Quality Assurance that relies primarily on inspection after production is referred to as acceptance sampling.
Quality assurance efforts that occur during production are referred to as statistical process control.
Approaches to Quality Assurance The least progressive The most progressive Inspection before/after production Corrective action during production Quality built into the process Acceptance Sampling Process Control Continuous Improvement
Monitoring in the production process can occur at three points: before production, during production and after production.
Inputs Transformation Outputs Acceptance Sampling Process Control Acceptance Sampling
How Much to Inspect and How Often
Low cost high volume items like paper clips, wooden pencils etc. often require little inspection because
The cost associated with passing defectives is quite low
The processes that produce these items are usually highly reliable
Conversely, high cost low volume items that have large costs associated with passing defectives often require more intensive inspections. E.g.. Space vehicle.
In high volume systems automated inspection is one option that can be employed.
Amount of Inspection Total Cost Cost of Inspection Cost of passing defectives Optimal Amount of inspection Cost 0
Where to inspect in the process
Raw materials and purchased parts
Before a costly operation
Before an irreversible process
Before a covering process
Examples of inspection points Appearance Shelf displays Quality, Quantity Deliveries Supermarket Completeness, productivity Maid service Appearance, Waiting time, accuracy of bills Main Desk Hotel/Motel Safe, well-lighted Parking Lot Accuracy Cashier Fast Food Characteristics Inspection points Type of business
Quality is the ability of a product or service to consistently meet or exceed customer expectations.
The Quality Gurus
“ Father of statistical quality control”
W. Edwards Deming
Joseph M. Juran
Philip B. Crosby
Key Contributors to Quality Management
Total Quality Management
Definition-Managing the entire organization so that it excels on all dimensions of products and services that are important to the customer.
Total = Quality involves everyone and all activities in the company Quality = Conformance to requirements Management = Quality can and must be managed
Ten Steps to TQM
Pursue new strategic thinking
Know your customers
Set true customer requirements
Concentrate on prevention not correction
Reduce chronic waste
Pursue a continuous improvement strategy
Use structured methodology for process improvement
Use balanced approach
Apply to all functions
Elements of TQM
Decisions based on facts
Knowledge of tools
Quality at the source
Principles of TQM
Quality can and must be managed
Everyone has a customer and is a supplier
Process not people are the problem
Every employee is responsible for quality
Problems must be prevented, not just fixed
Quality must be measured
Quality improvements must be continuous
The quality standard is defect free
Goals are based on requirements, not negotiated
Life cycle costs, not front end costs
Management must be involved and lead
Plan and organize for quality improvement
Company-wide definition of quality
Strategic plan for change
Real employee empowerment
Time to devote to quality initiatives
Obstacles to Implementing TQM
Poor inter-organizational communication
View of quality as a “quick fix”
Emphasis on short-term financial results
Internal political and “turf” wars
Obstacles to Implementing TQM
Design Quality- refers to the inherent value of the product in the market place and is thus a strategic decision for the firm.
E.g. performance, features, reliability, durability, response, aesthetics
Conformance Quality- refers to the degree to which the product or service design specifications are met. The activities involved in achieving the conformance are of a day to day nature.
Product with high design quality can have a low conformance quality or vice-versa.
The Consequences of Poor Quality
Loss of business
Substandard parts and materials
Ethics and Quality Having knowledge of this and failing to correct and report it in a timely manner is unethical.
Quality at the Source
The philosophy of making each worker responsible for the quality of his or her work.
i.e. the person who does the work takes responsibility for making sure that his or her output meets specifications.
Costs of Quality
Appraisal Costs- Cost to ensure that product is acceptable e.g. inspection, testing
Prevention Costs- The sum of all costs to prevent defects e.g. train, redesign, purchase new, make modifications
Internal Failure Costs- Costs for defects incurred within the system e.g. scrap, rework, repair
External Failure Costs- Costs for defects that pass through the system e.g. warranty replacements, loss of goodwill, product repair
Philosophy that seeks to make never-ending improvements to the process of converting inputs into outputs.
Kaizen: Japanese word for continuous improvement.
First introduced by US Defence services in the manufacture of aircrafts and aerospace vehicles in 1962- “ZD Program”
Creator is the Master- worker is more knowledgeable and suitable to identify & rectify errors
Inspection by Internal agency is better than external person- Inspection by outside agency may lead to presumption that workers have less knowledge & could affect their morale
Prevention is better than cure- Errors are caused by lack of knowledge and lack of attention. Improved by making workers directly involved in the manufacture and providing better training, better supervision and assistance. Workers are to be convinced that they are capable of producing products with zero error
Success of ZD depends on –
Top Management involvement and commitment
Selling the idea
Identify a critical process that needs improving
Identify an organization that excels in this process
Contact that organization
Analyze the data
Improve the critical process
Simple practices that prevent errors or provide feedback
in time for worker to correct errors.
e.g. defects, omitted processing, missing parts, wrong parts
It includes tooling that-
Prevents worker from making an error that leads to a defect before starting a process
Gives rapid feedback of abnormalities in the process to the worker in time to correct them.
