Different profile tolerance at each end of plate

[bxbzq]

Hi,
Details see attached. I use the idea of fig. 7-27 in '09 std on profile. Does it make sense to you? The larger profile tolerance on surface B is mainly because of process variation but functionally it is acceptable.

 

[CheckerHater]

I understood what you are trying to achieve without problem, but I agree it looks unusual.

It appears like you essentially trying to control the edges of the part (Side surface at bottom flat surface = edge between side and bottom)
Did you consider using Profile of a line instead? Profile of a line will apply to horizontal “slices” and requirement that slices on top are controlled looser than on bottom makes sense.

Just an idea.

 

[bxbzq]

CheckerHater,
How do I specify those incremental sliced tolerance zones along the height using Profile of a line?

 

[CheckerHater]

I am not sure.
In your example, how do you specify where “A” tolerance zone ends and “B” tolerance zone starts?
Are you actually trying to control something different like taper?

 

[Belanger]

Fig 7-27 is a guide for how this tapering idea works. This profile example is an interesting extension of principles.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[CheckerHater]

I would say it’s “two-step” extension: first, we stretch from position controlling axis to position controlling boundary, then from position to profile.

Like I said, I understood the idea, it just wasn’t clear to me, are we trying to control the area where side meets the flat AKA “edge”, or trying to create tapered tolerance zone.
So, maybe we are extending the principles too little too far.

I am really interested what others have to say.

 

[bxbzq]

Tolerance zone see attached.

 

[greenimi]

Why we cannot use all around (not all over) profile (for size and form) with position with Boundary for location/orientation for the upper surface and the same thing (all around profile + position with Boundary) for the lower surface, with basic draft angle showing draft’s direction?

 

[CheckerHater]

Tolerance zone see attached.

I would agree that this extension of principle is “interesting”, but I am not sure it can be universally understood to be considered “unambiguous”.

Technically, it violates mathematical definition of profile tolerance zone.
At least, “conical position” has a couple of pages dedicated to it in ASME Y14.5.1M, where it is being explained to the finest detail.

 

[bxbzq]

CheckerHater,
How does it violate the mathematical definition of profile tolerance zone? I don't have ASME Y14.5.1M in front of me.

 

[Belanger]

The tangent plane modifier on profile would also probably "violate" Y14.5.1, yet I've seen that attempted on a profile tolerance wrt datums.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[CheckerHater]

Bxbzq:
According to ASME Y14.5.1M “A profile tolerance zone is an area or a volume generated by offsetting each point on the nominal surface in a direction normal to the nominal surface at that point”.
ASME Y14.5.1M also has entire Chapter 5.4 CONICAL TOLERANCE ZONE dedicated to position.
Belanger:
Well, use of tangent modifier with datum-related characteristics other then orientation is “explicitly encouraged” (if it’s possible) in Para 6.5, for better or for worse. It is also understood, that tangent requirement overrides tolerance zone it applied to.
When somebody uses tangent with run-out, then it will be really disturbing.

 

[axym]

Hi All,

If this type of tapered tolerance zone is intended, I would recommend using the non-uniform profile method described in Section 8.3.2 of Y14.5-2009. The tolerance zone would be annotated with basic dimensions. I would not recommend trying to adapt the conical position tolerance zone concept for use with profile.

Non-uniform profile is a new tool in the Y14.5-2009 standard. The Y14.5.1M-1994 mathematical definitions standard was based on Y14.5M-1994, and thus did not deal with non-uniform profile. The next version of Y14.5.1 will address it.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[CheckerHater]

Axym,

You beat me to it while I was making nice picture

 

[greenimi]

Sorry to be persuasive, but what *IS* wrong with my proposal:

"Why we cannot use all around (not all over) profile (for size and form) with position with Boundary for location/orientation for the upper surface and the same thing (all around profile + position with Boundary) for the lower surface, with basic draft angle showing draft’s direction?"

Why this does not work?
I am NOT implying it does. I am asking.

Thank you for your input

 

[pmarc]

I agree that non-uniform profile tolerance is better choice. However I have two caveats to CH's graphic (sorry CH):

1. Minor thing - the leader of profile feature control frame should touch true profile of the part, not the contour of non-uniform profile tolerance zone (see figs. 8-9 through 8-11 in Y14.5-2009).
2. Bigger issue - since the height of the part on bxbzq's original drawing is directly toleranced, height of the profile tolerance zone shown on CH's picture may vary from 25.0 to 25.2 depending on the actual height of the part. In my opinion, since it was decided not to apply the principle shown in fig. 7-27 in this case, the unique height of the profile tolerance zone can't be clearly determined. This in turn means that we may get different profile tolerance zone shapes (with different included angles) depending on the height of the part. In order to eliminate this ambiguity I would suggest adding basic height dimension to the detail view, for instance basic 25.2. Unless bxbzq is fully comfortable with this changing included angle depending on the height of the part.

 

[CheckerHater]

You forgot to mention that I should use phantom line instead of center line.

 

[pmarc]

Correct

 

[bxbzq]

Wait, where is datum A? The profile tolerance zone has nothing to do with datum A?

 

[pmarc]

That would be another caveat to the graphic and to my post