model proposed here is based on a reconfigurable production line to meet customer requirements as
well as improve system performances. In garment industry, any garment manufacturer tries the best to
finish the assembly work soon to increase on-time delivery to reduce production cost. Assembly line
balancing is therefore a critical issue for the efficiency and competitiveness. The main problem in asbem
garment industry is there is a working progress or delay of work due to line balancing problem and there
is no equal distribution of work in production line.
4. Literature review
Line Balancing means balancing the production line, or any assembly line. The main objective of
line balancing is to distribute the task evenly over the work station so that idle time of man of
machine can be minimized. Line balancing aims at grouping the facilities or workers in an
efficient pattern in order to obtain an optimum or most efficient balance of the capacities and
flows of the production or assembly processes. Assembly Line Balancing (ALB) is the term
commonly used to refer to the decision process of assigning tasks to workstations in a serial
production system. The task consists of elemental operations required to convert raw material in
to finished goods. Line Balancing is a classic Operations Research optimization technique which
has significant industrial importance in lean system. The concept of mass production essentially
involves the Line Balancing in assembly of identical or interchangeable parts or components into
the final product in various stages at different workstations. With the improvement in
knowledge, the refinement in the application of line balancing procedure is also a must. Task
allocation of each worker was achieved by assembly line balancing to increase an assembly
efficiency and productivity. Shop floor managers are concerned with the balance of the lines by
assigning the tasks to workstations as equally as possible. Unequal workload among
workstations of a sewing line will lead to the increase of both WIP and waiting time, indicating
the increase of both production cycle time and cost. In practice, the sewing line managers or
production controllers use their experience to assign tasks to workstations based on the task
sequence, labor skill levels and the standard time required to complete each task. As a result, the
line balance performance cannot be guaranteed from one manager to another with different
assignment preference and/or work experience [3].
Assembly line balancing is the problem of assigning various tasks to workstations, while
optimizing one or more objectives without violating any restrictions imposed on the line. ALBP
has been an active field of research over the past decades due to its relevancy to diversified
industries such as garment, footwear and electronics. The assembly line balancing problem has
received considerable attention in the literature, and many studies have been made on this subject
since 1954. The assembly line balancing problem was first introduced by Bryton in his graduate

5. thesis. In his study, he accepted the amount of workstations as constant, the workstation times as
equal for all stations and work tasks as moving among the workstations. The first article was
published in 1955 by Salveson. He developed a 0-1 integer programming model to solve the
problem. COMSOAL (Computer Method of Sequencing Operations for Assembly
Lines).Configurations of assembly lines for single and multiple products could be divided by
three line types, single-model, mixed-model and multi-model. Single-model assembles only one
product, and mixed-model assembles multiple products, whereas a multi-model produces a
sequence of batches with intermediate setup operations [6].
ALBP with various objectives are classified into three type.
 ALBP-I: Minimizes the number of workstations, for a given cycle time.
 ALBP-II: Minimizes the cycle time, for a given number of workstations.
 ALBP-III: Maximizes the workload smoothness, for a given number of workstations.
Balancing assembly lines becomes one of the most important parts for an industrial
manufacturing system that should be supervised carefully. The success of achieving the goal of
production is influenced significantly by balancing assembly lines. Since then, many industries
and for sure researchers, attempt to find the best methods or techniques to keep the assembly line
balanced and then, to make it more efficient. Furthermore, this problem is known as an assembly
lines balancing problem . An assembly line consists of workstations that produce a product as it
moves successively from one workstation to the next along the line, which this line could be
straight, u-line or parallel until completed. To balance an assembly line, some methods have
been originally introduced to increase productivity and efficiency. These objectives are achieved
by reducing the amount of required manufacturing time to produce a finished product, by
reduction in number of workstations or both of them [7].
This paper solves single-model line balancing problem with real application. As a result, for
practical consideration, this paper focuses on the real case of an assembly line in garment
manufacturing.
An assembly line consists of workstations that produce a product as it moves successively from
one workstation to the next along the line, which this line could be straight, u-line or parallel
until completed. To balance an assembly line, some methods have been originally introduced to
increase productivity and efficiency. These objectives are achieved by reducing the amount of
required manufacturing time to produce a finished product, by reduction in number of
workstations or both of them [8].
The Largest Candidate, Kilbridge and Wester (column) and Ranked Positional Weights (RPW)
are different heuristic methods commonly utilized to arrange and distribute the description
element time along the workstations in the system. Each of those methods could be results in a
different type of workstations layout [9]. This study involved applying the first heuristic

