MSA (Measurement System Analysis) - Dimension Selection

C

ckgindia

1. If drawing specified dimension is 25.00 +/- 0.10 mm, may i choose for Gage R&R value selection to 70.00 and do the tests. Is it feasible for right Gauge R&R?
2. If Yes or No what would be right values (Ranging "From", "To" - From mean value of drawing specification)?

Please Help. Thanks.
 
Last edited by a moderator:

Ron Rompen

Trusted Information Resource
Re: MSA - Dimension Selection

To truly represent the capability of the measuring device being evaluated, the GR&R should be produced on parts which:
i) have the feature in question
ii) represent the range of expected variation in the product

In other words, use parts which range from approximately 24.90 to 25.10, with (if available) a few parts which exceed these limits.
 
C

ckgindia

Re: MSA - Dimension Selection

To truly represent the capability of the measuring device being evaluated, the GR&R should be produced on parts which:
i) have the feature in question
ii) represent the range of expected variation in the product

In other words, use parts which range from approximately 24.90 to 25.10, with (if available) a few parts which exceed these limits.
Hello Rompen - Thanks to your response.
 
C

ckgindia

Re: MSA - Dimension Selection

Hello Miner - I'm getting this error message while visiting your forum "An Invalid Blog is specified in the link you clicked on. The thread or post has been permanently deleted. Please try a Search or PM a forum Moderator or Contact us if you need help"

Thanks.
 

Miner

Forum Moderator
Leader
Admin
I check the link on my end and it is working. If you are accessing from a business, they may be blocking access to a blog. I have copied the relevant paragraph below.

Part Selection

The first step in an effective R&R study is to determine the use of the gage itself. Will it be used for part inspection to a tolerance, for process control, for statistical studies (e.g., a hypothesis test, capability study, DOE, etc.), or for a combination of these? This is very important because it influences the selection and quantity of parts needed for the R&R study.

If the gage is used solely for part inspection, the selection of parts is not critical because the part variation is not included in the calculation of the R&R metric, %Tolerance (i.e., P/T Ratio). Some will recommend that parts representing the full spread of the tolerance be used. While this does not hurt, it is not really necessary. If a gage linearity study has been performed, the change in bias over the tolerance spread is known. If a gage linearity study has not been performed and there is a linearity issue an R&R study will not detect it.

If the gage is used for part inspection or for statistical tests, the selection of parts is critical because the part variation is part of the calculation of the R&R metric, % Study Variation (i.e., %GRR). It is vital that the parts selected for the study reflect the actual variation of the process. That is, the StdDev of the parts equals the StdDev of the process. Some statistical packages, such as Minitab, allow the entry of the historical StdDev of the process. If your software has this option, use it, entering the process StdDev from a capability study or calculated from SPC charts. If the software does not have the feature, manual calculations using the historical value are still possible as follows"

% Study Variation = 100 * [StdDevR&R / StdDevTotal Variation]

StdDevTotal Variation = SQRT[StdDevR&R^2 + StdDevPart Variation^2]

Manually substitute the StdDev from a capability study for StdDevPart Variation
 
Top Bottom