Question-Barrentine book: Concepts for GR&R Studies

K

KMAAA

#1
I'm somewhat new to GR&R studies though the statisitcs involved are very familiar.

Barrentine suggests in his book "Concepts for Gage R&R Studies" that doing the GRR & subsequently the Measurement Capability Index vs the process variation rather than the product tolerance(specs) is a better approach. Seems like a reasonable approach to me. However, there is something in his "sample procedure" on page 7 that doesn't make sense.

For those that don't happen to have a copy of the book in front of them:

>(In a sample R&R study calculation) He states his "Process Sigma" as = 50

>In the sample R&R study calculation he determines a sigma(R&R) of 11.4.

>Next he determines his Measurement Capability Index(MCI) as the sigma(R&R)/Process Sigma or [ 11.4/50 ] * 100 = 22.8%

This is where it doesn't make sense:

>If one were to use the traditional GRR approach of determining the MCI vs the tolerance(specs) then the MCI above would be MCI = [ 11.4/ (USL - LSL) ] * 100

>If one were to use the newer GRR approach of using the process variation then, it seems to me, that one would use an MCI calculation of {[ 11.4/ (UCL-LCL) ] * 100} not the "Process Sigma" he's stated as 50 or MCI = [ 11.4/50 ] * 100.

>If you've transitioned from the older traditional [GRR vs the tolerance] to the [GRR vs the Process Sigma(as Barrentine states)] NOT [GRR vs UCL-LCL] then I would think a successful GRR result would become MUCH more difficult & have less meaning in the long run.

What am I missing here? Is Barrentine's "Process Sigma" of 50 actually (6*sigma)?
 
Elsmar Forum Sponsor

Atul Khandekar

Quite Involved in Discussions
#2
KMAAA said:
This is where it doesn't make sense:

>If one were to use the traditional GRR approach of determining the MCI vs the tolerance(specs) then the MCI above would be MCI = [ 11.4/ (USL - LSL) ] * 100

>If one were to use the newer GRR approach of using the process variation then, it seems to me, that one would use an MCI calculation of {[ 11.4/ (UCL-LCL) ] * 100} not the "Process Sigma" he's stated as 50 or MCI = [ 11.4/50 ] * 100.

>If you've transitioned from the older traditional [GRR vs the tolerance] to the [GRR vs the Process Sigma(as Barrentine states)] NOT [GRR vs UCL-LCL] then I would think a successful GRR result would become MUCH more difficult & have less meaning in the long run.

What am I missing here? Is Barrentine's "Process Sigma" of 50 actually (6*sigma)?
KMAAA,

Welcome to the Cove Forums.

Measurement Capability Index MCI_1 based on Process Variation is defined as:
MCI_1 = 100 (Sigma_GRR/Sigma_process)

The other index, based on tolerance is:
MCI_2=100(5.15 * Sigma_GRR/(USL-LSL) )
On place of 5.15 you can also use 6 to cover 99.73% spread).

Barrentine's calculations:
- K factor used are from MSA edition 2, ie. they are already multiplied by 5.15.
- To calculate GRR variation, he divides by 5.15 , ie. resulting value is 1 Sigma_GRR =11.4
- So MCI_1 is calculated using 1 Sigma values for GRR and Process Variation.
The value of 50 is 1*Sigma value.

If we were to use the 'traditional' approach,
MCI_2 = [ 5.15* 11.4/ (USL - LSL) ] * 100


Hope this helps.

- Atul.
 
K

KMAAA

#3
aah..

...And that was exactly what I was missing. Your remarks clear everything up...the world has regained order.

Thanks for having this forum available. I just became aware of it as I was searching for the answer to my question(confusion). I'll try to add as much as I ask...if possible.

