1 / 21

Quality Control

Quality Control. Ross L. Fink. Quality Control. Quality control involves controlling the delivery processes to adhere to the specifications (or product design). Quality Control Approaches. 100 % Inspection Acceptance Sampling Statistical Process Control (SPC) or Control-Chart Method.

hyatt-levine
Download Presentation

Quality Control

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Quality Control Ross L. Fink

  2. Quality Control • Quality control involves controlling the delivery processes to adhere to the specifications (or product design).

  3. Quality Control Approaches • 100 % Inspection • Acceptance Sampling • Statistical Process Control (SPC) or Control-Chart Method

  4. Acceptance Sampling Accept or Reject Entire Lot Based Upon Quality of Sample

  5. Statistical Process Control • Basic Approach • Take one sample of size 5 each hour • Measure quality characteristic • Plot measurement over time (sample number)

  6. Run Chart

  7. Distribution of Measurement on Control Chart • Since we are taking a mean, the Central Limit Theorem of the Sample Mean applies • Therefore, mean follows a normal distribution. • Three Sigma Limits

  8. Plot of Mean

  9. Theory of Control Charts • Purpose of control charts is to separate natural variability (common cause) from nonrandom variability (assignable cause). • In-control (common cause) versus out-of-control (assignable cause).

  10. Types of Variability

  11. X-bar Chart

  12. Control Chart Rules • Simple Rules • One point above UCL • One point below LCL • Most organizations use more complex rules • e.g., seven consecutive points increasing

  13. Constructing a Control Chart • Obs. 1 2 3 4 5 • Sample • 1 11.63 14.44 14.52 17.58 12.71 • 2 13.30 16.21 15.04 16.09 14.19 • 3 12.60 11.49 14.73 15.58 17.41 • 4 13.68 13.49 13.24 16.98 16.23 • 5 15.12 15.21 11.69 14.91 16.36 • 6 15.70 16.09 16.78 15.48 14.56 • 7 13.46 14.28 17.09 13.84 15.85 • 8 14.22 13.90 14.47 15.18 19.31 • 9 12.44 15.12 16.00 14.62 16.05 • 10 14.04 14.88 19.26 14.37 16.35 • 11 12.42 13.25 15.56 15.18 14.13 • 12 15.65 12.94 16.16 15.98 18.67 • 13 15.71 13.78 14.19 16.02 13.78 • 14 14.80 12.17 16.00 12.93 12.34 • 15 15.63 12.14 14.98 16.61 14.21 • 16 10.13 15.43 17.09 17.72 18.72 • 17 13.73 15.26 13.53 14.43 15.22 • 18 11.44 17.00 13.72 13.11 13.80 • 19 10.72 10.12 15.80 19.72 11.72 • 20 15.43 15.00 15.58 14.99 15.40

  14. Find Sample Means and Ranges • Obs. 1 2 3 4 5 Mean Range • Sample • 1 11.63 14.44 14.52 17.58 12.71 14.18 5.95 • 2 13.30 16.21 15.04 16.09 14.19 14.96 2.93 • 3 12.60 11.49 14.73 15.58 17.41 14.36 5.92 • 4 13.68 13.49 13.24 16.98 16.23 14.72 3.75 • 5 15.12 15.21 11.69 14.91 16.36 14.66 4.67 • 6 15.70 16.09 16.78 15.48 14.56 15.72 2.22 • 7 13.46 14.28 17.09 13.84 15.85 14.90 3.63 • 8 14.22 13.90 14.47 15.18 19.31 15.42 5.39 • 9 12.44 15.12 16.00 14.62 16.05 14.85 3.62 • 10 14.04 14.88 19.26 14.37 16.35 15.78 5.22 • 11 12.42 13.25 15.56 15.18 14.13 14.11 3.14 • 12 15.65 12.94 16.16 15.98 18.67 15.88 5.72 • 13 15.71 13.78 14.19 16.02 13.78 14.70 2.23 • 14 14.80 12.17 16.00 12.93 12.34 13.65 3.83 • 15 15.63 12.14 14.98 16.61 14.21 14.71 4.47 • 16 10.13 15.43 17.09 17.72 18.72 15.82 8.59 • 17 13.73 15.26 13.53 14.43 15.22 14.43 1.73 • 18 11.44 17.00 13.72 13.11 13.80 13.81 5.56 • 19 10.72 10.12 15.80 19.72 11.72 13.61 9.60 • 20 15.43 15.00 15.58 14.99 15.40 15.28 0.59

  15. Calculate Grand Mean and Grand Range

  16. Control Limits

  17. Table • Factors for Computing Control Chart Limits • Sample Size Mean Factor Upper Range Lower Range • N A2 D4 D3 • 2 1.880 3.268 0 • 3 1.023 2.574 0 • 4 .729 2.282 0 • 5 .577 2.115 0 • 6 .483 2.004 0 • 7 .419 1.924 0.076 • 8 .373 1.864 0.136 • 9 .337 1.816 0.184 • 10 .308 1.777 0.223

  18. Control Limits

  19. X-bar Chart

  20. R Chart

  21. In-Control v. Out-Of-Control • What are the implications of being in-control? • What are the implications of being out-of-control?

More Related