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Version 2005_1SPC Design1 S tatistical P rocess C ontrol S P C.

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Presentation on theme: "Version 2005_1SPC Design1 S tatistical P rocess C ontrol S P C."— Presentation transcript:

1 Version 2005_1SPC Design1 S tatistical P rocess C ontrol S P C

2 Version 2005_1SPC Design2 Definitions Special Cause (also assignable causes) special causes refer to any factors of variation that are not always acting on the process. They affect the process in unpredictable ways. Common Cause common causes refer to the many sources of variation within a process that has a stable and repeatable distribution over time. The output is predictable.

3 Version 2005_1SPC Design3 Distribution Standard Normal Distribution Distribution of total points for the sum of three dices

4 Version 2005_1SPC Design4 Distribution Standard Normal Distribution Bell-shaped Curve (Gauß)

5 Version 2005_1SPC Design5 X Turning-Point s Standard Normal Distribution -6 6 

6 Version 2005_1SPC Design6 Glossary and Symbols ? Target and Prediction ???

7 Version 2005_1SPC Design7 Glossary and Symbols x : mean value compute the mean value, using the following formula: the sum of values from a given sample X = number of values (sample size)

8 Version 2005_1SPC Design8 Glossary and Symbols R s 2 s = RjRj m = s2js2j m = sjsj m average range of subgroups average variance average sample standard diviation Σ Σ Σ

9 Version 2005_1SPC Design9 Glossary and Symbols Upper Control Limit ( UCL ) line(s) on a control chart used as a basis for judging the stability of the process Formula: UCL R = D 4 * R UCL x = x + A 2 * R UCL s = B 4 * s UCL x = x + A 3 * s

10 Version 2005_1SPC Design10 Glossary and Symbols Lower Control Limit ( LCL ) line(s) on a control chart used as a basis for judging the stability of the process Formula: LCL R = D 3 * R LCL x = x - A 2 * R LCL s = B 3 * s LCL x = x - A 3 * s

11 Version 2005_1SPC Design11 Glossary and Symbols Upper Specification Limit ( USL ) Lower Specification Limit ( LSL ) upper/ lower engineering specification limit engineering requirement for judging acceptability of a particular characteristic

12 Version 2005_1SPC Design12 Process Potential & Capability Target Value LSL USL Customer Requirement Loss very good Loss Function good acceptable

13 Version 2005_1SPC Design13 Process Potential & Capability c p : Process Potential an index based on long-term observation of a process in a state of statistical control p p : Preliminary Process Potential short-term observation of process early information of new or changed process used for process and equipment development

14 Version 2005_1SPC Design14 Process Potential & Capability Potential of Process Capability of Process Spread of Process Spread of P. & Specification preliminaryp p pk long-termcpcp c pk

15 Version 2005_1SPC Design15 Process Potential & Capability PIST: Percent of Inspection points which Satisfy the Tolerance PIST = number of characteristics satisfying tolerance total number of characteristics x 100

16 Version 2005_1SPC Design16 Process Potential & Capability PIPC Percentage of Indices which are Process Capable PIPC = number of characteristics with p p / p pk  1,67 total number of characteristics x 100

17 Version 2005_1SPC Design17 Control Chart Header, information relating to plant, machine, shift, part number,..... X Bar Chart showing: USL, UCL, x,....., LSL, LCL results over time Ranges (R Chart) showing: USL, UCL, R,....., LSL, LCL results over time relating to: R, s, s 2 Individual readings, summary & dates explaning and relating to data for graph Reaktion Plan Quality References Instruction regarding computation,....

18 Version 2005_1SPC Design18 Control Chart Header, information relating to plant, machine, shift, part number,..... Process Log Sheet (Back of Page): Information relating any changes made to process: Example: new tooling, materials,..... change of shift, unplanned down time,..... maintenance, cleaning, all information that night be needed when investigating root causes of problems

19 Version 2005_1SPC Design19 Qualitätsregelkarte Interpretation/ Overadjustment Upper Specification Limit Upper Control Limit Upper Warning Limit Lower Warning Limit Lower Control Limit Lower Specification Limit Mean

20 Version 2005_1SPC Design20 Bibliography Statistical Process Control (SPC) Reference Manual, Chrysler, Ford, GM, Ausgabe 1995 The Memory Jogger II, GOAL/ QPC, First Edition, Methuen, Mass. USA 1994 Qualitätsmanagement von A-Z, Kaminske/ Bauer, Hanser Verlag, 2. Edition 1994 The Six Sigma Phenomenon, Mikel Harry, Richard Schroeder


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