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Six Sigma
”A way of working towards perfection » [16]
The Six Sigma is a financial improvement strategy for an organization and now a day it is being used in many industries. Basically it is a quality improving process of final product by reducing the defects; minimize the variation and improve capability in the manufacturing process. The objective of Six Sigma is to increase the profit margin, improve financial condition through minimizing the defects rate of product. It increases the customer satisfaction, retention and produces the best class product from the best process performance [ Pyzdek, Thomas. 2003]
In order to use the Six Sigma in an organization, there are many things that are needed to achieve the financial goals in the organization as below,
o Understand the needs and who are your customers, and what is product that you want to provide the customers
o Review of the data, consumer survey report, and feedback of customers and determine the product standard that we provide and quality service.
o Find out what are the defects are occurring and why these are produce during the manufacturing of process and how to reduce these problems by the different method.
o After implementation of different improvement actions, set up good matrices and follow up these actions and become the new standard of operating process [17].
Six Sigma Improvement Approach
The main thing of Six Sigma is to taking the existing product, process and improves them in a better way. It is a very powerful approach to achieve the financial goals for the organization and improving the company’s value by the following;
Data driven
Project based
Disciplined and systematic
Customers focused (internal & external)
Success of every organization is dependent on, how to introduce and implement Six Sigma in the organization. For clear understanding, “Six Sigma Onion” is a best example for showing the process of implement Six Sigma in the organization [16].
Process Capability
Sigma value increases the process performance in a better way. Another way of measure the process capability and performance by the statistical measurements like Cp, Cpk, Pp and Ppk. The Six Sigma means a 3.4 % defects part per million or yield of 99.9997% (perfect parts). Following is the table of comparison of different Sigma values at different defects part per million and capability of process here [15].
DMAIC Methodology
The DMAIC is a basic component of Six Sigma methodology- a better way to improve work process by eliminating the defects rate in the final product. The DMAIC methodology has five phases Define, Measure, Analysis, Improvement and Control.
Define Phase
Goal: In this phase, define the purpose of project, scope and process background for both internal and external customers. There are a different tools which is used in define phase like SIPOC, Voice of Customer and Quality Function deployment [Pyzdek, Thomas. 2003].
Output:
• A clear understanding of process improvement and how is it measure by the implementation of different tools.
• High level of process is achieved.
• A lot of successful factors list show that what customer requirement is?
Measure Phase
Goal: In order to determine the root cause of defects, focusing the data gather from current process for improvement. There are different methods to analysis data by sampling, Gauge R&R and capability process.
Output:
• Problem statement focused in the process
• Pinpoint the problem location due to different analysis of data
• What the process is capable or not?
Analyze Phase
Goal: Identify the root causes of problems and confirm them from data analysis. There are different methods used for this phase are Regression Analysis, Design of Experiment and Process analysis.
Output: What is the best setting for the improvement of process and also highlight the significant in the process.
Improve Phase
Goal: Develop the solution of problems in the process by implementing the different tools like FMEA and Pilot Plan.
Output: Identification of planned actions that are implemented for improvement and should reduce the impact and also proposed solution for the problems.
Control Phase
Goal: Using data, evolution of solution of problems and future plan and also maintain the standing operating procedure.
Output:
• Analysis of data before and after
• Well monitored system
• Completed documentation of process results [Pyzdek, Thomas. 2003].
Theoretical project
Theoretical means concerned primarily with theories or hypothesis rather than practical consideration. It is preferred to select theoretical thesis due to experience in field of textile industries especially in spinning technology. In this thesis, it is focused in details of different departments which involve in the manufacturing of yarn but especially on quality of yarn product, corrective and preventive action and critical success factors which effects on quality and yield of product.
For better understanding of process and analysis of data of different departments for the improvement of process, DMAIC methodology is a best technique which is using for analyze the process by the using of different tools like X-Y matrix, FMEA etc. Improving quality and continuous improvement can be done by the implementation of six sigma methodology. It is not only used for improvement of quality rather it is also use as a business management strategy or improvement of financial condition of organization. It was introduced by Motorola in 1980 [19].
