Introduction to Statistical Quality Control 1 What is Statistical Quality Control?  Statistical  Quality  Control  Statistical Quality Control - SQC 2 “Statistical”  What does the term statistical imply? 3 “Control”  What does the term control imply? 4 What is Quality? 5 What is Quality?  Traditional definition of Quality:  Product focused  Fitness of use - products must meet the requirements of users. 6 Dimensions of Quality (Products)       Performance – Will the product do the intended job? Reliability – How often does the product fail? Durability - How long does the product last? Serviceability – How easy is it to repair the product? Aesthetics – What does the product look like? Features – What does the product do? 7 Dimensions of Quality  In addition to products there is quality of:  Dimensions 8 Two Aspects of “Fitness for Use”  Quality of design –   Products are designed to be in various grades of quality. (e.g., Autos differ with respect to size, options, speed, etc.) Service systems are designed for different grades of quality  Quality of conformance –  How well the product conforms to specifications. (e.g., If diameter of a drilled hole is within specifications then it has good quality.)  Does the service representative follow guidelines? 9 A General Definition of Quality  Quality can viewed in multiple ways  To study quality and develop quality analysis approaches, a more general definition is needed 10 A General Definition of Quality  Quality is inversely proportional to Variability  If the variability of an important product characteristic decreases  quality of product increases  Quality Improvement –  Reduction of variability in processes and products. 11 Examples 12 A General Definition of Quality  Characterizing variability is generally quantitative and data driven.  Reducing variability in some product/service characteristic forces more in depth exploration and knowledge of the design and production or delivery processes. 13 Summary  SPC embodies statistical methods focusing on monitoring and reducing variability.  Our initial focus will be on basic statistical concepts and analysis methods. 14 Quality in Industry  Terminology  Where quality control is applied  Six-Sigma 15 Terminology  Quality Engineering –  Set of operational, managerial, and engineering activities that a company uses to ensure that quality characteristics of a product/service are at nominal levels  Quality planning  Quality assurance  Quality control and improvement 16 Terminology  Quality planning  Strategic: Customers and their needs, products, measures,…  Quality assurance  Policies, procedures, work instructions, specifications, records, etc. for making sure products meet desired quality levels  Quality control and improvement  Monitoring specific results and identifying ways to eliminate causes of unsatisfactory results (reduce variability) 17 Where Quality Control is Applied  “An ounce of prevention is worth a pound of cure” 18 Acceptance Sampling  Sample from lot to determine acceptance  More efficient than 100% inspection  Reduces bad product sent to consumer  Dodge & Romig 1930s  No feedback, prevention or improvement 19 On-Line Process Control  Monitoring of manufacturing process measures with control charts  Shewhart 1920s  Sample & stop process if necessary  No improvement, but maintains current process 20 Off-Line Improvement  Designed experiments  Taguchi & Classical Statistics 1980s  Continuous improvement of product designs and manufacturing processes  Identification of “leverage” relative to improvement  Optimization of process parameters 21 Statistical Methods for Quality Control & Improvement  Method - Relative Savings  Acceptance Sampling ($1)  On-Line Process Control ($10)  Off-Line Process Improvement ($100) 22 Six Sigma - Motorola  Six Sigma = 2 defects per billion opportunities!  Applied ubiquitously (originally production focused)     identify problem; develop measurement; set goal; close gap  Utilizes statistical methods  Training levels defined for personnel 23 DMAIC – Chapter 2  DMAIC is a structured problem-solving technique consisting of the following steps:      Define Measure Analyze Improve Control  DMAIC is usually associated with six sigma. Reading  Text coverage of the introductory material  Chapter 1  Chapter 2  Reading assignment  Chapter 3 – see syllabus  Reminder:  There is a lab this week. 25