Profile of a Line per Y14.5-Next

Peter:

I like it but I hope that this is another example of profile of a line and not the complete definition. We still need a profile of a line application on stamping contours where they are confirmed with a template showing inner and outer boundaries.

Also there is a need for profile of a line on continuous product such as door seals. These are coiled product and one sections a thin perpendicular slice and confirms the profile of a line using an optical comparitor.

Dave D.

I can see that my example is incomplete.

I certainly understand that stamping contours and door seal cross sections need to be checked in some manner, but the Y14.5 Standard immediately starts to describe space in three dimensions. It seems that it might be good if Y14.5-Next specifically restricts the scope to 3-D. It seems as though stamping contours and door seal inspectors are trying to take 3-D objects and describe them in a 2-D world. Folks measuring such objects certinly need methodology, but I wonder if the Y14.5 Standard is marginalized by trying to include too much. (Perhaps I wander as I wonder too much.)

Peter Truitt
Minnesota

Looks like a bit of inconvenience to create the line first and only then apply control to the line.

Does anyone see this thing going the way of Symmetry and Concentricity?

CheckerHater:

I hope it doesn't go away or is unused such as concentricity and symmetry. It both those situations, we have another symbol or geometric application that can replace it such as positional or either runouts for concentricity. Symmetry would be replaced quite nicely with positional in RFS. Actually, MMC is even better.

Let's say we have a roll of soft spaghetti that has a contour that is somewhat shaped as a "G". We want to control the contour. At the present time, we would use profile of a line and take a thin slice. I don't know of another geometrical application that could replace profile of a line. Certainly, profile of a surface would not do it. Can you think of anything?

Dave D.

Profile of a surface applied on a "Unit basis" (incrementally) can and should, in my opinion, replace profile of a line. We would all be better off.

Dean

It might make sense to convert profile of a line into something just like what Peter is proposing... Let an incrementally (Unit basis) applied profile of a surface, with enhancements to make the definition of the increment explicit and clear, cover the "old" line applications and make profile of a line something a bit more unique to robustly control edges with a sphere defined tolerance zone, following the "True edge"... It seems worth considering to me.

I am mostly worried about "new" Profile of a line being limited to what's shown in OP and becoming unique "unilateral" solution different from "Profile of a line" elsewhere.

On not-so-closely related note - any suggestion on how to control size and shape of custom-designed spring?

Custom springs should be adjusted to the batch of available material to maintain the proper spring rate. So the form should vary. Performance, not form, is the main criteria. Form, such as OD, probably can use gd&t controls, but they need to take a back seat to spring rate in most cases, I would think.

Peter Truitt
Minnesota

to ptruitt:

Sorry, I probably misled you. By "custom" I meant "custom shape".

How to separate form from function in something like this:

If I was a rocket scientist making a rocket spring, I would use 'profile of a surface', excluding the coils. Since the number of coils would be fixed, I would allow the diameter of the coils to vary so as to have a means to accomodate the material batch properties to acheive the specified spring rate. But the spring supplier would understandably no-quote it and have some interesting comments such as: "Go away and don't come back". But maybe a custom checking and functional testing fixture would be the way to go and just put a photograph of the prototype on the drawing for reference subordinate to the controlled fixture designs and drawing notes.

Peter Truitt
Minnesota

CH,
You seem in touch with ISO, what do you mean "going the way of symmetry and concentricity". I was under the impression they are alive and well in the ISO world?
Frank

Frank,
Symmetry and concentricity are alive and well in ISO world simply because their interpretation is no different to the interpretation of ISO's position of nominally coplanar / coaxial features.

Actually in ISO GD&T world there is no tolerance that is interpreted similar to ASME's position. ISO does not play with terms 'axis' or 'centerplane' of actual mating envelope. Their position is more like location control of what is called in Y14.5 'derived median line' or 'derived median plane'. This leads to observation that, unlike ASME, ISO's positional tolerance also controls form of toleranced feature of size.

Which brings up a good point, pmarc. Since ISO sees them as identical to position, why bother having those two symbols?

Although maybe it's like flatness, which is identical to profile of a surface (if used on a flat surface with no datum references). I suppose there are several redundancies in ASME as well as ISO.

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

J-P,
I am probably not able to answer to your question in a way that would satisfy you. I guess only a member of ISO TC213 committee could help you.

Based on my experience I can just tell you that it is sometimes much easier to read ISO print's intent when symmetry or coaxiality is used instead of position. For example imagine a part having multiple planar FOS which are controled locationally relative to the same datum fature. Some of those FOS are nominally coplanar with the datum feature, some are not, but they are so close to its centerplane that it is actually really hard to recognize they were intentionally designed not to be coplanar. In such cases the distinction between symmetry and position helps a lot.

However there are also situations when position and symmetry callouts are both inconsitently used for controlling coplanarity of different FOS on a print. In one view there is position symbol shown, in the other - symmetry. And that is wrong - I am not saying illegal, but at least misleading. In such instances a lot of confusion can be created, especially if a reader is not familiar with ISO GD&T rules. Why create the confusion? Why not to be clear and precise?