quality control circle concepts and its tools

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FEATURES OF QUALITY CIRCLE The organization gets the total man Humanize the work i.e. Quality of work life is stressed and improved Brings out extra-ordinary qualities from ordinary people To display the human capabilities fully and eventually draw out infinite possibilities Prepares the employer and employees to meet the challenges of the changing time and conditions

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By: mittal.gajjar (102 month(s) ago)

ufffff its 2 long.. bt good..

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Quality Control Circle and its concepts with seven tools : 

Quality Control Circle and its concepts with seven tools Prepared by M.Ganesh Murugan 9715447621

Quality circle : 

Quality circle

Quality circle : 

Quality circle The QC circle was formally organized in Japan in 1962 by Japanese Union of Scientists and Engineers (JUSE) and the man who initiated the idea is Dr.Kaoru Ishikawa

FEATURES OF QUALITY CIRCLE : 

FEATURES OF QUALITY CIRCLE The organization gets the total man Humanize the work i.e. Quality of work life is stressed and improved Brings out extra-ordinary qualities from ordinary people To display the human capabilities fully and eventually draw out infinite possibilities Prepares the employer and employees to meet the challenges of the changing time and conditions

OBJECTIVES OF QUALITY CIRCLE : 

OBJECTIVES OF QUALITY CIRCLE Ensure harmony Effective team work Job satisfaction Problem solving capacity Communication Self development Leadership development Safety awareness and housekeeping Productivity Team building Participation Self-discipline

Remember : 

Remember Not just for only quality problems Not a forum for grievances Not a spring-board for demands Not a tool for management to unload problems Not problem-focussed, but performance-oriented Not for changing the existing organisational structure or chain of command Not a “cure all” or “sure cure” technique Not a panacea for all ills

Why? : 

Why? One of the prime objectives of QC is to improve the quality of work life and environment The survival and prosperity of any enterprise depends on the bottom line of the balance sheet i.E. Net profit/economic viability and stability. A higher level of quality will result in satisfied customer, repeat business, which in turn will improve the profitability, job security and overall harmony of enterprise. Hence, the emphasis on “quality”

Quality Circle differs from other Concepts - How ? : 

Quality Circle differs from other Concepts - How ? Everybody participates and contributes in the process of decision-making Problems are chosen, not given Decision by consensus, not by majority Performance-oriented, not problem-oriented Bottom-up approach Management-blessed, not management-directed Members are responsible from the identification of a problem to implementation of the solution i.E. For total performance Aims at the quality of work life Does not replace or substitute any of the systems or structure

QC Operation Cycle : 

QC Operation Cycle Problem identification emanates from The members of the circle Management Staff or technical experts Several problems are identified and the selection of the problem is the prerogative of the circle Problem analysis and discuss alternatives Data from specialist, if necessary Arrive at best solution Circle members discuss various alternatives also before reaching the best solution

QC Operation Cycle : 

QC Operation Cycle Management presentation The circle makes its recommendations directly to its in-charge using a powerful communication Review of recommendations and approval by management Thoroughly in consultation and coordination with peripheral departments and approves or disapproves Implementation Approved recommendations are implemented. Recommendations that are not approved are Communicated to the circle members. It is imperative to explain the reasons to the members of the circle for not approving their recommendations. Communication should be effective in either case

Identification of problems : 

Identification of problems From the familiarity of the members as well as leaders with the operation in which they are involved In day-to-day work From the proposals or suggestions by clients From the suggestions by the HOD’s From the suggestions or proposals by any employee in the organisation From the objectives set out in the company’s annual plan/target However, it is the prerogative of the circle to select the problem although the suggestions can emanate from various sources

approach problems : 

approach problems Positive attitude Frank discussions and brainstorming with everyone participating in a cooperative manner

solving the problem : 

solving the problem QC should exercise a systematic approach Confirms the existence of the problem Understands the nature of the problem Identifies the symptoms Finds out the causes Prepares a systematic programs for study Checks those programs with the other members Delegates assignment to members Seeks advice and assistance if required from outside agencies

solving the problem : 

solving the problem Finds out the various possibilities Uses the relevant techniques that are learnt for problem-solving Prepares a report of its proposal once it arrives at a solution Evaluates the relevance and practicability of the solution Recommends the solution Implements the solution

factors for successful functioning of qc : 

