Presentation on theme: "My Personal Crusade Mark S. Rusco Innovative Corporate Training"— Presentation transcript:
My Personal Crusade Mark S. Rusco Innovative Corporate Training
Each is just a Standard Deviation. From Page 115 of the MSA (2 nd Paragraph) And from Page vi
Page 55 reminds us to add variances, not standard deviations.
X XXX XXXX
X XXX XXXX
X XXX XXXX
X XXX XXXX This Standard Deviation defines the Error of Width This distance defines Error of Location
Bias Linearity Stability Averaging several readings does not help. Found by measuring known standards. Eliminate/minimize by calibration.
Repeatability Reproducibility Averaging several readings reduces error. Found by repeated measurements of the same parts. Minimize by operator training, gauge improvement, etc.
R & R are both Standard Deviations We combine them as Variances to get GRR Theres a major difference between Errors of Location and Errors of Width.
Pg 74, in bold letter, tells us how to sample
selected from the process is not: Consecutive parts Random Parts At least one part should be as small as normally expected, and one part should be as large as normally expected. All the other in- between parts dont really matter.
Start with Equation for %GRRtv
Substitute in EV and AV for RR. Substitute in RR and PV for TV
Substitute in EV and AV for RR on the bottom %GRR tv is driven by PV.
What drives PV? PV = R p x K 3 R p = Biggest Part – Smallest Part You want R p to be as big as possible, so %GRR tv is as small as possible.
Sort through your parts to find the biggest and smallest part you can find. This makes R p big, which makes PV big, which makes %GRR tv small. Small %GRR tv makes your life easier.
You know the Standard Deviation of your Gauge System. Is it a good gauge? Can the gauge discriminate between Good/Bad Parts? Can the gauge detect process variation?
Can the gauge discriminate between Good/Bad Parts? Answered by %GRR tot tol
Can the gauge detect process variation? Answered by %GRR tv
Just because %GRR tv <10% and %GRR tot tol <10% doesnt mean the situation is good. Which situation is better for your company? %GRRtv = 6% and %GRRtt = 9% OR %GRRtv = 15% and %GRRtt = 9%
Understand the difference between %GRR tot tol and %GRR tv Dont plug your data into software and blindly accept the %GRR values.