Six-Sigma9 - Measurement System Analysis There is much...

Info iconThis preview shows pages 1–11. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Measurement System Analysis There is much confusion on measurement terminology. There are four characteristics to examine in a gage system. Sensitivity The gage should be sensitive enough to detect differences in measurement as slight as one-tenth of the total tolerance specification or process spread, whichever is smaller. Inadequate discrimination will affect both the accuracy and precision of an operator's reported values. Reproducibility The "reliability" of the gage system or similar gage systems to reproduce measurements. The reproducibility of a single gage is customarily checked by comparing the results of different operators taken at different times. Gage reproducibility affects both accuracy and precision.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 Measurement System Error Precise but not accurate Accurate but not precise Not accurate or precise Accurate and precise
Background image of page 2
3 Accuracy of Measurement • Broken down into three components: 1. Stability: the consistency of measurements over time. 2. Accuracy: a measure of the amount of bias in the system. 3. Linearity: a measure of the bias values through the expected range of measurements.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 Precision of Measurement • Precision, aka Measurement Variation, can be broken down into two components: 1. Repeatability (Equipment variation): variation in measurements under exact conditions. 2. Reproducibility (Appraiser variation): variation in the average of measurements when different operators measure the same part.
Background image of page 4
5 110 100 90 80 70 60 50 40 30 15 10 5 0 Observed Frequency LSL USL Actual process variation - No measurement error Observed process variation - With measurement error 110 100 90 80 70 60 50 40 30 15 10 5 0 Process LSL USL How Does Measurement Error Appear?
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
6 Possible Sources of Process Variation We will look at “repeatability” and “reproducibility” as primary contributors to measurement error Stability Linearity Long-term Process Variation Short-term Process Variation Variation w/i sample Actual Process Variation Repeatability Calibration Variation due to gage Variation due to operators Measurement Variation Observed Process Variation System t Measuremen 2 ocess l Actua 2 ocess Observed 2 σ + = Pr Pr ity producibil 2 y peatabilit 2 System t Measuremen 2 Re Re + =
Background image of page 6
7 – Repeatability – Reproducibility
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
8 The term “repeatability” refers to: The inherent variability of the measuring system Variation that occurs when repeated measurements are made of the same item under absolutely identical conditions – Same operator – Same setup – Same units – Same environmental conditions
Background image of page 8
9 The term “reproducibility” refers to: The variation that results when different conditions are used to make the measurements – Different operators – Different setups – Different units – Different environmental conditions – Different measurement systems
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
10 Overall Variation
Background image of page 10
Image of page 11
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 42

Six-Sigma9 - Measurement System Analysis There is much...

This preview shows document pages 1 - 11. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online