factors for successful functioning of qc 1.Meeting A QC meeting must be the focal point of all activities The meeting time should be such that it is convenient and acceptable for all members 2.Subject (themes) The subject chosen should be in consonance with the policies of management A subject which is familiar and of common concern to all the members of the circle should be handled first Only work related problem should be chosen A problem whose solution is within the capability of the members of QC should be selected The subject should be so chosen for the impact of its solution As a rule, a problem should be selected which can be solved within reasonable period of time

factors for successful functioning of qc : 

factors for successful functioning of qc 3.Managing the activities Give opportunities for simple and brief presentation for those members who are not used to speaking Before others Familiarize all the members with the environment gradually Utilize every opportunity of praise Suggest better ways of doing things after appreciating their efforts What is salt to food is humor to effective discussion without tension. A sense of humor is a necessary ingredient but strict discipline should prevail Circle members should display their respective role by earmarking their responsibility Use simple techniques effectively and thoroughly

factors for successful functioning of qc : 

factors for successful functioning of qc A problem must be selected and solved only if the members can assure themselves that it will not reoccur People must be sufficiently motivated even to the point of becoming greedy in getting the most out of activities

factors for successful functioning of qc : 

factors for successful functioning of qc 4.Education of QC members QC members must make it a habit to study Read text books as many times as possible and make the best use of them Develop the habit of getting as much data as possible from as many sources as possible and utilize them to the maximum extent Knowledge is not sufficient, but the application of knowledge is more important What is digestion to food is contemplation to knowledge. Hence applying the knowledge that is acquired in solving the problem is key to the success of circle Apply the techniques in such a simple manner that everyone can understand

factors for successful functioning of qc : 

factors for successful functioning of qc 5.Key factors for the success of QC activities Make a master plan and divide into elements Study, discuss and solve the problem with the co-operation of all the members so that their commitment is assured for the implementation Constantly review the progress and the status of the solution

factors for successful functioning of qc : 

factors for successful functioning of qc 6.How is a QC program organized? A qc program is an integrated system made up of several components – The members The leader The facilitator The executive committee The facilitator takes direction from the executive committee and co-ordinates the activities of the circle meeting and the leader conducts the meeting in such a way that the members of the circle participate

factors for successful functioning of qc : 

7.How to ensure longevity of QC activities? The following essential ingredients are imperative 7.1.To be problem conscious The leader, who is normally the group head/shift head should understand the role and function of Leading the sub-ordinates. They should continuously and constantly learn about the technique. Support from top and middle management is essential to make qc self-motivating Peripheral departments also must give their blessings for the continued effort of QC activities. Participation by everyone should not only be encouraged but ensured factors for successful functioning of qc

factors for successful functioning of qc : 

7.2.To enhance people’s awareness in 3 areas Quality (quality of entire working life) Problem Improvement People must be quality conscious in order to promote QC activities. Once people become problem conscious, improvement is bound to follow factors for successful functioning of qc

factors for successful functioning of qc : 

7.3.Ensuring voluntary participation People get real satisfaction when they are totally committed to think and act on their own For the overall prosperity. If one understands why the activities should be carried out voluntarily, the commitment is bound to follow factors for successful functioning of qc

factors for successful functioning of qc : 

7.4.To find pleasure and sense of satisfaction in the QC activities There are ten kinds of happiness in QC activities Happiness of developing self-confidence Happiness of being recognized for one’s activities Happiness of displaying one’s ability and capability Happiness of acquiring the ability to identify one’s capability Happiness to develop and enrich one’s potential ability Happiness to be able to recognize one’s potential ability Happiness to understand and co-operate with the members of the circle Happiness to have friends and affectionate sub-ordinates factors for successful functioning of qc

factors for successful functioning of qc : 

Happiness to belong to a company where the QC activities are encouraged and promoted Happiness of gaining indirect material reward through the prosperity and growth of the company factors for successful functioning of qc

factors for successful functioning of qc : 

7.5.Training Training and re-training from the top management to the circle member is an indispensable and inevitable part of ensuring longevity of circles The members must also be taught value engineering, job instruction, job method, job relations, creativity development and leadership qualities factors for successful functioning of qc

factors for successful functioning of qc : 

7.6.How often the circle meetings are held? As a rule of the thumb, circle meetings are held once in a week However, some companies have introduced variations It is desirable to reduce the duration and increase the frequency of the meeting. factors for successful functioning of qc Format enclosed

factors for successful functioning of qc : 

factors for successful functioning of qc Format enclosed

Structure of qc : 

The QC circle is program is an integrated system consisting of the following Steering committee Divisional review committee Coordinators and facilitators Circle leader Circle members Structure of qc

Structure of qc : 

