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Unformatted text preview: 1 INDE 321 Quality Control Chapter 10: Other Univariate Statistical Process Monitoring and Control Techniques Instructor : Linda Boyle University of Washington, ISE and CEE 2 Chapter 10 Discuss the latest developments in SPC SPC for Short Production Runs How to modify conventional control charts for Short Runs Modified and Acceptance control charts Control Charts for SixSigma Processes 3 SPC for Short Production Runs Example of short production runs Jobshop manufacturing (as opposed to an assembly line) Jobshop: produces specialty items (e.g., made to order parts) Typically less than 50 units total on a production run Therefore, not enough units to establish control limits. 4 SPC for Short Production Runs Measure deviation from nominal instead of the measured variable in the control chart (DNOM). Zero corresponds to the correct (or ideal value) Deviations include positive and negative values to represent distance from true height (e.g., +2 and 0.5) 5 Procedure for Deviation from NOMinal (DNOM) control chart 1. Calculate x i = M i T k Where x i is the deviation from nominal for each observation. M i is the i th actual measurement and T k is the target value for a particular group or part 1. Calculate and R For each subgroup using the deviations. 1. Construct standard and R charts For the deviations calculated. x x DNOM control charts 6 DNOM control charts Important points about DNOM approach 1. The Assumption: Process standard deviation is approximately the same for all parts. If NOT the same , use standardized and R charts. 1. This procedure works best when the sample size is constant for all part numbers 2. If the nominal specification is the desired target value for the process, DNOM is great! x 7 Example: DNOM control charts Problem 10.1 (page 488) Set up short run xbar and R chart using DNOM approach Four part types produced, A, B, C, and D Given: T A =100 (5 subgroups) T B =60 (3 subgroups) T C =75 (6 subgroups) T D =50 (6 subgroups) 8 Sample Number Part Type M 1 M 2 M 3 1 A 105 102 103 2 A 101 98 100 3 A 103 100 99 4 A 101 104 97 5 A 106 102 100 6 B 57 60 59 7 B 61 64 63 8 B 60 58 62 9 C 73 75 77 10 C 78 75 76 11 C 77 75 74 12 C 75 72 79 13 C 74 75 77 14 C 73 76 75 15 D 50 51 49 16 D 46 50 50 17 D 51 46 50 18 D 49 50 53 19 D 50 52 51 20 D 53 51 50 9 Sample Number Part Type X 1 X 2 X 3 1 A 5 2 3 2 A 12 3 A 31 4 A 1 43 5 A 6 2 6 B31 7 B 1 4 3 8 B2 2 9 C2 2 10 C 3 1 11 C 21 12 C3 4 13 C1 2 14 C2 1 15 D 11 16 D4 17 D 14 18 D1 3 19 D 2 1 20 D 3 1 10 Control Charts R A x LCL x CenterLine R A x UCL 2 2 = = + = R D LCL R CenterLine R D UCL 3 4 = = = 11...
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This note was uploaded on 04/26/2010 for the course INDE 321 taught by Professor Boyle during the Winter '10 term at University of Washington.
 Winter '10
 Boyle

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