Gage R&R - Sampling rule and process range

P

Palt88

#1
Hello all, :bigwave:

I done gage since years, but I realize that even recently I have done some without really understanding the things, and probably it was not done the best way. I’m still learning things as any situation is different from others. I think the force of a forum is to compile real experience, investigation, interpretation, that’s why I want to discuss with you about this topic as its part of my current activity.

I passed though the 35 pages of threads regarding Gage R&R, and particularly about rule to apply for the choice of nb of operator, nb of pcs, nb of replicates. As readed it seems there’s no strict rule for that…ok let’s say a minimum requirement…

I would share some knowledges and also ask some clarifications that I’m still looking for:

In my previous enterprise, a GRR sampling rule was written in the internal procedure:
- if the nb of pieces X number of operators is >15, then do 2 replicates
- if the nb of pieces X number of operators is within 8 and 15, then do 3 replicates
- if the nb of pieces X number of operators is within 5 and 8, then do 4 replicates
- if the nb of pieces X number of operators is <5, then do 5 replicates

Now in my current company here the rule of one customer:
- nb of operator X nb of replicates X nb of pieces > 60

:confused:

Question 1:
Did somebody knows or already saw this kind of rule in litterature or norms?
I got only MSA 3rd edition and see nothing like that in it so maybe I missed it somewhere?

Question 2:
Statements in the threads are that more pieces we have for executing the GRR, more we are confident in the results; however did someone already calculate what the confidence level of the basic rule is and how the confidence level is going if we increase the number of pieces?


As additional informations for the sampling:

- Minitab is able to generate Gage R&R study worksheet. However it follows no rule (a GRR combination of 1op X 2reps X 2pcs is possible for example). A guy from Minitab confirmed to me that there’s no rule for that in Minitab.
- Minitab has a Gage R&R sample size guidance in the help section, but in fact there’s no generic rule inside. Interesting advices are:
o “Use more parts with few measurements of each rather than few parts with many measurements of each”
o “Select parts that represent the actual or expected range of process variation”

Yes….the last sentence is very important and was discussed in other threads, and I assume that everybody knows that the “GRR% to process variation” is very sensitive to the selected pieces (as the “%GRR to Tolerance” is not).
As stated in the AIAG “For process control situations (…) the availability of samples over the entire range operating range becomes very important. An independent estimate of process variation (process capability study) is recommended when assessing the adequacy of the measurement system for process control.

Question 3:

Ok for the capability study, but the time range to be assessed for determining the process variation is still little bit confusing for me, I assume to know my process I have to do a long-term analysis (PpK) and not just taking a CpK of the day before…My approach is then to do an assessment of the process since january 2008, then pay attention that the sampling used for the Gage R&R is representative of the long-term process range (more or less of course).
Do you agree with this approach or do you have another proposition?

Question 4:
I believe that the quantity of pieces manufactured has no link with the quantity of pieces to be selected for executing a gage R&R (i.e the
For example the GRR sampling for assessing a measurement process thatmanufacturing of 30 million of component per year or 10000; the sampling for the GRR will be not different.
Did someone can just confirm that?


Thanks to all for any answers.
Fred
 
Elsmar Forum Sponsor
J

justncredible

#2
Q1. Each operator needs to trained in the use of the gage, and it does not hurt to do a study to make sure the AV% is within reason.

How else can you prove the training on the gage?

Q2. I think it is included in Miners GR&R excel sheets. It has a proformance curve.


Q3. I agree with that, and it says in the MSA 3rd ed to do timely studies based on gage use and process life.

Q4. As long as the process is proven stable and the parts used for the GR&R are from the expected process range.
 

Miner

Forum Moderator
Staff member
Admin
#3
Q1) I have seen similar guidelines before, but no established rule.

Q2) It is important to provide a balanced study. More parts may improve your confidence in the Part Variation, but if it is at the cost of fewer operators, you have less confidence in the Reproducibility. Balance among all three is important.

Q3) When you create an SPC chart, the limits and points plotted are based on the short term variation not the long term variation, so the parts selected or the capability used should also be the short term capability.

Q4) You are correct. You are after an estimate of the capability. The size of the population has no impact on the size of the confidence intervals around the mean and standard deviation. The sample size does affect the size of the confidence intervals.
 
P

Palt88

#4
Q3. I agree with that, and it says in the MSA 3rd ed to do timely studies based on gage use and process life.
Q3) When you create an SPC chart, the limits and points plotted are based on the short term variation not the long term variation, so the parts selected or the capability used should also be the short term capability.
Thanks both for your answers.

Miner, for the Q3 ok for the SPC, but in this case you will then have a "short term" GRR (you don't know if the short term variation is representative of the entire operating range of the usual process).
I'm saying that in the case of tool wear for example, you can have different variation during the year.
That's why I focus on long term behavior to have an accurate GRR%.
Also if more than 1 tool is used for the process (but not simultaneously) you have to span the correct timerange.
What do you think ?
 
Last edited by a moderator:

Miner

Forum Moderator
Staff member
Admin
#5
Thanks both for your answers.