Steering committee This committee comprises of the executive director, general managers and a member secretary (nominated by management). This committee sets goals and objectives for the QCC activities and establishes operational guidelines It meets as often as necessary but at least once a quarter to review the progress. The secretary is responsible for the overall coordination of QC circle activity in the company Structure of qc

Structure of qc : 

Divisional review committee This committee comprises of the divisional head, departmental heads, coordinators and facilitators(member secretary). It provides active support to the circles The committee meets as often as necessary but at least once a month to review the progress Structure of qc

Structure of qc : 

Coordinators Organizes training programs for members as and when new circles are formed Convenes the steering committee meeting regularly once in two to three months and maintains the minutes thereof. Organizes top management presentations regularly once in two to three months Centrally registers circles as and when formed and also maintains records of number of members, frequency of management representations, etc. Structure of qc

Structure of qc : 

Co-ordinates and evolves a consensus for norms to asses the performance of different quality circles and of different divisions Co-ordinates and ensures availability of common facilities to all quality circles Prepares a budget for the functioning of quality circles and submits the same to the steering committee for adoption Structure of qc

Structure of qc : 

Facilitators Is responsible for the successful operation of the quality circles in his area. He has to be a guide, counselor, teacher and a catalyst Ensures necessary facilities for quality circles to operate effectively lends assistance and support to the leader whenever required and also helps in the training of members Is invited to the meetings of the departmental or steering committees wherein he gives a resume of the activities of quality circles in his jurisdiction Structure of qc

Structure of qc : 

Circle leader/deputy leader Makes the necessary facilities available, with the help of facilitators and others, for enabling quality circles to perform without constraints Assigns tasks to different member from time to time to maintain a high degree of individual involvement and participation Trains the members in various problem-solving techniques and other facets of quality circle operations, and gives them necessary guidance whenever required, with the help of the facilitator and others, if necessary Structure of qc

Structure of qc : 

Maintains a high degree of cohesiveness of his team. He does not act as a boss in quality circle activities but as a friend and partner so that conflicts are avoided and group cohesiveness is maintained all the time Ensures that every circle member is involved in circle activity and a high level of enthusiasm and involvement is maintained Plans the agenda of meetings carefully and conduct meetings regularly and effectively Ensures discipline and decorum during the meetings Structure of qc

Structure of qc : 

Chalks out action plans for a progressive solution of problems through data collection, interaction and sets time bound programs for implementation of the circle’s recommendations Encourages and evolves consensus decision-making processes so that win-lose situations are obviated Ensures that record-notes of meetings and progress of problems are maintained in two separate registers regularly and effectively Interfaces with other levels of management, the facilitator and different functional agencies to ensure the effective working of his quality circle Structure of qc

Structure of qc : 

Takes necessary steps continuously in conjunction with other members, facilitators, executives and the department head to ensure that his quality circle maintains a high degree of morale and enthusiasm continuously and thereby catalyses the quality circle movement in the organization to grow steadily and healthily Organizes presentations to departmental head and top management at least once in two to three months Feeds the information relating to the highlights of his circle activities to the agency concerned for publication in appropriate newsletters and journals Structure of qc

Structure of qc : 

Circle members Participate actively in the discussions during the meeting and all other activities of the circle. They willingly execute specific assignments that may be given to them as decided in the circle meetings. Thus they actively assist leader/deputy leader in effectively and efficiently conducting the circle activities Contribute towards building of a cohesive group through which they try to achieve the highest standards of performance Structure of qc

Structure of qc : 

Take part in management presentation Through their personal conduct and enthusiasm, help in propagating the quality circles concept in other areas where circles are yet to be launched Assimilate the inputs given to them during training and develop in themselves the capability for systematically identifying analyzing and resolving problems and also attain leadership qualities Structure of qc

Basic Seven Tools of quality Control : 

Check sheet Stratification Pareto chart Cause and effect diagram Histogram Scatter diagram Graph and control chart Basic Seven Tools of quality Control

Seven Tools ? : 

A scientific approach of solving problems and making workplace improvements Helps individuals/teams of diagnose, solve and prevent problems Can be used to solve 90% of workplace problems Simple yet powerful histogram Seven Tools ?

