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MIE364S_LH_1_09 - MIE364H1S Methods of Quality Control and...

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MIE364H1S Methods of Quality Control and Improvement Course Instructor: Prof. V. Makis Handout #1 A procedure of setting up control charts using historical data (should be recent history). Consider ) , ( X R charts. Data: m X X ,..., 1 and m R R ,..., 1 . 1. R chart with 3 sigma limits: Calculate R , R CL n D R UCL n D R LCL = = = ), ( ), ( 4 3 . If a point plots outside the control limits: a. A cause was found and was removed or disappeared Æ delete the point b. A cause was found and cannot be removed Æ keep the point c. No cause was found but not much information is available Æ delete the point d. No cause was found and we are quite sure that there was none Æ keep the point After deleting the points, recalculate new new new UCL and LCL R , , and plot the remaining points again. If you still have points outside the control limits after several iterations (say, 2), there is a major problem with the process, causes should be found using other SPC tools and removed. If all the points are between the limits, or you decide to keep the points outside (b. or d.), find
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