Miner, for the Q3 ok for the SPC, but in this case you will then have a "short term" GRR (you don't know if the short term variation is representative of the entire operating range of the usual process).
I'm saying that in the case of tool wear for example, you can have different variation during the year.
That's why I focus on long term behavior to have an accurate GRR%.
Also if more than 1 tool is used for the process (but not simultaneously) you have to span the correct time range.
What do you think ?
This is true from the perspective of capability, but remember that when you are taking the measurements, you are making decisions about process control in real time. In real time, the only process variation is short term variation. This is the variation that your measurement device needs to be able to discern.
 

ugurkavi

Registered Visitor
#6
Q.1... Well, as others mentioned there are no specific rules.
Q.2... I don't believe when people say "the more samples you have the more accurate (or higher confidence) are the results". I usually perform a test to see what should be the optimum sample size. The latest version of Minitab has a similar function. By performing this test I realized in some processes sampling size of 10 would be enough, in some less than 10 would be enough and in some sampling size of 20 or more would be necessary. As miner said, the balance is important. So my suggestion is that you should look into ways to find out the optimum sampling size for your different measurement systems.... just my two cents :)
 
Thread starter Similar threads Forum Replies Date
T Destructive Tensile Test Sampling Gage R&R Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 9
B Sampling in GRR - Why do we need 10 samples to do a Gage R&R? Inspection, Prints (Drawings), Testing, Sampling and Related Topics 9
T Plug Gage Calibration Calibration and Metrology Software and Hardware 1
L Gage R&R TMV Acceptance Criteria Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 4
S MSA for attribute relation gage Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2
E Zero part to part variation - Gage R&R project Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 15
M Gage R&R and right way to measure Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 16
L Gage RandR on automated equipment. IATF 16949 - Automotive Quality Systems Standard 7
B Gage calibration frequency, ISO and IATF - What are the requirements Calibration Frequency (Interval) 3
D Difference between Test Method Validation and Gage R&R Qualification and Validation (including 21 CFR Part 11) 18
R Determining Uncertainty from Gage R&R Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1
C Correct Calibration Method for Dial Depth Gage General Measurement Device and Calibration Topics 6
C Gage Block Wringing General Measurement Device and Calibration Topics 3
B Gage R&R with NDC=1 Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 19
S Type 1 Gage R&R or something else? Reliability Analysis - Predictions, Testing and Standards 6
G Should I perform Gage R&R only at the beginning of a new project? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 6
V Thread Plug Gage Pitch GO Diameter out of spec AQL - Acceptable Quality Level 8
G Gage R&R - Where am I going wrong? Part of a FAIR submission (Aerospace) Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2
R Gage R&R Excel templates Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 3
K Gage R&R with more than 3 appraisers Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2
Anerol C Gage R&R Template AIAG 4th Edition IATF 16949 - Automotive Quality Systems Standard 3
T Attributes SPC study - Attributive control (Go gage) Statistical Analysis Tools, Techniques and SPC 5
S Capability or Gage R&R Study for Leak Tester? Reliability Analysis - Predictions, Testing and Standards 15
N % Tolerance - Type 1 study on the gages, then a gage R&R (ANOVA) Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 4
M Definitive answer on Type 1 vs Type 2 vs Type 3 Gage Study Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 0
V Gage Management and Gage R&R Software General Measurement Device and Calibration Topics 1
D Gage R&R Study on Load Cells - Large chemical blending tanks IATF 16949 - Automotive Quality Systems Standard 1
B Minitab Type 1 Gage Study on True Position Question Measurement Uncertainty (MU) 1
S Gage R&R on alloy Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 10
8 Need Help - Runout - Function Gage Inspection, Prints (Drawings), Testing, Sampling and Related Topics 7
L Gage R&R studies for identical Devices - Need to confirm the requirement to perform them Reliability Analysis - Predictions, Testing and Standards 2
G Stab Pin Size For Check Gage Inspection, Prints (Drawings), Testing, Sampling and Related Topics 3
E Functional Gage for TOP applied at RFS Design and Development of Products and Processes 5
F No reproducibility Error in Gage R&R? Reliability Analysis - Predictions, Testing and Standards 4
M Template for Attribute Gage R & R wanted Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 3
G Warning about Deltronic Gage Pins - The "Certification of Accuracy" document General Measurement Device and Calibration Topics 13
A Gage type 1 study on CMM Capability, Accuracy and Stability - Processes, Machines, etc. 2
Q Gage R&R for Instant Measurement Machine Manufacturing and Related Processes 6
M Gage R&R with large inter part variance - Torque Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 7
D Do we need normal data for gage r&r studies? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 5
D Do I need part variation while doing Destructive Variable Gage R&R MSA study Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 19
S Gage R&R Standard Deviations Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 6
J Informational Gage R&R: Swapping operators Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 5
S Gage R & R for large amount of inspections IATF 16949 - Automotive Quality Systems Standard 10
S Ring Gage Thermal Expansion General Measurement Device and Calibration Topics 4
L Gage R&R for test precision or uncertainty prediction? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2
S Minor diameter of threaded ring gage General Measurement Device and Calibration Topics 1
A Does Torque Gage Need Validation? Reliability Analysis - Predictions, Testing and Standards 4
J Ignoring a Failed Gage R&R and upcoming external audit IATF 16949 - Automotive Quality Systems Standard 22
R Scaling a Gage R&R - 2 holding fixtures each with 10 nests Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 7

Similar threads

Top Bottom