Improvement of Sewing Line Productivity by Using Work Study Method

Md. Fahim Hossan¹, Yousuf Hossain and Mehedi Hasan
Department of Textile Engineering
Northern University Bangladesh
Email: hossanfahim36@gmail.com¹

Abstract
In Bangladesh, garment manufacturing sector plays a vital role for economy development. Productivity improvement can be helped to enrich profit of garment industry by minimizing excess work and developing new method for particular operation. Nowadays, productivity improvement is a popular topic for any kinds of industry. So that improving productivity is one of the main concerns of garments products industries. Work study is one of the most important tools that can help to increase productivity in sewing line in the readymade garments industry. Hence, this study helps to identify the bottleneck and suggest appropriate system to improve productivity. For this purpose, method study has been carried out by applying questioning techniques concept where recording and critical analysis of all related information has been performed in particular production line. As a result, considerable amount of work content is reduced in the new improved method. Then time study has been taken by stopwatch and determined the basic time for all operation sequences and the capacity of each workstation per day has been calculated. By applying method study and work measurement in the industry at production for T-shirt productivity has been improved by 2.48%.

CHAPTER 01
INTRODUCTION

1.1 Introduction
As a supply chain of textile industry, garment industry is one of the major industries of The world. The production process of garments is separated into four main phases: Designing/ clothing pattern generation, fabric spreading and cutting, sewing and ironing and packing. The most critical phase is sewing phase. As the sewing is the heart of apparel industry, we have to design the sewing line properly so as to achieve the best output at maximum efficiency. Apparel is a mass production system. Assembly line production systems are developed to meet the requirement of mankind, which continue to grow day by day. The demand for greater product variability and shorter life cycles has caused traditional production methods to be replaced with assembly lines. Assembly line is an industrial arrangement of machines, equipment’s and workers for continuous flow of work prices in partitioning the total amount of work into a set of elementary operations called tasks. Task reassigned to operators depending on constrains of different labor skill levels. Finally, several workstations in sequence are formed as a sewing line.

The sewing process includes a set of work stations, at each of which a specific task is carried out in a restricted sequence, write hundreds of employees and thousands of bundles of sub assemblies producing different style simultaneously. Therefore this process is of cortical importance and needs to be planned more carefully. As a consequence, good line balancing with small stocks in the sewing line has to be drawn up to increase the efficiency and quality. So the aim of assembly line balancing in sewing line is to assign tasks to the workstations, so that the machines of the workstation can perform the assigned task with a balanced loading with different labor skill levels.

1.2 Objectives

To know the function of working aids are used in garments industry.
To identify scope in a sewing machine where working aids can be used
To compare the efficiency before using working aids and after using working aids.
To time study and method study of different garments
To set target production lower cost.

CHAPTER 02
LITERATURE REVIEW

2.1 Line Balancing
A line is defined as a group of operators under the control of one production supervisor. Balancing is the technique of maintaining the same level of inventory at each and every operation at any point of time to meet the production target and to produce garments of acceptable quality. It is a function of the work study office to provide management with information to help the efficient and productive running of the factory, and part of this information is the process known as line balancing. Line balancing is a vital key in the efficient running of a line.

The objective of the process is to balance the workload of each operation to make sure that the flow of work is smooth, that no bottlenecks are created, and that the operators are able to work at peak performance throughout the day. This process is intended to reduce waiting time to a minimum, or in fact with the use of some work in progress (WIP) to eliminate waiting time completely. The process to balance the line is given below:

In operation breakdown we try to equalize the standard time.
But still there will be the difference in the standard time which leads to work in progress.
So, we try to set the flow through each operation to be similar as possible.
Checking from time to time to see how things are going and then making adjustments to even out the flow again. This process is called balancing.

2.2 Objectives of Line Balancing
Match the production rate after all wastes have been removed to the talk time at each Process of the value stream.

Regular material flow.
Maximum uses of man power and machine capacity.
Minimum process time.
Minimizing slack time.
Minimizing workstation.
Maximum output at the desired time.
Quality maintenance of the garment.
Reduce production cost.

2.3 Importance of Line Balancing

Line balancing helps to know about new machine required for new style.
It becomes easier to distribute particular job to each operator.
It becomes possible to deliver goods at right time at the agreed quality for list cost.
Good line balancing increase the rate of production.
Line balancing helps to compare the required machinery with the existing one and compare balance.
It also helps in the determination of labor requirement.
Good balancing reduces production time.
Profit of a factory can be ensured by proper line balancing.
Proper line balancing ensured optimum production at the agreed quality.