6. algorithms to study the process planning gaining a reduced production time. In this paper, largest
Candidate Rule (LCR), balancing method is selected for polo shirt Assembly Line balancing.
Balancing assembly lines becomes one of the most important parts for an industrial
manufacturing system that should be supervised carefully. The success of achieving the goal of
production is influenced significantly by balancing assembly lines. Since then, many industries
and for sure researchers, attempt to find the best methods or techniques to keep the assembly line
balanced and then, to make it more [10]
Balancing assembly lines becomes one of the most important parts for an industrial
manufacturing system that should be supervised carefully. The success of achieving the goal of
production is influenced significantly by balancing assembly lines. Since then, many industries
and for sure researchers, attempt to find the best methods or techniques to keep the assembly line
balanced and then, to make it more efficient. Furthermore, this problem is known as an assembly
lines balancing problem [11]. An assembly line consists of workstations that produce a product
as it moves successively from one workstation to the next along the line, which this line could be
straight, u-line or parallel until completed. To balance an assembly line, some methods have
been originally introduced to increase productivity and efficiency. These objectives are achieved
by reducing the amount of required manufacturing time to produce a finished product, by
reduction in number of workstations or both of them [12]

7. 4.1 Literature rivew summery
Author tools Problem Methods
Yi-Jhen Lin, Chun-Ju
Lin, and Tiffany Y.
Chen, 2014
Encoding, assigning
Genetic operators, Initial
solution, Experimental
Results, Parameter setting
Assembly line
balancing problem
(ALBP)
grouping genetic
algorithm, tables
Dividing the labor’s
according to their skill
level
Md. Niaz Morshed &
Kazi Saifujjaman
Palash, 2014
Calculation of cycle time
of process, identifying the
non –value added
activities, calculating total
work load on station and
distribution of work load
on each workstation by
line balancing
line efficiency
problems
Flowchart for line
balancing, control
chart, tables
Naveen Kumar &
Dalgobind Mahto,2013
Heuristic line balancing
problem
Ranked Positional
Weight (RPW) Method
MASARU NAKAJIMA,
SEI UCHIYAMA, AND
YOSHITO MIURA, 1980
Heuristic Line effchincey
problems
Largest Candidate Rule
(LCR) Method
MUCELLA G. GUNER
AND CAN UNAL, 2008
Work sharing method Labor product ivy
improvement
Hybrid algorithm
GHOSH, S., & GAGNON,
R. J, 1989
Simulation long production
lead time,
bottlenecking
Arena software
M. Z. MATONDANG
AND M. I. JAMBAK
(2010)
Simulation Line balancing
problem
Largest Candidate
Rule Algorithm
(LCR)
N ISMAIL, G. R.
ESMAEILIAN, M.
HAMEDI, AND S.
SULAIMAN (2011)
Heuristic
Line balancing
problem
WITH MIXED-MODEL
PRODUCT
M.P. GROOVER,(2008), Largest Candidate Rule
Algorithm (LCR)
Efficiency problems Computer integrated
manufacturing
M. Z. MATONDANG
AND M. I. JAMBAK
(2010) “
Ranked Positional Weight
(RPW) Method
Line balancing
problem
Computer tequniques
SOTIRIOS G.
DIMITRIADIS(2006)
Heuristic method Line efficiency
problems
GROUPS OPERATING O
THE SAME PRODUCT
AND WORKSTATION
NILS BOYSEN , MALTE
FLIEDNER AND ARMIN
SCHOLL(2007)
Simulation Bottleneck
operation
Arena software

8. Objective of the study
General objective: by using line balancing to increase productivity of asbem garment plc.
Specific objective
 To know the capacity of the company
 To know the processing time of the polo shirt product
 To know the production rate.
 Identification of bottleneck area.
Scope of the study
The scope of this study is on assembly line balancing in asbem garment plc and improving
efficiency on asbem garment plc and the main area is in sewing section of production and
improving line efficiency.
5. Methodology.
A garment order is chosen which was started in that line, knowing total amount of order, style
description,andfabrictype and color. I have recorded the time to make each process for each and every
worker to find out the number of operator and helper, type of machines and individual capacity. To find
out the(standard minute value ) S.M.V , process wise capacity has been calculated, in addition to that I
have calculated the target, benchmark capacity, actual capacity line graph, labor productivity and line
efficiency.. In this project I proposed a method to balance the line by sharing workload among equally
adept workers who has experience in both the bottleneck process and balancing process. After balancing,
new manpower has been proposed and final capacity of each worker has been reallocated. I have
compared the line graph after balancing the line, labor productivity and line efficiency. Finally a proposed
production layout has been modeled with balanced capacity.
The data has been collected from asbem garment plc knit wear garment section on basic polo-shirt
production line. In the plant, there are 11 work elements or tasks to complete the production of the basic
polo- shirt and for each of them the workstation time is recorded using the stopwatch. For each work
element, the time is recorded 5 times to determine the time variability distribution and operator
performance consistency and I use the average time.
Data collection method
 Primary data collection: Direct observation system for time study.
 Secondary data collection: factory documents and internet to review the articles and
books which help for our term paper.

