Y14.45 Measuremnt Data Reporting questions 1

[metrologic]

Hi Everyone,

A few years ago I believe someone from an ASME committee mentioned on this forum they were working on a measurement data reporting standard. I read through that draft standard that was available back then and took some mental notes. And that was that. --I didn't realize this actually became an official ASME standard and was published a couple years ago.

I'll be ordering a hard copy when I get back to the office, but I'm super curious...

In the draft standard, three measurement reporting methods A, B, and C were defined.
A)Method A was simply to report pass/fail, accept/reject, etc. No variable data here, more like does this sample part fit in the gauge, yes or no?

B)"Method B provides variable data for a measured value of a tolerance specification. The method B
reported value is the particular measured value that is used to determine conformance to the tolerance
specification."

C)"Method C provides variable, graphic, or other measured values as additional information characterizing
size, form, orientation, or location of the measured feature. The method C reported values shall be
determined as specified in suitable document, such as a measurement plan."

I'm curious about method B. Draft method B data reporting examples were provided for pretty much all of the Y14.5 GD&T characteristics, features of size, etc.
However, in section 9 for profile of a surface, there was this note:

"NOTE: This Section defines reporting methods for uniform profile of a surface. Nonuniform profile of a
surface can be reported using method A or method C, but no method B measured value exists for
nonuniform profile of a surface."

No method B measured value exists for nonuniform profiles? What became of this?

 

[greenimi]

Since this is a very specific question pertaining to the development of the Y14.45 standard, your best bet is to post it on the linkedin group called GD&T and GPS World

https://www.linkedin.com/groups/12448871/

There, and I am positive on that, you will get a very qualified answers from people with knowledge on your inquiry.

 

[axym]

metrologic,

I can take this one - I'm part of the Y14.45 subcommittee. The note you referenced is in the published Y14.45-2021 - we were not able to include a definition.

The Method B measured values in Y14.45 are based on concepts and definitions for actual values the Y14.5.1 Mathematical Definition of Dimensioning and Tolerancing Principles standard. There was no mathematical definition for an actual value for non-uniform profile provided in Y14.5.1-2019 either.

Non-uniform profile tolerances still represent a major problem for numerical evaluation, for a number of reasons. There is no single tolerance value that represents the thickness of the tolerance zone, and no number is specified in the feature control frame. So there is no real basis for defining a Method B single measured value.

Another way of describing a non-uniform profile tolerance is that there is a different tolerance for each point on the true profile. In principle, a tolerance value and a measured value could be defined for each point. However, reporting data for a representative subset of these points would be cumbersome at best. A further complication is that Y14.5 allows non-uniform profile zones to be defined as CAD entities and there is no requirement for the boundaries to be centered on the true profile. Some of us have tossed around the idea of applying the growth parameter g value concept to quantify non-uniform profile, but this has not been included in any of the published standards.

Suffice to say that further study is still necessary. It may turn out that non-uniform profile zones are just too complex (or perhaps too abstract) to be represented by a single measured value.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[metrologic]

Hi axym, thanks for responding.

My apologies, I was mentally thinking that non-uniform profile was an unequal bilateral profile. My initial question is garbley-gook . But your reply jogged my memory.

So for an equal bilateral profile: method B is to be the growth parameter g method.
And for an *unequal* profile: method B is still the growth parameter g method???

That was actually my concern, are unequal profiles still reported with the growth parameter g method? (I understand non-uniform profiles are a different animal.)

 

[axym]

metrologic,

I'll try to clarify how the different dispositions are treated.

The growth parameter g method can be used to calculate a Method B measured value for any uniform disposition (equally disposed, unequally disposed, unilateral). The A = T + 2g formula applies.

For equally disposed (equal bilateral) profile tolerances, there is a simpler method that will get the same result. Double the largest absolute deviation from the true profile, and this should get the same result as the A = T + 2g formula.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[metrologic]

axym,

I hope I'm not bothering you too much with these details...

You mentioned Method B measured values in Y14.45 are based on concepts and definitions for actual values in the Y14.5.1 Mathematical Definition of Dimensioning and Tolerancing Principles standard.

In Y14.5.1M-1994, Sec6.5 PROFILE CONTROL...
"(c) Actual value. For both unilateral and bilateral profile tolerances two actual values are necessarily calculated: one for surface variations in the positive direction and one for the negative direction. For each direction, the actual value of profile is the smallest intermediate tolerance to which the surface conforms. Note that no single actual value may be calculated for comparison to the tolerance value in the feature control frame, except in the case of unilateral profile tolerances."

Could you comment on how the actual values defined in Sec6.5(c) relate to the new 14.45 Method B values? I always read Sec6.5(c) as indicating that I should probably supply two values on my dimensional reports for profiles, one for surface variations in the positive direction and another one for the negative direction. Are such positive and negative deviation pairs now considered Method C data?

 

[axym]

metrologic,

There is a more recent version, Y14.5.1-2019. The profile section was completely rewritten, and the actual value is now a zone-based single value that can be compared to the tolerance value. The growth parameter g concept is defined, and there are several multi-feature examples. The Method B measured value definitions in Y14.45-2021 are based on this new section. The deviation-based two-value definition from Y14.5.1M-1994 is now a former practice. These deviations can be reported as Method C data.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[metrologic]

Thanks axym!!!

Does the Y14.45 committee need anymore people? Does one need any special qualification to join such a group? I think I would love to participate in something like this!

 

[axym]

metrologic,

We're always looking for people from industry who are knowledgeable and interested. You can email me directly at the address below.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca