文档介绍：Process Capability & Statistical Quality Control
Operations Management
petitive Advantage
CHASE AQUILANO JACOBS
ninth edition
Technical Note 7
Technical Note 7 Process Capability and Statistical Quality Control
Process Variation
Process Capability
Process Control Procedures
Variable data
Attribute data
Acceptance Sampling
Operating Characteristic Curve
Basic Forms of Variation
Assignable variation is caused by factors that can be clearly identified and possibly managed.
Common variation is inherent in the production process.
Taguchi’s View of Variation
Incremental
Cost of
Variability
High
Zero
Lower
Spec
Target
Spec
Upper
Spec
Traditional View
Incremental
Cost of
Variability
High
Zero
Lower
Spec
Target
Spec
Upper
Spec
Taguchi’s View
Exhibits &
Process Capability
Process limits
Tolerance limits
How do the limits relate to one another?
Process Capability Index, Cpk
Shifts in Process Mean
Capability Index shows how well parts being produced fit into design limit specifications.
As a production process produces items small shifts in equipment or systems can cause differences in production performance from differing samples.
Types of Statistical Sampling
Attribute (Go or no-go information)
Defectives refers to the acceptability of product across a range of characteristics.
Defects refers to the number of defects per unit which may be higher than the number of defectives.
p-chart application
Variable (Continuous)
Usually measured by the mean and the standard deviation.
X-bar and R chart applications
UCL
LCL
Samples over time
1 2 3 4 5 6
UCL
LCL
Samples over time
1 2 3 4 5 6
UCL
LCL
Samples over time
1 2 3 4 5 6
Normal Behavior
Possible problem, investigate
Possible problem, investigate
Statistical Process Control (SPC) Charts
Control Limits are based on the Normal Curve
x
0
1
2
3
-3
-2
-1
z
m
Standard deviation units or “z” units.
Control Limits
We establish the Upper Control Limits (UCL) and