Check sheet : 

Check sheet is a systematic method of collecting, recording and presenting the relevant data in a simple manner Helps individuals/teams of diagnose, solve and prevent problems Rationale and Benefits To make data gathering simple, systematic, easy and effective To arrange and present data in such a way that it can be understood and used easily Enables “management by facts” as opposed to “management by opinion” Check sheet

Types of Check sheet : 

Process performance check sheet Defect item check sheet Defect location check sheet Defect cause check sheet Task conformation check sheet Types of Check sheet

Steps in making a Check sheet : 

Establish what information is needed Establish “operational definition” for the data to be collected Determine 5W and 2H of check sheet Construct the check sheet Test the check sheet Use the check sheet Use the information (remember three rules of QC) Steps in making a Check sheet

5W 2H for Check sheet : 

Why is the data needed? What type of check sheet should be used? Where should the data should be collected from? (Plant/machine/place) Who has to collect the data? (Operator/ supervisor/manager) When will the data be collected? (Every hour/ at the time of receipt) How should the data should be measured? (Instrument/clock) How much data is essential? 5W 2H for Check sheet

Construction of Check sheet : 

Check sheet should broadly have three types of information Title of the check sheet Source information Name of the project/ problem theme Location of data collection Date and/or time Name of the person recording data Content information Column with defect/event name Column to record frequency Column to record total Construction of Check sheet

Test the Check sheet : 

Test the check sheet with at least three different collectors Check if the operational definition is really “operational” Reconfirm that the columns are relevant and required Check if the check sheet is easy to record and use Make changes based on the feedback Test the Check sheet

Use the Check sheet : 

Explain the check sheet to the data collector Ensure that the data collector understands the reason for which the data is being collected Collect data Standardize its use to assure consistency Tally mark = 5 Use the Check sheet

Use the Information : 

Pay particular attention to irregular data and irregular conditions Use data from the check sheet for further analysis - Pareto chart, histogram, scatter diagram Ensure that all the data that is recorded is put to use OR is likely to be put in future Regularly audit the use and the usefulness of check sheet Use the Information

Process Performance Check sheet : 

Process Performance Check sheet

Defective Item Check sheet : 

Defective Item Check sheet

Defect Location Check sheet : 

Defect Location Check sheet

Defect Cause Check sheet : 

Defect Cause Check sheet

Task confirmation Check sheet : 

Task confirmation Check sheet

Possible problems with Check sheet : 

Possible problems with Check sheet Goals are too vague No agreed operational definition Data is not collected on time Too much time and effort being spent on recording in the check sheet Check sheet is too complex Different people are using different check sheet for the same issue

Check Sheet-Weekly : 

Check Sheet-Weekly

HyperLink : 

HyperLink check-sheet-histogram.xls

Example : 

Example

Stratification : 

Stratification A technique used to divide the data into sub-categories or classification to provide useful insight into the problem Root word is “strata” which means Group Division Sub-class Levels Layers Stratification is an act of dividing the data based on groups, division, sub-class, causes etc.

Rationale and Benefits : 

Rationale and Benefits Data comes from different sources. e.g: different machines, instruments, cities, operators etc. Data sometimes masks real information. Stratification helps in getting meaningful information from data. Divide the data and conquer the information

Steps in Stratification : 

Steps in Stratification List all conditions Collect and stratify data Interpret the data

1.List all conditions : 

1.List all conditions Shift Location Operator Product Machine Inspection equipment Raw material source Day of week Time of the day Material batch Inspector Production batch List all conditions that may seem to be cause of the problem

2.Collect and Stratify Data : 

2.Collect and Stratify Data Collect additional data based on classification, if necessary Stratify data based on the classification

3.Interpret the data : 

3.Interpret the data Calculate average of each classification or plot appropriate graph Look for significant differences or abnormalities in data Generate a list of possible causes

Example: Rejection of Components : 

Example: Rejection of Components Un – stratified data

Example: Rejection of Components : 

Example: Rejection of Components Stratified data

Pareto Chart : 

Pareto Chart Pareto chart is a diagram that shows the order of the largest number of occurrences by item or by classes, and the cumulative sum total

beginning of Pareto Chart : 

beginning of Pareto Chart Vilfredo Pareto (1848-1923), an Italian economist discovered in 1897 that 80% of a nation’s wealth was owned by 20% of the population Dr. Joseph.M.Juran applied this principle to quality management and called it the pareto principle

Rationale and Benefits : 

Rationale and Benefits Pareto principle: 80% of the problems come from 20% of the causes Distinguishes between vital few and trivial many Displays relative importance of causes of problem Helps the team to focus on those causes that will have the greatest impact when solved

Pareto Principle : 

Pareto Principle

Steps in Making a Pareto Chart : 

