Intro to MSA of Continuous Data - Part 10: Creating gauge families
Posted 18th March 2010 at 10:57 PM by Miner
Related Topic Tags measurement system analysis, msa
This is the tenth in a series of articles about MSA. The focus of this article will be on minimizing the number of MSA studies by creating families of gauges.
A frequent question in the Cove is: “Must I perform an MSA on every gauge/part combination?” The answer is: “No. You may create families of gauges, and perform MSA studies by family.”
Wait! Not so fast! What constitutes a family of gauges? Well, there are certain criteria that must be met:
Same/similar gauges:
Conservative approach: Same brand and model of gauge
Alternate approach: Similar gauges (brand or model not relevant)
Conservative approach: Same features
Alternate approach: Similar features (e.g., diameter, width, step etc.) within a specified range. Be cautious when establishing the range. You may need to perform a series of MSAs to establish how large this range may be. The impact of size will usually manifest itself through changes in the within-part variation, or by affecting the ease with which an operator can handle the part and gauge together.
Same tolerances or process variation:
Conservative approach:
Once you have created a gauge family, document it. Create a record for each gauge family that clearly describes the gauges, characteristic and size range. The gauges could be identified by listing all serial numbers, gauge calibration ID numbers, or by clearly specifying the type, range, display, resolution and anvils.
Perform the MSA and associate it with the gauge family record.
A frequent question in the Cove is: “Must I perform an MSA on every gauge/part combination?” The answer is: “No. You may create families of gauges, and perform MSA studies by family.”
Wait! Not so fast! What constitutes a family of gauges? Well, there are certain criteria that must be met:
- Same gauges
- Same product characteristics
- Same tolerances or process variation depending on use of gauge
- Similar gauges
- Similar product characteristics
- State the smallest tolerance or process variation (standard deviation) that the gage family may be used to measure and still achieve an acceptable R&R result
Same/similar gauges:
Conservative approach: Same brand and model of gauge
Alternate approach: Similar gauges (brand or model not relevant)
- Same type (e.g., calipers, micrometers, 3 – point bore gage, etc.);
- Same range (e.g., 0 – 6 inch, 0 – 12 inch, etc);
- Same display (e.g., digital, dial, vernier, etc.);
- Same resolution (e.g., 0.0001, 0.05, etc.)
- Same technology, if relevant (e.g., scaled, rack and pinion gear, electrostatic capacitance technologies for calipers)
- Same anvils, if relevant (e.g., outside, inside, step anvils for calipers)
Conservative approach: Same features
Alternate approach: Similar features (e.g., diameter, width, step etc.) within a specified range. Be cautious when establishing the range. You may need to perform a series of MSAs to establish how large this range may be. The impact of size will usually manifest itself through changes in the within-part variation, or by affecting the ease with which an operator can handle the part and gauge together.
Same tolerances or process variation:
Conservative approach:
- Same tolerance if gauges are used for inspection
- Same process variation if gauges are used for SPC
- If gauges are used for inspection, state the smallest tolerance at which an acceptable % Tolerance may still be achieved
- If gauges are used for SPC, state the smallest process variation standard deviation at which an acceptable % Study Variation may still be achieved
Once you have created a gauge family, document it. Create a record for each gauge family that clearly describes the gauges, characteristic and size range. The gauges could be identified by listing all serial numbers, gauge calibration ID numbers, or by clearly specifying the type, range, display, resolution and anvils.
Perform the MSA and associate it with the gauge family record.
Total Comments 4
Comments
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Excellent! This can help me a lot.Posted 19th March 2010 at 03:31 AM by Mgrace 
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I hope you have read the whole series of Miner's blog entries. They are excellent!Posted 22nd April 2010 at 08:19 PM by Marc 
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Tks Miner !Posted 17th July 2012 at 09:21 PM by Berg.Jlle
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Could I please get some help trying to understand our customer needs. they asked for a gage R and R. We gave it to them. they are o.k. with the 16.16 %R&R but not the 89.27 % apprasier variation.
% process var. % tolerance var.
% Equipmeny variation 32.82 5.58
% Appraiser variation 89.27 15.17
% R & R 95.11 16.16
% Part variation 30.88 5.25
I will be the 1st to admit I do not know how to read these results can anyone enlighten me?Posted 11th September 2012 at 04:16 PM by Dean Frederickson
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