2.4 Goals for Balancing
There are many goals of line balancing they are given below

Meeting production schedule.
Avoiding the waiting time.
Minimizing over time.
Protecting operator earning.

2.5 Process to Balance the Time
The balancing of the time is necessary to balance the line, so the process of balancing the time is to be followed as given in the points here.

Knowing work available at the start of the day.
Planning transfer needed to compensate for any know absenteeism.
Checking attendance at the start of the day.
Making additional assignments to compensate unexpected absentees.
Making periodic checks during the day to check production.

2.6 Points to be Noted When Making Balancing

Meeting production target by usage of
- Regular operators,
- Utility operators,
- Shuttle operators.
Work flow should be constant throughout all operations.
Avoiding over time.
Determining human resource.
Checking absence daily.
Updating daily production every two hours.

2.7 Process to Start Balancing the Production Line

Allocating operators based on the planned efficiency.
Determining the amount of work in process required to ensuring smooth flow.

2.8 Steps to Balance the Line
The method of line balancing can vary from factory to factory and depends on the garments manufactured; but at any instance, line balancing concerns itself with two distinct applications. “Opening the line” and “Operating the line”.

2.8.1 Opening the line
Opening the line means the operations that are done to obtain a basic of the line or the collection or establishment of a semi balanced line before final balancing. The processes of opening the line are given here.

Calculation of labor requirements.
Operation breakdown.
Opening the line Theoretical operation balance.
Initial balance.
Balance control.

2.8.2 Operating the line
Operating the line means the successful running of the line to always keep the balance in progress of the production.

Opening the line and operating the line is significant steps to balance the line for any further production in a single or multiple production lines. Though it varies from different production system the application signifies to balance properly.

2.9 Work Study:
Work study is the systematic examination of the method of carrying activities, so as to input the effective use of resources and to setup standards and performance for the activities being carried out. Management frequently all on specialist to assist it in improving productivity. One of the most powerful tools they can use is that of Work-study.

2.10 History of Work Study in Bangladesh
Activities of work study in textile and apparel industry are done by industrial engineering department. Actually, work study is used for measuring work. Industrial engineering department is responsible for work study in the garment industry. Work study is the most important tool for controlling production and improving productivity.

It is a new concept in textile and apparel industry. We can define work study in the following way. Work study is the investigation of the work done in an organization by means of a consistent system in order to attain the best utilization of men, machines and materials at a period of time. According to ILO, Work study is used to embrace the techniques of method study and work measurements which are employed to ensure the best possible use of human and available resources in carrying out a specified activity. Mr. Keith Harding form England started Work Study in Bangladesh (Young one Corporation) in 1991. Now it is contributing very well to increase the productivity in Bangladesh.

2.11 Father of Work Study
Mr. FW (Frederic Winslow) Taylor who is called the father of scientific management is the founder of work-study. During the Second World War USA needed so many arms within a short time. Then Mr. FW Taylor applied Work-Study method to make many arms in short time and go tremendous result. After that work-study is being used in everywhere. Now it is circumference is getting larger day by day.

2.12 Components of Work Study

2.13 Characteristic of Work Study Engineer
A work study engineer need to be educated, expert, smart, confident, personal dignity and honest. Details below-

2.13.1 Sincerity and Honest:
The work study person must be sincere and honest only if is the case will he / she gains the confidence and respect of those with whom he or she will work.

2.13.2 Enthusiasm:
He/she must be really keen on the job, believe in the importance of what he or she is doing and be able to transmit enthusiasm to the people round about.

2.13.3 Tact/ Diplomacy:
Tact is dealing with people comes from understanding them and wishing to hurt their feeling by unkind or thoughtless word, even when these may be justified. Without justified no work study person is going to get very far.

2.13.4 Good Appearance:
The person must be neat tidy and look efficient. This will inspire confidence among the people with whom he or she has to work.

2.13.5 Self-Confidence:
This can only come with good training and experience of applying work study successfully. The work study practitioner must be able to stand up to top management, supervisors or workers in defense of his opinion and finding, and to do so in such a way that will respect and not give offence.

2.14 Calculate SAM and SMV of a Garment
SAM and SMV are units of measuring standard minutes of a task or an operation of a garment. Where, SAM stands for Standard Allowed Minutes and SMV stands for Standard Minute Value.

When someone says sewing SMV of garment is 15 minutes, it means that particular garment should take 15 minute to complete sewing task by a standard worker. Garment SMV is summation of SMV of number of operations those are performed to make the garment.

2.15 Method of Calculating SMV

Calculation of SMV Using Synthetic Data
Calculation of SMV through Time Study.

2.15.1 Calculation of SMV Using Synthetic Data:
In this method ‘Predetermined Time Standard’ (PTS) code are used to establish ‘Standard Time’ of a garment or other sewing products.

Step 1: Select one operation for which you want to calculate SMV.

Step 2: Study the motions of that operation. Stand by side of an operator (experienced one) and see the operator how he is doing it. Note all movement used by the operator in doing one complete cycle of work. See carefully again and recheck your note if all movement/motion are captured and correct. (For example motions are like – pick up parts one hand or two hands, align part on table or machine foot, realign plies, etc).

Step 3: List down all motion sequentially. Refer the synthetic data for TMU (Time measuring unit) values. For synthetic data you can refer GSD (without license use of GSD code prohibited but for personal use and study one can refer GSD code and TMU values) or Sewing Performance Data table (SPD). Now you got TMU value for one operation (for example say it is 400 TMU). Convert total TMU into minutes (1 TMU=0.0006 minute). This is called as Basic Time in minutes. In this example it is 0.24 minutes.

Step 4: Standard minutes value (SMV) = (Basic minute + Bundle allowances + machine and personal allowances). Add bundle allowances (10%) and machine and personal allowance (20%) to basic time. Now you got Standard Minute value SMV.

SMV = (0.24+0.024+0.048) = 0.31 minutes.

2.15.2 Calculation of SMV through Time Study:

Formula:

SMV = Basic time + Allowance
Basic time = Cycle Time X Performance Rating

Terms:

Basic Time: Basic time is the required time a qualified operator to complete a job when he /she works at standard performance (at 100% rating).

Observed Time: Time required by a qualified work study officer by observing a regular worker while he/she doing a task.

Rating: Rating is the assessment of a worker rate of working relative to observer’s concept of the rate corresponding to standard pace. Rating depends on skill, speed, effort and dexterity of the operator.

Standard rating: The standard rate is the qualified workers are assumed to be able to work provided they are motivated to do the job and if right method of work is applied such rate is called as standard rating. This standard rate corrects to 100 in the rating scale.

2.16 Procedure of SMV Calculation through Time Study

Step 1: Select one operation for which you want to calculate SMV.

Step 2: Take one stop watch. Stand by side of the operator. Capture cycle time for that operation. (cycle time – total time taken to do all works needed to complete one operation, i.e. time from pick up part of first piece to next pick up of the next piece). Do time study for consecutive five cycles. Discard if found abnormal time in any cycle. Calculate average of the 5 cycles. Time you got from time study is called cycle time. To convert this cycle time into basic time you have to multiply cycle time with operator performance rating. [Basic Time = Cycle Time X Performance Rating]

Step 3: Performance rating. Now you have to rate the operator at what performance level he was doing the job seeing his movement and work speed. Suppose that operator performance rating is 80%. Suppose cycle time is 0.60minutes.

Basic time = (Cycle time X rating) = (0.60 X 80%) = 0.48 minutes

2.17 Calculate Efficiency of a Production Batch Or Line
Like individual operator efficiency, efficiency of a production line or batch or section is important for a factory. Daily line efficiency shows the line performance. To calculate efficiency of a line for a day, you will need following data (information) from the line supervisor or line recorder.

Number of operator-how many operators worked in the line in a day.
Working hours (Regular and overtime hours)-how many hours each of the operators worked or how many hours the line run in a day.
Production in pieces-how many pieces are produced or total line output at the end of the day.
Garment SAM-what is exact standard minute of the style (garment).

Once we have above data, we have to calculate following using above information

Total minutes produced by the line: To get total produced minutes multiply number of operators by daily working hours.

2.18 Calculate Operator Worker Efficiency
In apparel manufacturing, skill and expertise of a sewing operator is being presented in “Efficiency” term. An operator with higher efficiency produces more garments than an operator with lower efficiency in the same time frame. When operators work with higher efficiency, manufacturing cost of the factory goes down.

Secondly, factory capacity is estimated according to the operator efficiency or line efficiency. Hence, efficiency is one of the mostly used performance measuring tools. So how do you calculate operator efficiency in factory? To calculate operator efficiency, we will be needed standard minutes (SAM) of the garment an operation our operator is making. Use following formula and calculate operator efficiency.

2.18.1 Efficiency calculation formula:

Efficiency % = [(production x SMV)/ (Manpower x Working Hour)] x 100

2.19 Productivity
The definition of productivity is given as “OUTPUT” compared to “INPUT”. According to Marsh, Brush (2002) in his article Journal of industrial technology, productivity is a measure of the efficiency and effectiveness to which organizational resources (inputs) are utilized for the creation of products and/ or services (outputs). Productivity measurement is both a measure of input utilization and an assessment as to whether or not input utilization is growing faster than output.