Steps in Making a Pareto Chart Select the problem Collect data Sort data & calculate cumulative frequency Draw the axes Construct the bars Draw the cumulative percentage line Title and label the chart Identify vital few from the trivial many and plan further action

1.Select the problem : 

1.Select the problem Select the problem for investigation Decide what data will be necessary and how to classify them Determine the method of collecting data and period of data collection Design a separate check sheet if necessary E.g: causes for service complaints of computer system

2.Collect data : 

2.Collect data

3.Sort data and calculate cumulative percentage : 

3.Sort data and calculate cumulative percentage

4.Construct the axes : 

4.Construct the axes

5.Draw the Bars : 

5.Draw the Bars

6.Draw the Cumulative Percentage line : 

6.Draw the Cumulative Percentage line

7.Label and Title the Chart : 

7.Label and Title the Chart

8.Interpret the Chart : 

8.Interpret the Chart

Tips for Making Good Pareto : 

Tips for Making Good Pareto It is undesirable that “others” represent high percentage (should be < 10%) If the cause of a problem can be solved easily, implement it even if it belongs to trivial many Wherever possible, compare monetary data with frequency data Draw the Pareto chart before and after improvement

Cause and Effect Diagram : 

Cause and Effect Diagram A diagram which represents meaningful relationship between an effect and its causes A diagram which shows the relation between a quality characteristic and the cause factor

Rationale and Benefits : 

Rationale and Benefits Enables a team to identify, explore and graphically display all the possible causes related to a problem A cause and effect diagram is good for seeing the whole “causal” relationship Enables identification of root causes and not symptoms

Father : 

Father Dr. Kaoru Ishikawa developed the first cause and effect diagram in 1943 while consulting for Kawasaki steel works Dr.Joseph.M.Juran named it as Ishikawa diagram

Structure of C & E Diagram : 

Structure of C & E Diagram

Three types of Cause and Effect Diagram : 

Three types of Cause and Effect Diagram Dispersion Analysis Type. Process Flow Classification Type. Cause – Enumeration Type. Note Dispersion analysis type and Cause – Enumeration type differ only in the method of construction

Dispersion Analysis Type : 

Dispersion Analysis Type

Process Flow Classification Type : 

Process Flow Classification Type

Steps in Constructing Dispersion Type C & E Diagram : 

Steps in Constructing Dispersion Type C & E Diagram State the undesirable effect Identify the main cause groups Identify causes and sub-causes Identify potential root causes

1.State the undesirable effect : 

1.State the undesirable effect Draw the back Bone and draw a line High Rejection Causes Effect

2.Identify the main cause groups : 

2.Identify the main cause groups Such as man, machine, method, material, measurement, tool High Rejection Causes Effect Man Method Machine Material Measurement Environment

3.Identify the causes and sub-causes : 

3.Identify the causes and sub-causes Brainstorm: Ask “why” questions Causes Effect Man Method Machine Material Rod bent Poor handling No Inspection High Hardness Measurement Environment High Rejection

4.Identify the root causes : 

4.Identify the root causes Runs out of ideas, focus attention to place Causes Effect Man Method Machine Material Rod bent Poor handling No Inspection High Hardness Measurement Environment High Rejection

Example : 

Example Note: that some ideas appear in two different places. “Calibration” shows up under “methods” as a factor in the analytical procedure, and also under “measurement” as a cause of lab error. “Iron tools” can be considered a “methods” problem when taking samples or a “manpower” problem with maintenance personnel.

Steps in Constructing Process Flow Type c & E Diagram : 

Steps in Constructing Process Flow Type c & E Diagram State the undesirable effect Identify the main process flow diagram Identify the causes and sub – causes at each stage of the process Identify the potential root cause(s)

1.State the undesirable effect : 

1.State the undesirable effect Draw a vertical line state the undesirable effect

2.Draw the main process flow : 

2.Draw the main process flow Draw a vertical line state the undesirable effect

3.Identify the causes and sub-causes at each stage of the process : 

3.Identify the causes and sub-causes at each stage of the process

4.Identify potential root cause(s) : 

4.Identify potential root cause(s)

Steps in Constructing Cause Enumeration Type C & E Diagram : 

Steps in Constructing Cause Enumeration Type C & E Diagram State the undesirable effect List all possible causes using brainstorming Arrange causes and sub – causes showing the relationship between cause and effect Identify potential root cause(s)

1.State the undesirable effect : 

1.State the undesirable effect

2.List all the possible causes : 

2.List all the possible causes

3.Arrange causes and sub-causes suitably : 

