LECTURE 6

LECTURE 6 - ENGR 4045U Quality Control Lecture 6 1 Schedule...

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ENGR 4045U Quality Control Lecture 6 1
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Schedule Week 3 Part III: Basic Methods of Statistical Process Control and Capability Analysis. Chapter 5: Methods and Philosophy of Statistical Process Control. Chapter 6: Control Charts for Variables. Week 4 Chapter 7: Control Charts for Attributes. Chapter 8: Process and Measurement System Capability Analysis. Week 5 Midterm-1 2
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Example The service life of a battery used in a cardiac pacemaker is assumed to be normally distributed. A random sample of 10 batteries is subjected to an accelerated life test by running them continuously at an elevated temperature until failure, and the following lifetimes (in hours) are obtained: 25.5, 26.1, 26.8, 23.2, 24.2, 28.4, 25.0, 27.8, 27.3, and 25.7 3
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Example (a) the manufacturer wants to be certain that the mean battery life exceeds 25 h. What conclusions can be drawn from these data (use α =0.05)? (b) construct a 90% two-sided confidence interval on mean life in the accelerated test (c) construct a normal probability plot of the battery life data. What conclusion can you draw? 4
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Test Hypothesis Control limits are inversely proportional to sample size n Where = 0.15 H0: = 1.5 H1: 1.5 Where L is distance of control limit from center line 5 w w w w w L LCL Line Center L UCL
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Process Improvement 6
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Out-Of-Control- Action-Plan 7
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Control Chart Considerations Economic factor, e.g. cost of sampling Type of variation Stationary behavior, means process data vary around mean in stable or predictable manner Uncorrelated means data are drawn at random from stable population Autocorrelated means successive data are dependent Nonstationary means process is unstable without fixed mean, such as chemical process 8
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Stationary, Uncorrelated, Nonstationary 9
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Choice of Control Limits Action Limits (outer limits using 3-sigma), where point outside this limit will need search for causes and corrective action is taken Warning Limits (inner limits using 2-sigma) Figure 5.9, Page 191 10
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Analysis of Patterns in Control Charts A run is the arrangement of consecutive points Run up for increasing values Run down for decreasing values Page 195, figure 5.13 The cyclic variability behavior can be eliminated using operator fatigue, raw material deliveries, heat or stress buildup 11
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12
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Remove Reasons for Variability 13 Western Electric or Zones Rules, with violation of rule 3
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Cause-Effect Diagram 14
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Cause-Effect-Diagram 15
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This note was uploaded on 10/18/2010 for the course ENGR 3360 taught by Professor Ahmadbarari during the Fall '10 term at UOIT.

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LECTURE 6 - ENGR 4045U Quality Control Lecture 6 1 Schedule...

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