In the case of a garment manufacturing factory, “output” can be taken as the number of products manufactured, whilst “input” is the people, machinery and factory resources required to create those products within a given time frame. The key to cost effective improvements in output- in “productivity”- is to ensure that the relationship between input and output if it comes only as a major increase in input. Indeed, in an ideal situation, “input” should be controlled and minimized whilst “output” is maximized.

Higher productivity provides more products from the same number of people, in the same time frame. This in turn improves “overhead recovery” related to factory costs, such as electricity and fuel, because overheads are fixed within that frame. So, the more products produced in a given time frame the less overhead allocation per product, which, in turn reduces the cost of each individual item and therefore improves competitive edge.

Dr. Bheda in his book “managing Productivity in the Apparels Industry” explained the different ways of measuring productivity. Productivity can be expressed in many ways but mostly productivity is measured as lab our productivity, machine productivity or value productivity. These three terms can be defined as-

Lab our productivity – Output per labor (direct + indirect) in a given time frame (in pieces).
Machine productivity –output per machine in a given time frame (in pieces).
Value productivity –Total value of output in a given time frame.

CHAPTER 03
METHODOLOGY

3.1 Methodology
For this experiment one garment (t-shirt) have been chosen. After that time and method study is conducted according to the process sequences. Then find out the flaws in the system which reduces the productivity. Then those processes are improved by replacing higher efficient worker, improving the method and installing higher speed machine. After that, time study is again conducted to see the difference between before and after SMV to check that the productivity of different garments has been improved or not. Work measurement can be defined as the implementation of a series of techniques which are designed to find out the work content, of a particular task or activity, by ascertaining the actual amount of time necessary for a qualified worker, to perform the task, at a predetermined performance level. We can use to Work measurement system.

3.2 Materials Used
Required tools

Stop watch
Observation Sheet
Study Board
Study Form
Reading machine
Slide Ruler
Measurement Tape
Micrometer
Motion Picture Equipment
Pencil
Eraser
Item Information

3.3 Making Process of T-shirt

3.4 Equations Used for Calculation

Standard Pitch Time (S.P.T) = Basic Pitch Time (B.P.T) + Allowances (%)

Target = Total manpower × working hour×60×efficiency/SMV.

Theoretical Manpower = Target per hour/Process capacity per hour.

Line Labor Productivity = Total number of outputs per day per line/Number of workers worked.

Line Machine Productivity = Total number of outputs per day per line/number of machines used.

Line Efficiency = Total output × SMV/Total manpower × working hour×100%

SMV = Standard Minute Value
= Basic Time + Allowance of Basic Time
= (Cycle Time × Rating of Operator) + Allowance Of Basic Time.

Factory Capacity = (60 ×Average SMV) × Total Direct Worker × Work Hour × Work Days × Efficiency (%).

Productivity = (Output / Input) × 100

Achievement (%) = Total Production / Total Target

Balancing Loss (%) = 100% − Required Manpower/ Allocated Manpower. Basic Pitch Time (BPT) = Total SMV / Total Manpower

Tact Time = Total SMV / Total Manpower

Upper Control Limit (UCL) = BPT / Expected Efficiency (%) Lower Control Limit (LCL) = 2 × BPT – UCL

DHU = Total Number of Defect Total Number of Garments × 100

Defects per hundred units = (Total defects found × 100)/Total garments inspected

AML = Individual SMV / BPT ٫

AML = Actual Manning/Machine Level

TML = Individual SMV BPT

TML = Theoretical Manning/Machine Level

OEE = Operative Rate × Performance Rate × Quality Rate
= Operating Time /Active Time × Input × Ideal Cycle Time / Operating Time × Good Output Product / Input
= Ideal Cycle Time × Good Output Product / Active Time
= Valuable Operating Time /Active Time

CPM = Total overhead cost for the month/ No of SMV earners × working Minute’s × efficiency.