3.Arrange causes and sub-causes suitably

4.Identify potential root causes : 

4.Identify potential root causes

Hints for constructing C&E Diagram : 

Hints for constructing C&E Diagram Identify all the relevant causes (factors) & the causes most strongly influencing the effect (characteristic) Express the effect (characteristic) “negatively” The linking question between effect and its cause is “why?” Make the same number of causes and effect diagrams as that of effects

Control chart : 

Control chart It is a type of run chart used for studying the process performance over time in order to understand and reduce variation

Father of Control Chart : 

Father of Control Chart Dr.Walter.A.Shewart invented the control chart He was working in bell labs on a project to make all telephones alike Published the book called “Economic control of quality of manufactured product” in 1931

Principles of variation : 

Principles of variation Every process is subject to variation More the variation in the process, more the loss to the society Two types of causes affect variation Common cause (also known as chronic cause, chance cause) The cumulative effect of many small and “individually uncontrollable” causes of variation in a process. Express the effect (characteristic) “negatively”

Principles of variation : 

Principles of variation Special cause (also known as sporadic or assignable cause) One of a few causes of variation that result in a large variation in the process Action on variation entirely depends on type of cause identified

Rationale and Benefits : 

Rationale and Benefits Control chart is used for differentiating between common causes and special causes of variation Control charts also helps in determining whether the Process is stable Process is capable It helps in predicting process performance

Types of data : 

Types of data Variable data Data that can be measured E.g. Weight, height, length, hardness, diameter, angle Attribute data Data that can be counted E.g. Defects, scratches, dent, spatters, blow, holes, cracks

Classification of control chart : 

Classification of control chart

Classification of control chart : 

Classification of control chart

Parts of Control Chart : 

Parts of Control Chart

Definition of terms : 

Definition of terms Sub groups Smaller groups of sample data collected over time Central line The average of all the sub group averages Control limits The outer limits of “Process Variation”

Definition of terms : 

Definition of terms

Steps in constructing Control chart : 

Steps in constructing Control chart Collect the data Calculate sub – group average Calculate overall average Calculate the range Compute average of range Calculate control limit for X and R Plot the chart Interpret the chart

1.Collect data : 

1.Collect data Collect and stratify data into sub groups

2. Calculate sub group average : 

2. Calculate sub group average 1 = X1+X2+X3+X4+X5 n 1 = 47+32+44+35+20 5 = 35.6 Where n is the size of the groups

3.Calculate the overall average : 

3.Calculate the overall average = 35.6+29.2+22.2+39.2 4 = 35.6 Where K is the size of the sub group = 1+ 2+ 3+ 4 K

4.Calculate the subgroup Range : 

4.Calculate the subgroup Range = Maximum value – Minimum value = 47 – 20 = 27 R R1

5.Calculate the Average Range : 

5.Calculate the Average Range = 1 + 2 + 3 + 4 K = 27 + 18 + 33 + 31 4 R R R R R R Where K is the size of the sub group

6.Compute Control limits for x chart : 

6.Compute Control limits for x chart Central line = Upper control limit : UCL = + A2 Lower control limit : LCL = - A2 A2 is the coefficient whose value depends on the subgroup size R R

6.Compute Control limits for R Chart : 

R 6.Compute Control limits for R Chart Central line = Upper control limit : UCL = D4 Lower control limit : LCL = D3 D3 and D4 are the coefficient whose value depends on the subgroup size R R

6.Compute Control limits for R Chart Coefficients for - R chart : 

6.Compute Control limits for R Chart Coefficients for - R chart

7.Plot the Control Chart : 

Vertical axis : and R values Horizontal axis : sub – group number Draw the central line : and R Draw the control limits Plot the and R values and join the points Write necessary items like name of the process, product, size of the subgroup, work conditions, shift, etc. 7.Plot the Control Chart

8.Interpret the Chart : 

8.Interpret the Chart

Stable Process : 

Stable Process Random variation and no systematic pattern No action required (if Cpk > 1.67)

Rule 1: Points beyond control limit : 

Rule 1: Points beyond control limit Presence of special cause Identify root cause and take action

Rule 2: Run of 7 Points on one side of central line : 

Rule 2: Run of 7 Points on one side of central line Presence of special cause Process has shifted

Rule 3: Six consecutive Points Increasing or Decreasing : 

Rule 3: Six consecutive Points Increasing or Decreasing Presence of special cause Process is deteriorating

Rule 4 : Periodicity : 

Rule 4 : Periodicity Presence of special cause Periodic Interference in the process

