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IE 405 QUALITY MANAGEMENT

IE 405 QUALITY MANAGEMENT. RECITAITON FIVE: REVIEW SESSION FALL 2002. BASIC CONCEPTS OF QUALITY. Traditional definition: ‘FITNESS FOR USE’ QUALITY DIMENSIONS: Performance, Reliability, Durability, Serviceability, aesthetics, features, perceived quality and conformance to standards.

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IE 405 QUALITY MANAGEMENT

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  1. IE 405 QUALITY MANAGEMENT RECITAITON FIVE: REVIEW SESSION FALL 2002

  2. BASIC CONCEPTS OF QUALITY • Traditional definition: ‘FITNESS FOR USE’ QUALITY DIMENSIONS: Performance, Reliability, Durability, Serviceability, aesthetics, features, perceived quality and conformance to standards. QUALITY CONTROL: Operational techniques and the activities which sustain a quality of product or services that will satisfy given needs. e.g. inspection at the end of production, in-receiving inspection QUALITY ASSURANCE: All plant and systematic activities to provide adequate confidence that a product or service will satisfy a quality dimension. e.g. training the people, statistical process control, preventive maintenance programs for bottleneck machines QUALITY IMPROVEMENT: Reduction of variability in processes and products.

  3. STATISTICAL METHODS FOR QUALITY CONTROL AND IMPROVEMENT THREE MAJOR AREAS: • Statistical Process Control i.eControl charts for process monitoring 2. Design of Experiments i.e.Factorial Experiments 3. Acceptance Sampling

  4. CUSTOMER TYPES 1. Internal customer 2. External customer Possible questions: • Who is the customer? • Who are my customers? • What do they need? • What are their measures and expectations?

  5. Customer types continued… • INTERNAL CUSTOMER: Person within the company who receives the work of another and then adds his or her contribution to the product or service before passing it on to someone else. EXAMPLES: • In manufacturing, the internal customer is the next person down the line who builds the product. • In a restaurant, the chef has the waiters and waitresses as internal customers and the chef must meet their requirements if they are all to please their guests. • Sand Muller Operator to Mold Machine Operator • Shipping Supervisor to Billing Clerk

  6. Customer types continued… • EXTERNAL CUSTOMER:People outside who are the end user’s of a firm’s products and services. EXAMPLES: • Manufacturer of the nozzle for a gasoline pump has the oil company, the service station owner and you as the users as external customers. • An auto insurance company has brokers, customer service representatives and the insured as the external customers.

  7. QUALITY COSTS FourTypes of Costs: • Prevention • Appraisal • Internal Failure • External Failure costs

  8. QUALITY COSTS • Prevention Costs:All costs incurred in an effort to ‘make it right the first time’. i.e Training 2. Appraisal Costs:These are costs to determine conformance with quality standards. i.e. Inspection, Auditing

  9. QUALITY COSTS continued.. 3.Internal Failure Costs: Incurred when products, components, materials and services fail to meet quality requirements and this failure is discovered prior to the delivery of the product to the customer. i.e. scrap, yield losses 4.External Failure Costs: Occur when the product does not perform satisfactorily after it is supplied to the customer. i.e. complaint adjustment, returned product/material

  10. QUALITY COSTS MATRIX

  11. STATISTICAL PROCESS CONTROL TOOLS • HISTOGRAMS, CHECK SHEETS, SCATTER DIAGRAMS, DEFECT CONCENTRATION DIAGRAMS • PARETO CHART • CAUSE AND EFFECT DIAGRAM • CONTROL CHARTS

  12. Why do we use STATISTICAL PROCESS CONTROL TOOLS? IN ANY PRODUCTION PROCESS, REGARDLESS OF HOW WELL DESIGNED OR CAREFULLY MAINTAINED IT IS, A CERTAIN AMOUNT OF INHERENT OR NATURAL VARIABILITY WILL ALWAYS EXIST. .

  13. A process that is operating with only chance causes of variation present is said to be IN STATISTICAL CONTROL. Sources of variability that are not part of the chance cause,pattern as ‘assignable causes’. A process that is operating in the presence of assignable causes is said to be OUT OF CONTROL. Chance and Assignable causes of Quality Variation

  14. TYPES OF CONTROL CHARTS • VARIABLE CONTROL CHARTS: Data are usually continuous measurements, such as length, voltage or viscosity Exp. X chart, R chart, S chart • ATTRIBUTE CONTROL CHARTS: Are for discrete data often taking the form of counts. • Exp. P chart, np chart, c and u charts. CHART CONSIDERATIONS INCLUDE SAMPLE SIZE AND FREQUENCY

  15. Analysis of Patterns on Control Charts • A control chart may indicate and out-of-control condition either when one or more points fall beyond the control limits or when the plotted points exhibit some nonrandom pattern of behavior. • Therefore, the problem is one of pattern recognition, that is recognizing systematic or nonrandom patterns on the control chart and identifying the reasons for this behavior. THUS use SENSITIZING RULES. LOOK forCYCLING PATTERNS, TRENDS, SHIFTS IN PROCESS LEVEL AND STRATIFICATION

  16. SUMMARY OF SHEWART CONTROL CHARTS

  17. ADVANTAGES AND DISADVANTAGES OF CONTROL CHARTS • Attributes control charts have the advantage that several quality characteristics can be considered jointly an the unit classified as nonconforming if it fails to meet the specification on any one characteristic • Variable control charts provide much more useful information about process performance than does an attributes control chart. Specific information about the process mean and variability is obtained directly. • The most important advantage of X and R chartss is that they often provide an indication of impending trouble and allow operating personnel to take corrective action BEFORE any defectives are actually produced. Thus, X and R charts are leading indicators of trouble. • P charts (or c and u charts) will not react unless the process has already changed so that MORE NONCONFORMING UNITS are produced.

  18. Recitation 5 Q1

  19. Recitation 5 Q1

  20. C: count of nonconformities • Cbar=x/n= 141/25=5.64 • UCL=12,76 • LCL=-1,4 approximately 0

  21. Remember in this chart low values that do not have an assignable cause represent exceptionally good quality. • CANOE NO 132,172 AND 278 are out of control. Since canoes 132 and 278 have an assignable cause, they are dicarded, however canoe 172 maybe due to chance cause and not discarded in this case. • Revised c =141-20-14/25-2=4.65 • UCL=11.1 LCL=1.82 APPROX. 0

  22. Recitation 5 Q1

  23. Recitation 5 Q2

  24. Recitation 5 Q2

  25. N: sample size C: number of defects per sample U: Avg. No of Defects per unit u bar= c/n 706/516=1.37 • U bar=Centerline • UCL= 2.25 LCL=0,49

  26. Although it seems in statistical control the defect rate is high, almost 1.4 defects per unit. • Therefore, the company has decided to investigate the causes of the large number of defects

  27. Recitation 5 Q2

  28. Recitation 5 Q2

  29. It is clear that the process has changed, in particular that the average number of defects per unit has been significantly reduced. The values are in the range of 0.4 and 0.7, previously being 1.4.

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