Gage R&R - RTT (Total Spec) - New tecnique to calculate R&R involving Six Sigma

[chuy sanchez]

A friend just told me that a new tecnique to calculate r&r involving 6 sigma ( no from g.e.concept) so, somebody hear about that ?

Only that i know is when you relations is with RTT( total Spec ).

thanks

 

[Marc]

I''m not an R&R expert. Maybe one of the other folks can pick up on this.

 

[Don Winton]

I have not heard anything "new" regarding R&R either.

Regards,

Don

 

[Batman]

I am not a statistamagician, but on occasion I have used a 6 sigma vs total tolerance when using a CMM or similar instrument and only needed the "R" repeatability part of the Gage error.

I take one part and measure it 20 times (not sure how significant THAT value is - 15 may be enough) and calculate the 6 sigma of those values. Theoretically, this give the error of the measurement device, which is then compared to the total tolerance.

I don't recall reading this anywhere, but no one ever complained.

 

[chuy sanchez]

yeahhhhhh, thanks

I just talk with a friend statical man and he give the same aswer that you batman.

The only issue is : if you use a gage for SPC chart you should be use a 6 sigma, if not use the regular calculation.

For what ? only the impact the readings and more exacly which error is permissible on this instrument.

thanks

 

[Batman]

Not sure of your question, Chuy, but when you perform a GR&R, you are qualifying the gage to either accept readings from it or not. SPC is separate from GR&R in that, given the gage is acceptable, the actual readings from the process are charted, and any other [correct] data analysis is accepted since the data were collected and accepted by an acceptable gage.

 

[AllenLee]

G R&R

I have a silly question, does the G R&R mean 5.15¦Òm ( Standard deviation of measurement system)?

Thanks!

Allen

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Allen Lee

 

[Ken K.]

A gage R&R is a method of evaluating several potential sources of variation in a measurement system. The typical gage R&R quantifies the variation due to differences between parts, between operators, and between units treated identically (gage variation).

The idea is that the variation between operators and the gage variation should be small compared to the total variation observed. If it is not, you can use the gage R&R to determine whether you need to retrain your operators or improve your gage, or both.

If you haven't already, I strongly suggest you purchase a copy of the AIAG Measurement System Analysis Reference Manual, available at http://www.aiag.org/

Only $11 for non-members. It is well written.

I also strongly suggest you invest in statistical software capable of analyzing the results properly. Your best bets are MINITAB, StatGraphics, and JMP. I prefer MINITAB.

Ken K.

 

[Rick Goodson]

Ken,

You opened the door for another question. Why do you prefer Minitab over StatGraphics or JMP?Regards,

Rick

 

[AllenLee]

Thanks for your response. But my question is whether the G R&R is the 90% of the measurement system distribution (5.15 sigma of measurement system). For I see, in the formula calculating EV and AV, it includes the constent index 5.15, am I right?

Thanks!

Allen

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Allen Lee