Rule 5: Fourteen consecutive points alternating up & down : 

Rule 5: Fourteen consecutive points alternating up & down Presence of special cause Identify root cause and take action

Process Capability : 

Process Capability Process capability is a measure of inherent variability of the process when compared with the customer requirements

Rationale and Benefits : 

Rationale and Benefits Assess capability of a process to meet customer’s requirement Assist in selecting or modifying a process Assist in selection of machine To build quality into the product and process rather than achieving quality by inspection

Process Capability Assessment : 

Process Capability Assessment Establish process variation process variation = 6σ σ = . d2 d2 is a constant based on sub – group size Refer slide number 124 R

Compare with customer specification : 

Compare with customer specification Capability = Customer Requirement Process variation Cp = USL –LSL 6 σ Cp > 1.33; Process is more capable than customer requirement Cp = 1.0; Process is just capable of meeting customer’s requirement Cp < 1.0; Process is not capable of meeting customer’s requirement

Compare with customer specification : 

Compare with customer specification Cpk = Minimum (USL - ) ; ( - LSL) 3σ 3σ Cpk = Cp; process is centered with respect to customer’s requirement Cpk љ Cp; Process is not centered with respect to customer’s requirement

Histogram : 

Histogram Histogram is a type of bar chart representing the frequency distribution of the data from a process

Rationale and Benefits : 

Rationale and Benefits Displays large amount of data, that are difficult to interpret in tabular & graphical form Shows the relative frequency of occurrence of the various data values Provides useful information for understanding the present performance and predict future performance of the process

Rationale and Benefits : 

Rationale and Benefits Reveals the centering, variation & shape of the data Helps evaluate process capability & the question “is the process capable of meeting customers requirements?” Enables corrective action to keep the process within specification limits Excellent planning and forecasting tool

When to Use a Histogram : 

When to Use a Histogram When the data are numerical When you want to see the shape of the data’s distribution, especially when determining whether the output of a process is distributed approximately normally When analyzing whether a process can meet the customer’s requirements When analyzing what the output from a supplier’s process looks like

When to Use a Histogram : 

When to Use a Histogram When seeing whether a process change has occurred from one time period to another When determining whether the outputs of two or more processes are different When you wish to communicate the distribution of data quickly and easily to others

Example : 

Example

Steps in construction of Histogram : 

Steps in construction of Histogram Decide on the process measure Gather data Prepare of frequency table Calculate range, class intervals, class width and boundaries Draw the axes Draw the bars Interpret the histogram

1.Decide on the process measure : 

1.Decide on the process measure Only one parameter can be used for constructing the histogram The data should be variable data, i.e., Measured on a continuous scale (weight, time, temperature, dimensions, speed, etc.) Example : weight of a rice bag

2.Gather and Record data : 

2.Gather and Record data For accurate analysis of mean, dispersion and patterns, collect at least 50 to 100 data points

3.Prepare a frequency table from the data : 

3.Prepare a frequency table from the data Calculate the number of data points, n Determine the range, R Determine the number of class intervals, k Determine the class width, H Establish the class boundaries Establish class intervals Construct the frequency table

3.Prepare a frequency table from the data : 

3.Prepare a frequency table from the data Calculate the number of data points, n Count the number of data points “n” in the sample n = 64 data points

3.Prepare a frequency table from the data : 

3.Prepare a frequency table from the data Calculate the number of data points, n Determine the range, R Determine the range “R” in the sample. Range is the smallest value in the set of data subtracted from the largest value R = Xmax – Xmin R = 101.6 – 98.6 = 3.0

3.Prepare a frequency table from the data : 

3.Prepare a frequency table from the data Calculate the number of data points, n Determine the range, R Determine the number of class intervals, k Determine the number of class intervals, “k” needed. The following table can be used as a thumb rule k = 7 classes

3.Prepare a frequency table from the data : 

3.Prepare a frequency table from the data Calculate the number of data points, n Determine the range, R Determine the number of class intervals, k Determine the class width, H Determine the class width “H”. The formula for this is H = R/k This should be rounded off to a suitable value depending upon the data collected H = 3.0 / 7 H = 0.428 ~ 0.5

3.Prepare a frequency table from the data : 

3.Prepare a frequency table from the data Calculate the number of data points, n Determine the range, R Determine the number of class intervals, k Determine the class width, H Establish the class boundaries Use the smallest individual measurement in the sample or round off to the next appropriate lowest round number. This will be the lower end point for the first class interval Do the same for the highest number. This will be the higher end point for the last class interval Class Boundaries – 98.5 & 102.0

