Chapter 3 - The basic tools of quality management - P1.pdf

Chapter 3 STATISTICAL TOOLS IN CONTROLLING PROCESS (part 1) Nguyễn Thị Hoàng Mai Learning outcomes LO2 – Interpret and apply statistical tools in controlling processes 2 I The basic quality tools (7 QC tools) II Process capability analysis Content 3 THE BASIC QUALITY TOOLS (7 QC TOOLS)...

Chapter 3 STATISTICAL TOOLS IN CONTROLLING PROCESS (part 1) Nguyễn Thị Hoàng Mai Learning outcomes LO2 – Interpret and apply statistical tools in controlling processes 2 I The basic quality tools (7 QC tools) II Process capability analysis Content 3 THE BASIC QUALITY TOOLS (7 QC TOOLS) 4 Introduction • One of the best technical tools for improving product and service quality is statistical process control (SPC). • The objective of a process control system is to: • provide a statistical signal when assignable causes of variation are present. • detect and eliminate assignable causes of variation. 5 Introduction Natural Variations • Also called common causes • Affect virtually all production processes • Expected amount of variation • Output measures follow a probability distribution • For any distribution there is a measure of central tendency and dispersion • If the distribution of outputs falls within acceptable limits, the process is said to be “in control” 6 Introduction Assignable Variations • Also called special causes of variation • Generally, this is some change in the process • Variations that can be traced to a specific reason • The objective is to discover when assignable causes are present • Eliminate the bad causes • Incorporate the good causes 7 Introduction 8 Flowchart 9 Flowchart • Is also known as process maps, process flowcharts, and process flow diagrams. • Is a graphical representation of all the steps involved in an entire process or a particular segment of a process. • Is effectively used in the first stages of problem-solving. Problem or non-valueadded activities nested within a process are easily identified. 10 Flowchart Steps to create a flowchart: 1. Define the process boundaries. 2. Define the process steps. Use brainstorming to identify the steps for new processes. For existing processes, actually, observe the process in action. 3. Sort the steps in the order of their occurrence in the process. Show related steps and how they merge. 4. Place the steps in appropriate flowchart symbols and create the chart. 11 Flowchart 12 13 14 15 Flowchart Benefits of using flowcharts: • People who work on the process can easily understand the process. • Improvements can be easily identified. • Improve communication between departments and production areas. • Motivate employees for quality efforts and continue to make recommendations for further improvements. • A valuable tool for new employee training programs. 16 Check sheet 17 Check sheet • In the early stages of process improvement, it will often become necessary to collect either historical or current operating data about the process under investigation • The check sheet is a form (document) used to collect data in real-time at the location where the data is generated. • The main purpose of check sheets is to ensure that the data is collected carefully and accurately by operating personnel. 18 19 20 21 22 Location damaged due to transportation 23 Check sheet Steps to Create a Check Sheet 1. Clarify the measurement objectives. “What is the problem?”, “Why should data be collected?”, “Who will use the information being collected?”, “Who will collect the data?” 2. Prepare a form for collecting data. Determine the specific things that will be measured and write this down on the left side of the check sheet. Determine the time or place being measured and write this across the top of the columns. 3. Collect the data for the items being measured. Record each occurrence directly on the check sheet as it happens. 4. Tally the data by totaling the number of occurrences for each category being measured. 24 Check sheet Applications of a Check Sheet • To distinguish between fact and opinion • To gather data about how often a problem occurs • To gather data about the type of problems that occur • When data can be observed and collected repeatedly by the same person or at the same location. • When collecting data on the frequency or patterns of events, problems, defects, defect location, defect causes, etc. • When collecting data from a production process. 25 Histogram 26 Histogram • A histogram is a graphical representation of the distribution of numerical data. • It is an estimate of the probability distribution of a continuous variable (quantitative variable) • Data are organized in a histogram to allow those investigating the process to see any patterns in the data that would be difficult to see in a simple table of numbers. 27 Histogram Applications of a Histogram • When the data are numerical and you want to see the shape of the distribution, especially to determine whether the output of a process is distributed normally • To analyze whether a process can meet the customer’s requirements • To analyze what the output from a supplier’s process looks like • When seeing whether a process change has occurred from one time period to another • To determine whether the outputs of two or more processes are different • When you wish to communicate the distribution of data quickly and easily to others 28 Working time (in working days) of workers in ABC company 29 30 Histogram 1. Collect and count the number of measurement 2. Determine the largest and smallest measurement 3. Select the number of intervals 4. Find interval size: l = interval size= Number of data < 50 50 – 100 100 – 250 > 250 Number of interval 5 -7 6 – 10 7 – 12 10 – 20 (largest measurement −smallest measurement) number of interval 5. Determine starting point of classes 6. Construct measurement scale 7. Count frequency of data 8. Prepare the histogram 31 Histogram Example: The spelling test scores for 20 students on a 50-words spelling test are given below. The scores (number correct) are 48, 49, 50, 46, 47, 47, 35, 38, 40, 42, 45, 47, 48, 44, 43, 46, 45, 42, 43, 47. Construct the histogram. 32 Histogram 33 References Hùng, B.N & Loan, N.T.Q (2017). Quản lý chất lượng. NXB Đại học Quốc gia TP. HCM Heizer, J., Render, B. & Munson, C. (2017). Operations Management: Sustainability and Supply Chain management (12th ed.). Pearson Education, Inc. Juran, J.M & Godfrey, A.B. (1999). Juran’s Quality Handbook, 5th Ed. Mc. Graw-Hill Juran, J.M., De Feo, J. A. (2010). Juran’s Quality Handbook, 6th Ed. Mc. Graw-Hill Montgomery, D. C. (2012). Statistical Quality Control, 7th Ed. John Wiley & Sons Nhà xuất bản Trẻ (2005). Tìm hiểu chất lượng có phải như bạn nghĩ không. Nhà xuất bản Trẻ Charantimath, P. M. (2017). Total Quality Management, Third Edition. Pearson India Education. Mitra, A. (2016). Fundamentals of quality control and improvement, Fourth Edition. Wiley. Besterfield, D.H., et al., (2012/2009). Total Quality Management, Third/Seccond Edition. Pearson India Education. Montgomery, D. C. (2013). Statistical Quality Control, Seventh Edition. John Wiley & Sons. 34 Thanks for your attention