05-Average-Range Charts-class - Edited by Foxit Reader...

Section 5 - Variable Control Charts & Average-Range Charts
UGA FDST 4090/6090 - (c) W.C. Hurst 2009 1
Variable Control Charts
William C. Hurst FDST 4090/6090 (2009)
Variable Control Charts
• Process stabilization
–
Maintain process
EXAMPLES OF USE:
– Weight: fill, net, drained
(g, lb, oz)
– Temperature
– Volume (ml l oz)
FDST 4090/6090 © W.C. Hurst 2009
– Maintain process
control
• Process improvement
–
– Volume (ml, l, oz)
– pH
– A
w
(water activity)
– % Brix
– % RH
– Thickness (micrometer)
– ppm
Types of Variable Charts
• x-R
• x- s
FDST 4090/6090 © W.C. Hurst 2009
• μ , σ
• x-MR
Average and Range Charts (x-R)
1. Select measurable
characteristic and form
rational subgroups
2. x tracks
4. Control limits set based
on common cause
variation present
5. As subgroup size
increases control limits
FDST 4090/6090 © W.C. Hurst 2009
3. R tracks
increases, control limits
become closer to process
average, which makes
chart more sensitive to
small variations in
process, but inspection
costs also increase
Distribution of
Individuals and Averages
FDST 4090/6090 © W.C. Hurst 2009
n = 5
n = 1
Average – Range (x-R)
Charts
FDST 4090/6090 © W.C. Hurst 2009

Section 5 - Variable Control Charts & Average-Range Charts
UGA FDST 4090/6090 - (c) W.C. Hurst 2009 2
Problem 1
The Quality Assurance Manager at a DelMonte
fresh-cut plant has been asked by management
to monitor the filling process for freshly-cored
pineapple rings to determine if their weights are
FDST 4090/6090 © W.C. Hurst 2009
in or out of statistical control.