The objective of Six Sigma is to reduce the variation in the process and also defects of the final product. In order to reduce the defects it is focus on critical success factors and takes preventive action against any failures and also minimizes the mechanical faults by the proper training of maintenance team. Inspection is also very important factor for checking quality of product before going to customer. That’s why; it’s necessary to focus more work for removing the defects in the process and reduce the risk for any complaint of product (Tennant, Geoff 2001)
Philosophy of Six Sigma is that if any defect occurs then it is necessary to look the process and take action for the cause. Excellent processes will allow average people to consistently generate superior result. Advantage of this technique is that customer will be more satisfied and loyal. Other advantage is that it improves efficiency and effectiveness of process and also financial saving is achieved in this way. It is learned by experience that for the improvement of any process there is need of training of staff from all area like from research and development, quality and production.
Reliability and validity
Reliability can be defined as” Measure of how stable, dependable, trustworthy and consistent a test in measuring the same thing each time. It can also be defined as “The degree of consistency between two measures of the same things” (Mehrens and Lehman, 1987) [20]
Validity can be defined as” the degree to which they accomplish the purpose for which they are being used” (Worthen et al., 1993)
In this thesis it is explained everything regarding to quality and reduce the defect rate. This thesis is reliable in yarn production because it is explained all those factors which may influence for the betterment of quality. It is also focused on better testing of raw material, as if raw material will be good then it will have positive aspect on our yield. So because of these characteristics our thesis is reliable as it fulfills all basic needs.
Validity of thesis is depending upon number of factors, like time, advancement in technology, overall economic environment, attitude and behavior of customer, supply and demand situation.
Historical Experience
Due to background experience in Yarn manufacturing process, it is decided to choose the thesis related to field “how to minimize the defects rate in different departments and final yarn by the DMAIC tool. During this job it was focused in all three departments such as Quality, Maintenance and Production. I followed all the standards which play important role for the satisfaction of the customer needs and expectations. Maintenance play important role in every field. It play very important role regarding to quality. Because of proper maintenance, quality of product will be better. So it was focus on maintenance department as well. This theoretical thesis is based upon our practical knowledge.
Blow room
Blow room is the initial step for yarn manufacturing process in spinning mill. In blow room cotton bales are opened and cotton is transfer from different number of machines with the help of air flow. This chapter clears the main objectives of blow room such as opening, cleaning and mixing and also describes the technical point regarding to quality point of view. Here also describes the defects which affect the yarn quality and preventive action to cover these defects according to quality standard. There is lot of things in this department which is described bellow;
Objective
Following are the basic operation or objectives of blow room
Opening
Cleaning
Mixing or blending
Micro dust removal
To extract the contamination in the cotton such as leaf, stone, iron particles, jute, poly propylene, colored fibers, feather and other foreign material from cotton by opening and beating.
To uniform feeding to the next stage such as carding machine
Recycling the waste material [5].
Technical points in Blow room
Following are the technical points in the blow room
Opening in blow room means opening the cotton in small pieces. The operation of opening means to increase volume of flocks while the number of fiber in the flock remains constant. That is the specific density of material is reduced.
If the size of dirt particle is larger, it can be removed easily.
A lot of impurities and contamination are eliminated at the start of the process.
As much opening of cotton will be more, cleaning result will be more acceptable. But this cleaning of cotton is done on the basis of high fiber loss. High roller speed gives more better cleaning effect but also more stress on fiber. So roller speed is adjusted at a nominal speed so there should be well opening of cotton and it does not effect of quality of fiber [5].
Cleaning efficiency of cotton is depending upon trash percentage. The cleaning efficiency is different for different verities of cotton with same trash percentage
If the opening of cotton is done well in initial stage then cleaning becomes easier. As surface area of opened cotton is more, so therefore cleaning is more efficient.
In traditional method more number of machine are used to open and clean natural fiber
If automatic bale opener machine is used, the tuft size of material should be as small as possible. In this way more efficiency of machine is achieved and machine stopping time is reduced.
For the opening of cotton, use inclined spiked lattice (tray) at the initial stage always a better way of opening of cotton with minimum damage.