3.Prepare a frequency table from the data : 

3.Prepare a frequency table from the data Establish class intervals Add the class width “H” to the lower end point. This will be the lower end point for the next class interval Each class interval must be mutually exclusive Add the class width to the lower class boundary until the “K” class intervals and/or the range of all the numbers are obtained 98.50 – 98.99 100.00 – 100.49 99.00 – 99.49 100.50 – 100.99 99.50 – 99.99 101.00 – 101.49 101.50 – 101.99

3.Prepare a frequency table from the data : 

3.Prepare a frequency table from the data Construct the frequency table

4.Draw the Axes : 

4.Draw the Axes

5.Draw the Bars : 

5.Draw the Bars

Interpretation of the Histogram : 

Interpretation of the Histogram Process Centering Process Variation (Dispersion) Histogram Shape Process Comparison with specification(Process Capability)

Interpretation of the Histogram : 

Interpretation of the Histogram Process Centering

Interpretation of the Histogram : 

Interpretation of the Histogram Process Centering

Interpretation of the Histogram : 

Interpretation of the Histogram Process Centering

Interpretation of the Histogram : 

Interpretation of the Histogram Process Variation (Dispersion) Process too variable Process within requirements What is the variation or spread of the data? Is it too Variable?

Interpretation of the Histogram : 

Interpretation of the Histogram Histogram Shape Normal distribution Skewed distribution Distribution with isolated island Bi-modal distribution

Interpretation of the Histogram : 

Interpretation of the Histogram Process Comparison with specification(Process Capability) Process capable and centered Maintain Process Process capable but not centered Re-set to centre the Process

Interpretation of the Histogram : 

Interpretation of the Histogram Process Comparison with specification(Process Capability) Process just capable and centered Reduce variation to avoid defects Process just capable but not centered Centre process and reduce variations

Interpretation of the Histogram : 

Interpretation of the Histogram Process Comparison with specification(Process Capability) Process not capable but centered Reduce process variation to avoid defects

Check points for Histogram : 

Check points for Histogram Choose critical process parameters Gather as much as data as possible Choose appropriate class intervals, width, boundaries and scale Specify targets and specification limits Take corrective action and verify

Histogram Analysis : 

Histogram Analysis Before drawing any conclusions from your histogram, satisfy yourself that the process was operating normally during the time period being studied. If any unusual events affected the process during the time period of the histogram, your analysis of the histogram shape probably cannot be generalized to all time periods Analyze the meaning of your histogram’s shape

Scatter Diagram : 

Scatter Diagram A chart used to study and identify the possible relationship between two variables To identify the possible relationship between the changes observed in two variables To establish the Existence of correlation Type of correlation Strength of the relation

Rationale and Benefits : 

Rationale and Benefits To confirm a hypothesis (assumption) that two variables are related Provide both visual and statistical means to test the strength of a potential relationship Provide a good follow up to a cause and effect diagram to find out if there is more than just a consensus connection between causes and effects

Examples of two variables : 

Examples of two variables Cake height and Oven temperature Weight and Height of a man Population & Literacy levels in a state Weight error and Earthing voltage Nonconformance & Operator experience. Hardness and carbon content Inspection mistakes and Illumination levels Elongation of threads and moisture content Child’s height and Father’s height Quality characteristic and the factor affecting it

Example : 

Example Weight and Height of a Person

Steps in Making a Scatter Diagram : 

Steps in Making a Scatter Diagram Collect paired data Choose independent and dependent variable Draw the axes Plot the points Label and title the charts Interpret the chart

1.Collect Data : 

1.Collect Data Collect 50 – 100 paired data (X,Y) between which you want to study the relation, and construct a data chart

2.Choose Independent & Dependent Variable : 

2.Choose Independent & Dependent Variable Always choose ‘X’ axis for the cause and ‘Y’ axis for the effect, when the two variables consists of a factor and quality characteristics Oven temperature = independent Cake height = dependent Find the respective maximum and minimum values of the variables

3.Draw the axis : 

3.Draw the axis

4.Plot the data : 

4.Plot the data

6.Interpreting the Chart : 

6.Interpreting the Chart

6.Interpreting the Chart : 

6.Interpreting the Chart

6.Interpreting the Chart : 

6.Interpreting the Chart

6.Interpreting the Chart : 

6.Interpreting the Chart

6.Interpreting the Chart : 

6.Interpreting the Chart

Thank you : 

Thank you M.Ganesh Murugan 9715447621

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