Process Control

Question 1

Process Capability Index (Cp)

Answer 1

a measure of spread

actual process variability

USL - LSL
————-
6σ

upper specification limit (USL)
lower specification limit (LSL)
standard deviation (σ)

Question 2

Cpk

Answer 2

a measure of location

( μ - LSL / 3σ, USL - μ / 3σ )

upper specification limit (USL)
lower specification limit (LSL)
mean (μ)
standard deviation (σ)

Question 3

X-bar and R control charts

Answer 3

x̄ (mean) is a measure of location (accuracy)

R (range) is a measure of spread (precision)

Question 4

What Cp is acceptable

Answer 4

depends on importance for accuracy

example:
toy, Cp < 1
standard part, Cp = 1
aerospace, Cp > 1

Question 5

what are control charts used for

Answer 5

also known as Statistical Process Control (SPC) charts, are graphical tools used to monitor trends shifts, or any unusual patterns that may indicate problems. Control charts are widely used in manufacturing and other industries to ensure that processes remain consistent and within acceptable limits.