Ch 6 Variable CC - INDE 321 Quality Control Chapter 6,...

Info iconThis preview shows pages 1–18. Sign up to view the full content.

View Full Document Right Arrow Icon
Click to edit Master subtitle style 11 INDE 321 Quality Control Chapter 6, Variable Control Charts Instructor : Linda Boyle Industrial and Systems Engineering Civil and Environmental Engineering University of Washington
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
22 Control Charts n Two general types of control charts n Variables Control Charts n Apply to data that follows a continuous distribution (measurement data). n Attributes Control Charts n These charts are applied to data that follow a discrete distribution (count data, defects).
Background image of page 2
33 Control Charts for Variables n Variable - a single quality characteristic that can be measured on a numerical scale. Examples: Weight, Diameter, Age, Length n When working with variables, need to monitor… n the mean value of the characteristic and n the variability associated with the characteristic.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
44 Control Charts for Variables Purpose : to give information about the performance or capability of the process n R chart gives information on whether the process variability is in control n If process variability is in control, then can examine the chart.
Background image of page 4
55 Control Charts for Variables n = average of the observations in the i th sample (where i = 1, 2, . .., m) n = grand average or “average of the averages (this value is used as the center line of the control chart) i x x
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
66 Control Charts for Variables n Let’s say each point represented the average weight for samples collected each day. n and found n n packet 2 weighed 20 g n packet 3 weighed 35 g
Background image of page 6
77 Control Charts for Variables
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
88 Control Charts for Variables Statistical Basis of the Charts n Assume quality characteristic is normally distributed with mean , and standard deviation, . n If x1, x2, …, xn is a sample of size n, then the average of this sample is n is normally distributed with mean, , and standard deviation, n x x x x n 2 1 + + + = x n x / σ =
Background image of page 8
99 Control Charts for Variables Statistical Basis of the Charts n The probability is 1 - that any sample mean will fall between (LCL) (UCL) 2 / 2 / 2 / 2 / n Z Z and n Z Z x x σ μ α - = - + = +
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
1010 Control Charts for Variables n Ri = range of the values in the ith sample Ri = xmax - xmin n = average range for all m samples (subgroup)
Background image of page 10
1111 Control Charts for Variables n and found n n packet 2 weighed 20 g n packet 3 weighed 35 g
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
1212 Control Charts for Variables Estimating the Process Standard Deviation n Can be estimated using a function of the sample average range. n d2 is a function of the sample size (for each subgroup) n Example, if n=5, then d2=2.326 n d2 is defined as the mean of the relative ranges, W ( W=R/ σ ) n Values of d2 found in Appendix VI Obj1 4
Background image of page 12
1313 Control Charts for Variables A2
Background image of page 13

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
1414 Control Charts for Variables Control Limits for the chart x R A x LCL x Line Center R A x UCL 2 2 - = = + =
Background image of page 14
1515 Control Charts for Variables Control Limits for the R chart R D LCL R Line Center R D UCL 3 4 = = =
Background image of page 15

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
1616 Appendix VI A2=0.577 D3=0 D4=2.115
Background image of page 16
1717 Important things to note n Should always start by checking the variability of the process (is it stable over time?).
Background image of page 17

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 18
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 74

Ch 6 Variable CC - INDE 321 Quality Control Chapter 6,...

This preview shows document pages 1 - 18. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online