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Quality Control

Quality Control

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Quality Control

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  1. Quality Control COB 300 C - The Operations Dimension Busing

  2. Causes of Variation • Random Causes • difficult or expensive to control • e.g., outside humidity, line voltage • Assignable Causes • easier to correct • e.g., employee error, new materials

  3. Comparing Process Variation to Tolerance Limits

  4. High Process Capability After Technological Process Change

  5. Control Charts • Variables - concentrates on mean for some measurable characteristic. • diameter • length • Attribute - data is based on counts or the number of times we observe a particular event. • proportion defective/non-defective • go/no go • proportion pass/fail

  6. Control Limits - Variables Charts X-Bar Chart R Chart

  7. Factors for Control Limits(Slide 1 of 2) Sample of Size n A D D 2 3 4 2 3 4 5 6 7 8 9 10 1.880 1.023 0.729 0.577 0.483 0.419 0.373 0.337 0.308 0 0 0 0 0 0.076 0.136 0.184 0.223 3.268 2.574 2.282 2.114 2.004 1.924 1.864 1.816 1.777

  8. x-bar Chart Example (cont’d)

  9. Range Chart

  10. Warning Conditions • Two successive points near limit • Run of five above or below mean • Trend • Erratic behavior

  11. Process Control for Attributes Proportion defective: Number of defects per unit: