Lecture Operations management: Creating value along the supply chain (Canadian edition) - Chapter 3

Chapter 3 statistical process control. This chapter includes contents: Basics of statistical process control, control charts, control charts for attributes, control charts for variables, control chart patterns, SPC with excel and OM tools, process capability.

OPERATIONS MANAGEMENT: Creating Value Along the Supply Chain, Canadian Edition Robert S Russell, Bernard W Taylor III, Ignacio Castillo, Navneet Vidyarthi CHAPTER Statistical Process Control Learning Objectives — Explain the basics of applying statistical process control (SPC) in production and services — Discuss the rationale and procedure for the initial construction of a control chart — Use attribute control charts — Use variable control charts — Identify control chart patterns and describe appropriate data collection — Evaluate the process capability of a process 3-2 Lecture Outline —Basics of Statistical Process Control —Control Charts —Control Charts for Attributes —Control Charts for Variables —Control Chart Patterns —SPC with Excel and OM Tools —Process Capability 3-3 Statistical Process Control (SPC) — Statistical Process Control — monitoring production process to detect and prevent poor quality — Sample — subset of items produced to use for inspection — Control Charts — process is within statistical control limits UCL LCL 3-4 Process Variability —Random • inherent in a process • depends on equipment and machinery, engineering, operator, and system of measurement • natural occurrences —Non-Random • special causes • identifiable and correctable • include equipment out of adjustment, defective materials, changes in parts or materials, broken machinery or equipment, operator fatigue or poor work methods, or errors due to lack of training 3-5 SPC in Quality Management —SPC uses —Is the process in control? —Identify problems in order to make improvements —Contribute to the TQM goal of continuous improvement 3-6 Quality Measures: Attributes and Variables —Attribute —A characteristic which is evaluated with a discrete response —good/bad; yes/no; correct/incorrect —Variable measure —A characteristic that is continuous and can be measured —Weight, length, voltage, volume 3-7 SPC Applied to Services — Nature of defects is different in services — Service defect is a failure to meet customer requirements — Monitor time and customer satisfaction 3-8 SPC Applied to Services —Hospitals — timeliness & quickness of care, staff responses to requests, accuracy of lab tests, cleanliness, courtesy, accuracy of paperwork, speed of admittance & checkouts —Grocery stores — waiting time to check out, frequency of out-of-stock items, quality of food items, cleanliness, customer complaints, checkout register errors —Airlines — flight delays, lost luggage & luggage handling, waiting time at ticket counters & check-in, agent & flight attendant courtesy, accurate flight information, cabin cleanliness & maintenance 3-9 SPC Applied to Services —Fast-food restaurants — waiting time for service, customer complaints, cleanliness, food quality, order accuracy, employee courtesy —Catalogue-order companies — order accuracy, operator knowledge & courtesy, packaging, delivery time, phone order waiting time —Insurance companies — billing accuracy, timeliness of claims processing, agent availability & response time 3-10 Control Chart Patterns 3-42 Control Chart Patterns 3-43 Zones for Pattern Tests 3-44 Performing a Pattern Test 3-45 Sample Size Determination —Attribute charts require larger sample sizes —50 to 100 parts in a sample —Variable charts require smaller samples —2 to 10 parts in a sample 3-46 Process Capability —Compare natural variability to design variability —Natural variability —What we measure with control charts —Process mean = 8.80 oz, Std dev = 0.12 oz —Tolerances —Design specifications reflecting product requirements —Net weight = 9.0 oz 0.5 oz —Tolerances are 0.5 oz 3-47 Process Capability 3-48 Process Capability 3-49 Process Capability Ratio Cp = = tolerance range process range upper spec limit - lower spec limit 3-50 Computing Cp Net weight specification = 9.0 oz 0.5 oz Process mean = 8.80 oz Process standard deviation = 0.12 oz upper specification limit lower specification limit Cp = = 9.5 - 8.5 6(0.12) = 1.39 3-51 Process Capability Index = x - lower specification limit , Cpk = minimum upper specification limit - x 3-52 = Computing Cpk Net weight specification = 9.0 oz 0.5 oz Process mean = 8.80 oz Process standard deviation = 0.12 oz Cpk = minimum = minimum = x - lower specification limit , = upper specification limit - x 8.80 - 8.50 9.50 - 8.80 3(0.12) , 3(0.12) = 0.83 3-53 Process Capability With Excel 3-54 Process Capability With OM Tools 3-55 COPYRIGHT Copyright © 2014 John Wiley & Sons Canada, Ltd All rights reserved Reproduction or translation of this work beyond that permitted by Access Copyright (The Canadian Copyright Licensing Agency) is unlawful Requests for further information should be addressed to the Permissions Department, John Wiley & Sons Canada, Ltd The purchaser may make back-up copies for his or her own use only and not for distribution or resale The author and the publisher assume no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information contained herein ... 22 23 24 25 Factor for X-chart A2 1.880 1.0 23 0.729 0.577 0.4 83 0.419 0 .37 3 0 .33 7 0 .30 8 0.285 0.266 0.249 0. 235 0.2 23 0.212 0.2 03 0.194 0.187 0.180 0.1 73 0.167 0.162 0.157 0.1 53 Factors for R-chart... Factors for R-chart D3 0.000 0.000 0.000 0.000 0.000 0.076 0. 136 0.184 0.2 23 0.256 0.2 83 0 .30 7 0 .32 8 0 .34 7 0 .36 3 0 .37 8 0 .39 1 0.404 0.415 0.425 0. 435 0.4 43 0.452 0.459 D4 3. 267 2.575 2.282 2.114... = p - z p(1 - p) = 0.10 - n 0.10(1 - 0.10) 100 LCL = 0.010 3- 1 9 Construction of p-Chart 3- 2 0 p-Chart in Excel Click on “Insert” then “Charts” to construct control chart I4 + 3* SQRT(I4*(1-I4)/100)