Capacity = 60 / Capacity time in minute Cycle Time

Cycle Time = 60 / Team target

Team target = (Work hour/SMV) × Present operator × Organizational efficiency

Capacity Achievable = Capacity × Balance

Balance = BPT / Bottle neck time (BNT)

Standard time = Net operation time × (1+ratio of loss time)

Daily output = Work hour / SMV

Factory capacity = (Work hour / SMV) × Total worker × Working day × Efficiency

CPM = (Total overhead cost of the month / No of SMV earners × Work minutes)

Required no of operator = Target daily output / Daily output per operator

CM of garments = Total production / (No of worker × Work hour)

Marker Efficiency = (Total area of marker / Total area of lay) × 100

CPD = Consumption per dozen

CPD = Marker length × Marker width × GSM × 12 / (1000 × 100 × 100 × Total marker Pace€™s)

CHAPTER 04
RESULT and DISCUSSION

4.1 Graphical Representation of SMV before Line Balancing
Here by analyzing worker psychology line condition existing workers was motivated and trained to work, ore consciously and efficiently. In this case before balancing the line operation 27 and production per hour 231pcs, was eliminated by disturbing their work load within the worker who processes higher capacity. Some operation gives low production and some operation gives high production but we selected average equal point production in graphical diagram. Before line balancing graphs some operation we mark different color and calculative SMV.

4.2 Graphical Representation of SMV after Line Balancing
In the above graph we can see the operation 23 and production per hour 249pcs. Some operation gives low production and some operation gives high production but we selected average equal point production in graphical diagram. After line balancing graphs some operation we mark deferment color and calculative SMV.

4.3 SMV Calculation (Before line balancing)

1. Front and back part match = 11+ (11*15%)
= 11+ 1.65 = 12.65 /60 = 0.21

2. 1st shoulder join = 11.5+ (11.5*15%)
= 11.5+1.72=13.22/60 = 0.22

3. Join w. Folder = 10.7+ (10.7*15%)
= 10.7+1.60= 12.30/60 = 0.20

4. Neck nose tack =10.4+(10.4*15%)
=10.4+1.56 = 11.96/60 = 0.19

5. Neck Back tap = 10.5+ (10.5*15%)
= 10.5+1.57= 12.07/60 = 0.20

6. Thread trimming = 10.5+ (10.5*15%)
= 10.5+1.57= 12.07 /60 = 0.20

7. Front neck top stitch = 10.5+ (10.5*15%)
= 10.5+1.57= 12.07/60 = 0.20

8. Back neck top stitch = 19.9+ (19.9*15%)
= 19.9+2.98= 22.88/60= 0.38

9. Thread trimming and body arrange =11.5+ (11.5*15%)
= 11.5+1.72=13.22/60 = 0.22

10. 2nd shoulder join = 11+ (11*15%)
= 11+ 1.65 = 12.65 /60 = 0.21

11. Shoulder Inner and Outer tack = 12.6 + (12.6*15%)
= 12.6+1.89 =14.49/60 = 0.24

12. Shoulder Scissoring = 11.5+ (11.5*15%)
= 11.5+1.72=13.22/60 = 0.22

13. Sleeve Penal join = 24+ (24*15%)
= 24+3.6 = 27.6 / 60 = 0.46

14. Care label attach = 12.6 + (12.6*15%)
= 12.6+1.89 =14.49/60 = 0.24

15. Mark sleeve fold tack (side) = 21+(21*15%)
= 21+3.15= 24.15/60 = 0.40

16. Sleeve fold tack (mid) = 19.9+ (19.9*15%)
= 19.9+2.98= 22.88/60= 0.38

17. Sleeve join = 19+ (19*15%)
= 19+ 2.85= 21.85 /60 = 0.36

18. Thread trimming and body arrange = 12+ (12*15%)
= 12+ + 1.8 = 13.8 /60 = 0.23

19. Side Seam Join = 27 + (27*15%)
= 27+ 4.05 = 31.05 /60 = 0.51

20. Sleeve Inner Tack = 12.6 + (12.6*15%)
= 12.6+1.89 =14.49/60 = 0.24

21. Sleeve outer Tack = 11.5+ (11.5*15%)
= 11.5+1.72=13.22/60 = 0.22

22. Body arrange = 11.5+ (11.5*15%)
= 11.5+1.72=13.22/60 = 0.22

23. Bottom Hem = 11.5+ (11.5*15%)
= 11.5+1.72=13.22/60 = 0.22

24. Thread Trimming = 10.5+ (10.5*15%)
= 10.5+1.57= 12.07 /60 = 0.20

25. Care label make = 22+ (22*15%)
= 22+ 3.3 = 25.3/60 = 0.42

26. Care label attach = 11.5+ (11.5*15%)
= 11.5+1.72=13.22/60 = 0.22

27. Thread trimming and Sticker Remove = 13.3+(13.3*15%)
= 13.3+1.99 = 15.29 / 60 = 0.25

Total SMV = 7.26

4.4 SMV Calculation (After line balancing)