thanks, & take care,
Kevin
 
Thread starter Similar threads Forum Replies Date
M Question for Auditors - "Off the Record" Conversation? General Auditing Discussions 14
D Question regarding ECO process, specifically for Life Science products and defining form fit and function ISO 13485:2016 - Medical Device Quality Management Systems 1
R Accelerated Aging - Creating test samples - Implantable medical device Question Other Medical Device Related Standards 4
A Question on Authorized Representative in Malaysia Other Medical Device Regulations World-Wide 1
D Limited Scope for second site Question? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 5
I ISO 2233:2000 Question - Medical Device Shipping/Transportation Validation Other ISO and International Standards and European Regulations 1
Anonymous16-2 Labeling Question (Dietary Supplements/Food) Pharmaceuticals (21 CFR Part 210, 21 CFR Part 211 and related Regulations) 1
T Question for: Cg & Cgk calculation General Measurement Device and Calibration Topics 3
N ASL Question for GitHub ISO 13485:2016 - Medical Device Quality Management Systems 6
hogheavenfarm GDT Flatness measurement question Inspection, Prints (Drawings), Testing, Sampling and Related Topics 10
A Question on ISO 14001:2015 - Are annual audits required? ISO 14001:2015 Specific Discussions 8
dinaroxentool Question about FDA Classification of a Device 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 3
J Another DFAR question 252.225-7009 AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 0
F Conflict Mineral Smelter Question RoHS, REACH, ELV, IMDS and Restricted Substances 8
R NRTL - Scope Question - Off-the-Shelf Plug In IEC 60601 - Medical Electrical Equipment Safety Standards Series 0
D API 6A Certification Question Oil and Gas Industry Standards and Regulations 4
dinaroxentool Question about qualification as a medical device or accessory in Europe EU Medical Device Regulations 2
R DHR question: Traceability of components ISO 13485:2016 - Medical Device Quality Management Systems 2
C MDR - Question around software accesories EU Medical Device Regulations 2
K My question is, what/when is a nonconformity? Therefore what requires an NCR? Nonconformance and Corrective Action 9
Watchcat Authoritative References about the Research Question? Quality Tools, Improvement and Analysis 0
T Question about Quality Department employee position titles Quality Manager and Management Related Issues 10
N Question on creepage/clearance requirements for HF Active Accessories for 2nd edition 60601-1 IEC 60601 - Medical Electrical Equipment Safety Standards Series 1
I Question 1 - Nitpicking on Document Approval - can a document approval record be separate? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 6
J Question: How to create an IMDS RoHS, REACH, ELV, IMDS and Restricted Substances 3
K Question on whether IEC 60601-2-62 standard is applied IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
B QMS question in regards to multiple medical devices/products and N/A activities Other Medical Device Related Standards 12
C NB approval - Basic question about Notified Bodies and their role EU Medical Device Regulations 10
G Question about Non-conformances during New Product Introduction Nonconformance and Corrective Action 14
F ISO 13485 8.2.3 Reporting to regulatory authorities: Question regarding a procedure for this clause. ISO 13485:2016 - Medical Device Quality Management Systems 4
O Mitutoyo Digital Caliper to PC USB question General Measurement Device and Calibration Topics 2
R Probability - Need a help to solve the below question Statistical Analysis Tools, Techniques and SPC 5
B Minitab Type 1 Gage Study on True Position Question Measurement Uncertainty (MU) 1
Q Supplier audit question cataloque VDA Standards - Germany's Automotive Standards 0
Ed Panek Inactive key supplier question - We are not actively buying from them ISO 13485:2016 - Medical Device Quality Management Systems 2
T Potential Off-Label Use question 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 5
R Question on determining defective units - I am not recording fixture to part rejected Statistical Analysis Tools, Techniques and SPC 5
Ed Panek Rule 11 Question - CE approvals for software as well as the medical device EU Medical Device Regulations 6
H Question about implications of performing Firmware upgrade via MDDS - Medical Device Data Systems 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 2
D Company Moving - Relabelling Question Medical Device and FDA Regulations and Standards News 0
Ronen E Tolerance intervals (?) question - Flow Rate Probability Range Statistical Analysis Tools, Techniques and SPC 6
S Conformity Assessment Route question for Class IIa medical device under MDR EU Medical Device Regulations 3
K AS9100D 8.4.1.1 external providers question - Walmart, Home Depot, our lawn care team. etc. AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 20
E Question on GD&T added to print - Positional callout for the small holes Inspection, Prints (Drawings), Testing, Sampling and Related Topics 3
J IEC 60601-1, ed 3.1 - Blue icon question IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
A PFMEA English language question IATF 16949 - Automotive Quality Systems Standard 4
D GD&T Drawing Question - I have a drawing and it makes no sense to me whatsoever Inspection, Prints (Drawings), Testing, Sampling and Related Topics 7
D Yet another torque question... Assembly processes AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 2
A A Question about Continual improvement process in AS9100 AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 4
S Question about a basic additive variance/tolerance example Quality Tools, Improvement and Analysis 2

Similar threads

Top Bottom