MSA and Process Capability

Question 1

Measurement Systems Analysis MSA

Answer 1

analysis to determine what variation is from the actual process or the measurement system in place

Question 2

MSA involves

Answer 2

• selecting the correct measurement and approach
• assessing the measuring device
• assessing procedures and people conducting measurements
• assessing any measurements interacions
• calculating the measurement uncertainty of individual measurement devices and/or measurement systems

Question 3

MSA elements

Answer 3

MS - accuracy
                       . linearity
                       . Bias
                       . Stability
      - Precision
                       . repeatability
                       . reproducibility
                            , operator 
                         part interaction
                            , operator

Question 4

accuracy in terms of MSA

Answer 4

the difference between the measurement and the parts actual value

Question 5

precision in terms of MSA

Answer 5

the variation you see when you measure the same part repeatedly with the same gauge

Question 6

True value

Answer 6

theoretically correct value

Question 7

bias

Answer 7

difference between the average value of all measurements of a sample and the true value for that sample

Question 8

stability

Answer 8

stable processes are those that are free from special cause variation

Question 9

Linearity

Answer 9

a measure of any change in accuracy or precision over range of instrument capability

Question 10

repeatability

Answer 10

variability inherent in the measurement system under constant conditions

Question 11

reproducibility

Answer 11

variability among measurement made under different conditions

Question 12

source of poor measurement

Answer 12

poor/nonexistent operational definitions
lack of understanding of the definitions
difficult measures
poor sampling

Question 13

specification limits

Answer 13

• derived from customer requirements

- allowable range of product deviation from the customers requirements that he/she is willing to accept

Question 14

Process Capability

Answer 14

Ability of a process to meet its specifications

• measures the performance of a process
• process must be stable in order to calculate process capability

Question 15

process capability measures

Answer 15

Cp index: measures the process potential

Cpk index: measures the process capability but take into account the of off-centredness of a process

Question 16

Cp equation

Answer 16

(USL-LSL)/(6*deviation)

Question 17

corrective approaches to increase process potential

Answer 17

increase the specification limits

reduce the process spread

Question 18

limitations of process capability

Answer 18

does not incorporate the process mean or process centring
-process can be capable and still not meet the customer needs
Cpk takes process centring and variation

Question 19

Cpk, process capability index equation

Answer 19

Cpk = min [ ((USL-u)/3sigma), ((u-LSL)/3 sigma)]

Question 20

Desired Cpk

Answer 20

> 1

Question 21

Reasons for sampling

Answer 21

to save time, money and effort
-we can draw relatively accurate conclusions about the population from sample (if sample is representative)
 --appropriate sampling 
    method
 --appropriate sample size
-impossible to examine all population
--too large
--sampling is destructive
--£££

Question 22

Samping approaches

Answer 22

random sampling
systematic sampling
subgroup sampling
stratified sampling