Malcolm Balridge National Quality Award
The Deming Prize
The European Quality Award
Master Black Belt
Malcolm Balridge National Quality Award
1.0 Leadership (125 points)
2.0 Strategic Planning (85 points)
3.0 Customer and Market Focus (85 points)
4.0 Information and Analysis (85 points)
5.0 Human Resource Focus (85 points)
6.0 Process Management (85 points)
7.0 Business Results (450 points)
Benefits of Balridge Competition
Winners share their knowledge
The process motivates employees
The process provides a well-designed quality system
The process requires obtaining data
The process provides feedback
European Quality Award
Prizes intended to identify role models
Corporate social responsibility
People development and involvement
The Deming Prize
Honoring W. Edwards Deming
Japan’s highly coveted award
Main focus on statistical quality control
Set of international standards on quality management and quality assurance, critical to international business
A set of international standards for assessing a company’s environmental performance
ISO 9000 Quality Management Principles
A systems approach to management
Factual approach to decision making
Mutually beneficial supplier relationships
ISO 14000 - A set of international standards for assessing a company’s environmental performance
Standards in three major areas
Systems development and integration of environmental responsibilities into business planning
Consumption of natural resources and energy
Measuring, assessing and managing emissions, effluents, and other waste
Quality Awards were discussed in the class and assignment given
Statistical Quality Control
SQC- Techniques designed to evaluate quality from a conformance view. That is how well we are doing at meeting the specifications that have been set during the design of the parts or services that we are providing.
SPC- Techniques for testing a random sample of output from a process to determine whether a process is producing items within a prescribed range.
Normal Distribution Mean 95.44% 99.74% Standard deviation
Basic Quality Tools
Pareto Analysis 80% of the problems may be attributed to 20% of the causes. Smeared print Number of defects Off center Missing label Loose Other
Cause-and-Effect Diagram Effect Materials Methods Equipment People Environment Cause Cause Cause Cause Cause Cause Cause Cause Cause Cause Cause Cause
Purpose: to monitor process output to see if it is random
A time ordered plot representative sample statistics obtained from an on going process (e.g. sample means)
Upper and lower control limits define the range of acceptable variation
Control Limits Sampling distribution Process distribution Mean Lower control limit Upper control limit
Control Chart 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 UCL LCL Sample number Mean Out of control Normal variation due to chance Abnormal variation due to assignable sources Abnormal variation due to assignable sources
Quality Control Techniques For Variables For Attributes X Chart R Chart P Chart C Chart Plan with α & β Double Sampling Multiple Sampling Quality Control Techniques Control Charts Acceptance Sampling For Variables For Attributes Plan with α Single Sampling
Control Chart Issues
Size of sample 4-5
No. of samples 25
Frequency 5 units every half hour
Control Limits 3 std dev above and below mean
Control Charts for Variables
Mean control charts
Used to monitor the central tendency of a process.
X bar charts
Range control charts
Used to monitor the process dispersion
Variables generate data that are measured .
Control Chart for Variables
X Chart is simply a plot of the means of the samples that were taken from a process. X is the average of the means.
UCLx = X + 3 σ x = X + AR
LCLx = X - 3 σ x = X - AR
X = Mean of sample
X = Mean of sample means
σ x = sample std. error = σ /√n
Control Chart for Variables
R Chart is a plot of the range within each sample. R is the average of range of each sample.
UCL R = R + 3 σ R = BR
LCL R = R - 3 σ R = CR
R = Range
σ R = std. dev of R
Mean and Range Charts UCL LCL UCL LCL R-chart Detects shift Does not detect shift (process mean is shifting upward) Sampling Distribution x-Chart
Mean and Range Charts UCL Does not reveal increase UCL LCL LCL R-chart Reveals increase (process variability is increasing) Sampling Distribution x-Chart
Q- The following data was obtained over a 5 day period to indicate X and R control chart for a quality characteristic of a certain manufacturing product that had required substantial amount of rework. All the figures apply to the product made on a single machine by a single operator. Sample size is 5. Two samples are taken per day. Comment on the process using X and R charts.
P Chart is the percent defective chart based on Normal distribution
Its purpose –
discover the average % of non-conforming parts
bring to mgmt attention any change in the average quality level
UCL ρ = ρ + 3 √ ρ (1- ρ )/n = ρ + 3 σ ρ
LCL ρ = ρ - 3 √ ρ (1- ρ )/n = ρ - 3 σ ρ
ρ = process % defective
ρ = process mean %
n = sample size
Use of p-Charts
When observations can be placed into two categories.
Good or bad
Pass or fail
Operate or don’t operate
When the data consists of multiple samples of several observations each
Q- Completed forms from a particular department of an Insurance Company were sampled daily to check the performance quality of that department. 1 sample of 100 units was collected each day for 15 days.
Develop p chart using 95% confidence level (1.96 σ p)
Plot the 15 samples collected
What comments can you make about the process
Numerical contd. 3 14 1 7 1 15 1 13 8 6 2 12 2 5 7 11 0 4 2 10 5 3 4 9 3 2 3 8 4 1 No. of Forms with Errors Sample No. of Forms with Errors Sample
C Chart is the no. of defectives/ sample area based on Poisson distribution
UCL c = C + 3 √C
LCL c = C - 3 √C
C = mean number of non-conformities
Use of c-Charts
Use only when the number of occurrences per unit of measure can be counted; non-occurrences cannot be counted.
Scratches, chips, dents, or errors per item
Cracks or faults per unit of distance
Breaks or Tears per unit of area
Bacteria or pollutants per unit of volume
Calls, complaints, failures per unit of time
Q- β electronic company manufactures resistors on mass production basis. At some intermediate point of production line, 10 samples of size 100 each have been taken. Resistors within each sample were classified into good or bad. The related data are given in the following table. Construct p chart with 3 sigma limit and comment on the process.