Mechanical action on fibers creates some problems in the quality of yarn in the form of neps.
In beating operation by using a much shorter machine sequence, fibers with better elastic properties. In this way spin ability can be produced.
Stickiness in the cotton affects the process very badly in the way of production and quality.
It is necessary to control the temperature inside the department, when use stickiness cotton.
Released of dust particles into the air occurs whenever the raw material is rolled beaten or thrown about. Accordingly the air at such position is sucked away. For the removal of dust perforated drums, stationary drums are used.
Table of contents :
Chapter 1 Introduction
1.1 Process Introduction
1.2 Problem formulation
1.2 Brief Introduction of Departments
1.2.1 Blow room Process:
1.2.2 Carding Process
1.2.3 Drawing frame Process
1.2.4 Combing process
1.2.5 Roving frame
1.2.6 Ring Spinning Process
1.2.7 Winding Section
2.1 Six Sigma
2.2 Six Sigma Improvement Approach
2.3 Process Capability
2.4 DMAIC Methodology
2.4.1 Define Phase
2.4.2 Measure Phase
2.4.3 Analyze Phase
2.4.4 Improve Phase
2.4.5 Control Phase
3.1 Theoretical project
3.2 Reliability and validity
3.3 Historical Experience
4.1Blow room
4.1.1 Objective
4.1.2 Technical points in Blow room
4.1.3 Factors affecting on opening, cleaning and fiber loss
4.1.4 Critical success factors for Blow room
4.1.5 Importance of yarn quality
4.1.6 Guide line for Achieving Yarn Quality
4.1.7 Defects and Causes
4.1.8 Preventive action
4.2 Carding Section
4.2.1 Objective of Carding
4.2.1 Technical points in Carding
4.2.2 Feed the material in the form of lap
4.2.3 Flock feeding
4.2.4 Importance Points for Quality of Yarn
4.2.5 Critical Success Factors
4.2.6 Defects in Carding and Causes
4.3 Draw frame section
4.3.1 Objective
4.3.2 How Much Importance for Quality?
4.3.3 Causes of draw frame sliver variation
4.3.4 Preventive action of Frame sliver variation
4.4 Combing section
4.4.1 Objective
4.4.2 Importance of combing process by quality point of view
4.4.3 Critical success factors
4.4.4 Defects and causes in combing
4.5 Roving frame section
4.5.1 Objectives
4.5.2 Drafting
4.5.3 Twisting
4.5.4 Winding
4.5.5 How Much Important for Quality?
4.5.6 Critical Factors Affecting Roving Strength
4.5.7 Defects and causes in roving
4.6 Ring Spinning Section
4.6.1 Function of Ring Process
4.6.2 Ring Spinning Effects on Quality
4.6.3 Problems in Ring Process
4.6.4 Critical Success Factors
4.7 Winding process
4.7.1 Objectives of winding
4.7.2 How Much Importance for Quality?
4.7.3 Yarn faults and clearing
4.7.4 Yarn clearing concept of Uster Quantum clearer
4.8 Implementation of DMAIC tool in Winding Department
4.8.1 Justification for the selection of winding section
4.8.2 Understanding of winding process
4.8.3 Define Phase
4.8.3.1 Rate of Rejection of Departments
4.8.3.2 SIPOC Diagram
4.8.3.3 Winding Defects
4.8.4 Measure Phase
4.8.4.1 Cause & Effect Analysis
4.8.4.2 Data Collection
4.8.4.3 Measurement System Analysis
4.8.4.4 MSA for Defective Yarn cones
4.8.4.5 Conclusion
4.8.5 Analysis Phase
4.8.5.1 Effect of over hauling, product change and shift on Stitch defect
4.8.5.2 Effect of Yarn type on defect Stitch
4.8.5.3 Conclusion
4.8.6 Improve Phase
4.8.6.1 Parameters
4.8.6.2 Conclusion
4.8.7 Control Phase
4.8.7.1 SPC
4.8.7.2 Design the speed limits
4.8.7.3 Inspection procedure
4.7.7.4 MSA after inspector training
7 References
