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Burunduk said:In the first example, basic ø3 defines the size of the cylinder, but not its location. The location of the cylinder is defined by 2.4 and 2.375.
In the second example dimensioned as in the second version by 2.4, 2.375 and R1.5, all three basic dimensions combine to define the arc's location relative to the origin of the datum reference frame, including the radius.
Burunduk said:Here is a question - if a radius of 20° arc floats in space relative to its original placement but keeps its value (for example R1.5), do we say it dislocates/translates? I suppose the answer is yes.
If the same radius remains concentric to its original placement but changes the radius value (progresses) do we no longer say it dislocates/translates?
pmarc said:OK, in that case it seems like in your opinion the arrangement of basic dimensions does in fact matter.
pmarc said:I will answer by just saying that I fully agree with Evan that it is not worth spending time on figuring out the meaning of all these different terms
Evan said:If the arc floats in space but keeps the same radius, I would say that it has translated. If the arc keeps the same center but changes radius, it has progressed and not translated
ASME Y14.5-2018 said:3.32 FEATURE AXIS
feature axis: the axis of the unrelated AME of a feature.
3.33 FEATURE, CENTER PLANE OF
feature, center plane of: the center plane of the unrelated AME of a feature.
5.9.6 Effect of LMC
[...]
5.9.6.2 Explanation of the Axis Method. When an orientation or position tolerance is applied on an LMC basis, the feature’s axis, center plane, or center point shall not violate the tolerance zone. The tolerance available is the specified value if the unrelated actual minimum material envelope is at the LMC limit of size. When the size of the unrelated actual minimum material envelope of the feature departs from LMC, the tolerance zone increases. The increase in the tolerance zone is equal to the difference between the specified LMC limit of size and the unrelated actual minimum material envelope size. The resulting tolerance zone is equal to the stated geometric tolerance plus the additional tolerance. See Figures 10-15 and 10-17. The total permissible variation for the specified geometric characteristic is maximum when the unrelated actual minimum material envelope of the feature is at MMC, unless a maximum (“MAX”) is specified in the feature control frame.
Yes, this is exactly how I interpret the axis control definition of an LMC tolerance in Y14.5. If recall correctly, the corresponding definition in the new Y14.45 standard on measurement data reporting is different because the "measured" versions of the feature axis and feature center plane changed relative to Y14.5 to be able to be produced from the "minimum material" envelopes for LMC-modified tolerances, so that the controlled element and the size considered for the bonus tolerance are to be determined from the same envelope depending on the material condition in which the tolerance applies. This is nice and makes sense functionally, but now there is a discrepancy between the standards. I could understand the logic of sticking with just the Unrelated AME, had the size used for the bonus calculation also been determined from it. It could allow inspection with pin gages. But I do understand your warning from relying on terminology too much.pmarc said:So in the light of this, should we now understand that for the axis method of tolerances at LMC one must find the UAME axis or center plane as the feature that needs to fall inside the tolerance zone, but at the same one must calculate bonus tolerance based on the UAMME size?
I look for the answers in the terminology in the text, because it is counterintuitive for me that a feature of size (closed shape) and a feature without opposed points are treated the same when it comes to the expectation from the tolerance zone to "progress" per the dynamic profile concept. Why counterintuitive? Look again in my last sketch. If the R1.5 arc on the top of both the left side and the right side is the 'before' version, then what should make me think that the process that caused the 'after' result should be called 'translation' on the right side, and on the left side 'translation' did not occur? It makes more sense that if both arcs shifted in the negative direction of the vertical axis, they both utilized a translational degree of freedom, in other words they both translated, even if in one case the arc remained concentric to its original version and changed its radius value, and in the other case it remained with fixed curvature and simply moved as it is.pmarc said:You hold very tightly to the terminology in this case.
In simple words, translation in geometry is when some geometric element moves from one place to another. You can detect it by the change in linear distance from a known reference. In tolerancing, the term is related to variation in location.3DDave said:how do you define the word "translation" in the context of geometric discussions?
3DDave said:Thanks for Googling that answer for me.
It appears to answer your previous question about translation concerning a solid definition.
Progression for a small angle arc can be viewed as a combination of translation and deformation (change of curvature).Evan said:I suppose that my point is that the progression concept ends up being a simpler way to describe what happens in a variety of cases.
ASME Y14.5-2018 said:When the dynamic profile tolerance modifier is applied in a segment of multiple single-segment feature control frames and includes datum feature references, the tolerance zone is constrained in translation and rotation, but not size, as applicable
"The datum feature references in any segment are not permitted to be an exact repeat of all the datum feature references in other segments. Each complete horizontal segment may be verified separately."ASME Y14.5-2018 said:10.5.2 Multiple Single-Segment Positional Tolerancing
For multiple single-segment profile tolerancing, datum feature references are interpreted the same as for multiple single-segment positional tolerancing. See para. 10.5.2.ASME Y14.5-2018 said:11.7 MULTIPLE SINGLE-SEGMENT PROFILE TOLERANCING
ASME Y14.5-2018 10.5.2 said:Each complete horizontal segment may be verified separately