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This topic contains 4 replies, has 4 voices, and was last updated by John Wick 2 weeks ago.

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- October 26, 2018 at 5:35 am #707353
So i have encountered that in some applications we do not pass the Gage R&R.

In some cases when the process or the customer tolerances are not to strict.sometimes you can be at USL or LSL and even to be outside the Limit Specifications and is not the end of the world, you just keep adjusting. Also lets imagine you can not improve the method anymore, because you need another technology and is so expensive that Upper Mgt will not want to invest.

I have experience a couple of time, specially with destructive testing, and special process like Foam Injection.

I want to hear What have you done on this cases, what recommendations can you make, and your experience about this.

Is Much appreciated.

October 26, 2018 at 7:25 am #707354@johnwick You can take multiple measurements and average them. Somehow I have a feeling that is what you wanted someone to say. It is a method that is pretty well known.

October 29, 2018 at 6:39 am #707370@Mike-Carnell , Not really i was not expecting any particular answer just to shoot some ideas,

But thanks that is one way to do it. i can use this for future references.In those cases im talking about, average the results will not pass the Gage R&R though.

October 29, 2018 at 7:46 am #707372@johnwick the method Mike referenced is often called Signal Averaging. It relies on the Central Limit Theorem which says that the standard deviation of sample averages is smaller than the standard deviation of individual measurements by a factor of the square root of the sample size. Therefore the distribution of averages of 4 measurements will have half the standard deviation of the distribution of individual measurements (the square root of 4 is 2). So if you know how much you need to reduce the measurement variation, you can calculate the number of measurements you need to average to pass the Gage R&R. The downside is taking multiple measurements and averaging them becomes your new measurement system.

On the other hand, if the tolerances are not very strict as you say, you may already have good P/T (Precision to Tolerance), but poor P/TV (Precision to Total Variation). If you have both good P/T and good process capability, then I would not worry about poor P/TV.

October 29, 2018 at 4:28 pm #707377@jazzchuck Makes total sense, i will definitely try it.

you are right about this: The downside is taking multiple measurements and averaging them becomes your new measurement system.

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