9. Process Sequence of Polo-shirt Manufacturing
Placket preparation
Front and back Placket cutting
Collar preparation shoulder top stitch stitch placket
Top stitch
Shoulder stitch
Collar closing placket closing
Collar stich placket attaching
sleeve preparation collar attach
cuff hem stich
Side attach
cover stich
Sleeve attach
Bottom hem stitch
Button hem cutting
Button hole making
Button fixing
OPERATION BRAKEDOWN OF POLO-SHIRT PROUCT

10. 6. Data analysis
I use the Body making and assembling part to balance the line the other operation are making
preparation for the assembly line. So I use 11 operations.
 So i have to differentiate where the bottle necks are:
no Operations SMV Machine type precedence Work station
1 Shoulder join with tape 1.49 Over lock 0 1
2 Placket attach with body 1.25 1N Lock Stitch 1 1
3 Button hole on upper placket 1.06 Button holer 1,2 2
4 Button attach on lower
placket
1.17
Button Stitcher
1,2,3 2
5 Right side seam 1.34 Over lock 1 3
6 Bottom hemming 1.2 Flat lock 1,5 3
7 Left side seam with care label 0.45 Over lock 1,5,6 4
8 Both sleeve attach 0.21 Over lock 1 4
9 Collar join 0.28 1N Lock Stitch 1,2,3,4 4
10 Back tacing 0.29 1N Lock Stitch 1,8 4
11 Bottom tuck 0.76 1N Lock Stitch 7,10,9 4
 Work Element time and Precedence at Present Assembly Line
Operation Time Work station
1 2 2.74 1
3 4 2.13 2
5 6 2.63 3
7 11 2.0 4
Prisidence diagram
1
5
8
2
43
76
11
9
10

11. Calculation of existing assembly line
No of operator = 11
Cycle time(c) = 3min
Demand rate = 160
1Shift per day = 8hr
No of work station(m) =4
Sum of station time (STi)= 9.5
Line efficiency = * 100 = 9.5 = 79%
M*C 4*3
Smoothness index = (cycle time –each task time )2 = 7.27
Expected no of production = D*SH = 300*480 = 48000 polo shirt per year
CT 3
Heuristic Methods
After studying Present Assembly line if we want to increase production rate so minimize cycle
time from 3 to 2.85 min for a given number of stations (m). The method to improve production
rate by minimizing cycle time is discuss below.
6.1 Ranked Positional Weight (RPW) Method
The ranked positional weight method used and computed for each element. The method
accounted for Tek value and its position in the precedence diagram The RPW is calculated by
summing Tek and the other times for elements that follow Tek in the arrow chain of the
precedence diagram Then rearrange the values of time using the previous steps, work elements
are listed according to RPW value in Table.
 Work Element Arranged According to RPW

12. no Operations SMV Machine type precedence RPW in
descending order
1 Shoulder join with tape 1.49 Over lock - 9.5
2 Placket attach with body 1.25 1N Lock
Stitch
1 8.25
3 Button hole on upper placket 1.06 Button holer 1,2 6.76
4 Button attach on lower
placket
1.17 Button
Stitcher
1,2,3 5.7
5 Right side seam 1.34 Over lock 1 4.53
6 Bottom hemming 1.2 Flat lock 1,5 3.19
7 Left side seam with care label 0.45 Over lock 1,5,6 1.99
8 Both sleeve attach 0.21 Over lock 1 1.54
9 Collar join 0.28 1N Lock
Stitch
1,2,3,4 1.33
10 Back tacing 0.29 1N Lock
Stitch
1,8 1.05
11 Bottom tuck 0.76 1N Lock
Stitch
7,10,9 0.76
Work Element Assigned to Station According to Tek values for RPW
no Operations HIGH
SMV
Machine type precedence Work station
1 Placket attach with body 1.49 1N Lock Stitch - 1
5 Right side seam 1.34 Over lock 1 1
2 Shoulder join with tape 1.25 Over lock 1 2
6 Bottom hemming 1.2 Flat lock 1,5 2
3 Button attach on lower
placket
1.06
Button Stitcher
1,2,3 3
4 Button hole on upper placket 1.17 Button holer 1,2 3
8 Bottom tuck 0..21 1N Lock Stitch 1 4
7 Left side seam with care label 0.45 Over lock 1,5,6 4
10 Back tacing 0.29 1N Lock Stitch 1,8 4
9 Collar join 0.28 1N Lock Stitch 1,2,3,4 4
11 Both sleeve attach 0.76 Over lock 7,10,9 4
Line efficiency = * 100 = 9.5 = 83.3%
M*C 4*2.85
Expected no of production = D*SH = 300*480 = 50,526 polo shirt per year.
CT 2.85

