CMM Reports and Rounding...

[[Ja...]]

This is my first post in the Zeiss forum so bear with me if this has already been answered.

 

I have been asked to look into reformatting the report generated from the CMM to see if there was a way to change how CALYPSO makes its judgement on the report.

Our report currently generates measurements out to the 6th decimal place (.XXXXXX) and makes a red/green judgement accordingly.

 

As much as I disagree, the task is to reduce the measured value to one decimal place past the part tolerance and judge based off this value.

I.e., if a part specification is 2.000 +/- .010 and the part measures 2.010040, the wish is for the CMM report to show 2.0100 and a green judgement. 

 

As I stated, I do not agree with this methodology because it is not in accordance with Section 5.4 of ASME Y14.5-2018.

 

I'm also learning how CALYPSO and PiWeb tie together so I'm not sure if this is something that can easily be done in PiWeb or vise-versa.

 

I appreciate any feedback to this.

 

 

[[Lu...]]

Here is a post from last year, may be of some help
 

 

Edited Thursday at 03:36 PM

[[Je...]]

Hi

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Thanks for creating your first post, and I look forward to reading many more from you.

I think the scenario you presented about rounding and significant digits is one that many of us have encountered.  So, yes, it has been discussed on these forums, but by no means is it "answered."  It's an ongoing discussion.

Luke's reference to a similar post is helpful.

My stance:
------------

The associates who are encouraging you to show "green" on the report when a numerical size limit has been exceeded (which is effectively what they are asking for) should reconsider their request.

They are not asking for truncation to significant digits.  They are requesting you to round.  True metrology software should guard against this behavior, and I'm grateful that Calypso does exactly that.

In any situation in my professional career when this has been requested, I have informed the person making the request that they are welcome to make the proposed alterations with their own ink and signature.  I will not.

[[Ri...]]

My favorite argument that I heard for the rounding was that the CMM was too accurate. 🤣

[[Ja...]]

Thank you all for the feedback and this is even more ammunition I need to help push back.

My inspector and I dug into CALYPSO earlier this morning investigating this and we both agreed that doing this is completely not a good idea.

It goes against the very standard that our drawings are built around. 

 

The Y14.5 is black and white, plain and simple. 

All values are absolute, regardless of how many decimal points are reported and measured.

[[Ch...]]

I agree with the gentlemen above, the only potential argument against this is :

What is the 'actual' uncertainty of the machine, which is a long an drawn out process to truly calculate, in which case sure there could be some wiggle room - however it also could potentially be worse than reported - which then perhaps guard banding may be required, etc.

The other great cases for this situation are (😉) :

a) What is .0001 between friends ? 😁🤣

b) .0001 - that will be gone as soon as they fire up the chopper 😁😂

Welcome to the world of measuring.