Page 219 - DMGT524_TOTAL_QUALITY_MANAGEMENT
P. 219
Total Quality Management
Notes The R Control Chart
The center line and upper and lower control limits for an R chart are:
UCL = Dr
4
CL = r
LCL = Dr
3
where r is the sample average range, and the constants D and D are tabulated for various
3 4
sample sizes in Appendix Table of Control Charts.
Figure 14.13: Chances of getting a Reading beyond U&L is almost Nil
Target Process
Mean
L U
– 3 s + 3 s U – L = 6 s
42 43 44 45 46 47 48 49 50 51 52 53
When an observation falls within original +3s and – 3s zone of mean of a process, we conclude
that there is no shift in the mean of process. This is so because falling of an observation between
these limits is a chance.
Figure 14.14: Shift in Process
Small shift in process Process
Mean
L U
Target
42 43 44 45 46 47 48 49 50 51 52 53
When an observation falls beyond original +3s and – 3s zone of process mean, we conclude that
there is shift in location of the process.
Step 1: Select quality characteristics which needs to be controlled
Weight
Length
214 LOVELY PROFESSIONAL UNIVERSITY