13. 6.2 Largest Candidate Rule (LCR) Method
In this approach work elements were arranged in descending order according to their Tek
values.Worker was assigned by elements at the first workstation by starting at the top of the list
and selected the first element that satisfies precedence requirements and does not causing the
total sum of Tek at that station to exceed the allowable C when an element is selected for
assignment to the station, started backward at the top of the list for the subsequent assignments.
The procedure then followed by stating that no more elements could be assigned without
exceeding C and proceeded to the next station. Consequently, repeating the previous steps for as
many additional stations as possible until all elements have been assigned as shown in the
precedence diagram.
no Operations HIGH
SMV
Machine type precedence Work station
1 Placket attach with body 1.49 1N Lock Stitch - 1
5 Right side seam 1.34 Over lock 1 1
2 Shoulder join with tape 1.25 Over lock 1 2
6 Bottom hemming 1.2 Flat lock 1,5 2
3 Button attach on lower
placket
1.17
Button Stitcher
1,2,3 3
4 Button hole on upper placket 1.06 Button holer 1,2 3
8 Bottom tuck 0.76 1N Lock Stitch 1 4
7 Left side seam with care label 0.45 Over lock 1,5,6 4
10 Back tacing 0.29 1N Lock Stitch 1,8 4
9 Collar join 0.28 1N Lock Stitch 1,2,3,4 4
11 Both sleeve attach 0.21 Over lock 7,10,9 4
Line efficiency = * 100 = 9.5 = 83.3%
M*C 4*2.85
Expected no of production = D*SH = 300*480 = 50,526 polo shirt per year.
CT 2.85

14. 7. Result and discussion
Comparison of Two Methods
Comparison of Result obtained from above Methods Sr No Parameter Present Assembly Line
No Parameter Present assembly
line
RPW method LCR method
1 Cycle time (min) 3 2.85 2.85
2 Line efficiency 79% 83.3 83.3
3 Production rate
per year
48,000 50,526 50,526
4 No of work
station
4 4 4
 Before line is balanced
Price of one polo shirt is 100
Total produced per year is 48,000
= 48,000*100
=4,800,000ETB/year
 After the line is balanced
Total produced per year is 50,526
=50,526*100
=5,052,600ETB/day
 Profit per year is
5,052,600 – 4,800,000
= 252,600 birr per year saved

15. Conclusion
Result would have been more effective if we would have taken some large quantity order and
balancing the process is highly related to the type of machines as machine utilized in bottleneck
and balancing process should be similar. Further improvements in the productivity can be
achieved by considering large amount of order minimum.
After applying balancing methods to existing assembly line by reducing cycle time 3 min to 2.85
min then methods give a more efficient assignment of work element with improvement of line
efficiency from 79 % to 83.33 %, increase production rate of 48000 units to 50526units and they
get 252,600 birr per year profit. So any one method from above two methods is applicable for
balancing of existing assembly line because of very slight difference.

16. Recommendation
In this research only a serial production line is considered. However, production lines with
parallel workstations or feedback facilities can be done as well. Considering possibility of
detecting nonconformities within the production line, dependent defects and/or the imperfect
inspection facilities can also be considered for extending the in future.
 The company must use different method of line balancing
 The company must give training for the employee
 The company should consider the line efficiency to increase the productivity of the
company.

17. Reference
[1] Yi-Jhen Lin, Chun-Ju Lin, and Tiffany Y. Chen , Assembly line balancing International Conference
on Industrial Engineering and Operations Management Bali, Indonesia, January 7 – 9, 2014
[2] Md. Niaz Morshed & Kazi Saifujjaman Palash, Assembly Line Balancing, Global Journal of
Researches in Engineering: G Industrial Engineering Volume 14 Issue 3 Version 1.0 Year 2014
[3] Naveen Kumar & Dalgobind Mahto, Assembly Line Balancing, Global Journal of Researches in
Engineering Industrial Engineering Volume 13 Issue 2 Version 1.0 Year 2013
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[9] M.P. GROOVER, (2008), “AUTOMATION, PRODUCTION SYSTEMS, AND COMPUTER-INTEGRATED
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