Profile Application

[Travelled]

New to this so bare with me, 1st Post.

I have a print that calls out profile to itself. At 1st glance one would assume this to be true. The entire print shows Profile Tolerances with no Datum identifiers. The Notes identify (UOS, all dimensions are in relation to the hard point nest). The print shows limit dimensions relevant to datums as well as profile tolerances. In all cases of the profile callout, they refer to basic shapes, angles, radii, etc... The nominal shape. I cannot locate dimensions to many of these surfaces, the only control are basic dimensions and profile to itself callout. My worry is the machining of the part which leads me to my interpretation, all profiles must be controlled back to datums as that's how the print is being dimensioned. Correctly or incorrectly, I know how to measure parts and what's important to my customer. My problem is hardheaded engineering staff who contacted the customer and lead them into the answer they wanted. Now, both sides would look like idiots if they decided to do what I consider the sensible solution. As it stands, I'm in a battle with people that seem to not understand and just want a conforming answer. The question then becomes more of a statement.

 

[3DDave]

Welcome to my world. Where people would say, what if I just lit the end of the fuse, not the whole thing? That's OK, right?

Other than that, a simplified version would help others to understand your particular predicament.

 

[CheckerHater]

Dear Travelled,

It would help greatly if your post had less rant and more detail to it, for example:

What set of standard are you using, ASME, ISO, or your own company's "creative drafting"?

Also, what exactly do you mean by "profile to itself"? Profile may be used many different ways, not all of them are obvious or easily understood/accepted.

So please, give us better idea of what's bothering you.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[greenimi]

I agree with CH!

 

[Travelled]

I got this up yesterday in a hurry and apologize. I see where I'm ranting which at this point is not surprising at all. I tried to attach a document but can't seem to figure it out though my company may be blocking it. I may have been able to upload an Excel sheet which gives the needed detail. I can possibly upload the whole print.
My print establishes datum's with a general note, UOS, all dimensions in relation to the following, etc...
We work to Spec.(GEAE, P1TF108) which calls out ASME Y14.5.

Their are limit dimensions shown on the print but not for all features, the remainder are controlled by profile callouts.
The print shows basic dimensions establishing the true contour with a profile modifier, no datum's noted.
I've tried to minimize the explanation hoping not to cause extra confusion. Hoping the attachment works. Hoping I've done enough to get my point across enough for understanding.

 

[greenimi]

Profile circled will control the form error only. Not the orientation or location.
So, what are the specific questions?
Please kindly advise.

 

[randomdrafter]

@Travelled , posting entire print may not be good idea.

 

[Travelled]

Thanks for advice on posting print.

The question was answered. The Form is controlled only as shown. At issue is the location of the features shown. These are not controlled on the print properly.

From a strictly practical purpose, I'm having a difficult time at my facility. Everyone here believes this to be as stated above, a form control. I can agree but from a practical standpoint, there is nothing controlling position and machining of the part could be affected. I'm standing firm that this callout has to control position as well as form though I'm not making any friends.

My simple viewpoint is that all features of a part need to be controlled directly or indirectly back to position. Even airfoil shape or core contour has control back to position in some manner.

Thanks for the responses as it becomes clearer and clearer to me that many do not have a real good understanding of GDT. I put myself in the same category but I continually ask myself what would I want as the customer.

 

[greenimi]

RE:"ask myself what would I want as the customer "

So, are you guessing what your customer wants instead of asking ?

 

[Travelled]

We did ask and they came back with a Profile to itself answer which doesn't control the machining of the feature. It was a loaded question of course.

 

[randomdrafter]

You just ask them whether they want to control the profile from specific datum's.I guess X,Y & Z are datum derived from casting surface...

 

[greenimi]

I would say the location and orientation of the shown shape is controlled from the datum features shown/specified in the text.
The form is control by the profile callout.
All of the dimensions should be basic.

IMHO you already have a full definition of the product.

By the way, to control form from the specific datum's, it is kind of incorrect verbiage because the form itself is not related to any datums (see circularity, cylindricity, flatness, DML and DMP are not related--BY DEFINITION-- to any datums).

 

[Travelled]

I agree with your take on this but the note doesn't tell me the extent of my tolerance. I have to apply the profile to the basic dimensions. The basic dimensions establish the true contour or my basic shape. I then apply my profile equally to the basic shape. This is how I'm proceeding for lack of a better answer.

And IMHO, I agree as well. There's nothing wrong with the print.

ASME Y14.5 states that Profile does not require Datum Identifiers. I see what they're trying to do on this print. What they should've done was to include datum qualifiers on all of these profiles as it would've answered a lot of concerns.

 

[axym]

Travelled,

I would have several major concerns with this print. I agree that the location of the surfaces relative to the datums is not controlled, but I would say that the overall form of the part is not controlled either. The profile tolerances are applied in a way that does not make sense when the rules and conventions of ASME Y14.5 are applied. Whoever created this drawing appears to have ideas about profile that are very different from what the standard defines.

The two profile callouts that are circled (annotation bubbles 137 and 140) each control one surface only. In other words, they each define a tolerance zone for the nominally flat surface that the leader line is pointing to. No datum features are referenced in these callouts, so the effect is equivalent to two flatness callouts. There is no control over any of the other surfaces (the angled surfaces, the fillets) in that view - the basic dimensions don't impose any kind of tolerance requirement.

The same thing is true for the profile callouts in the lower left view on the spreadsheet (bubbles 54, 59, 73, 74). These each control only the flat surface that the leader line is pointing to.

There is further confusion in the lower right view. There are two profile callouts (bubbles 77 and 97) with different tolerances, each with the annotation ENTIRE SURFACE. One is pointing to a surface on the part, and one is pointing to a leader line. This is a non-standard annotation, and I'm not sure what the intent was. It's not clear what the "entire surface" refers to - it can't be the entire surface of the part or all the surfaces in the view, because the .004 and .024 tolerances would conflict.

The general note establishing datums is non-standard and unenforceable as well. Dimensions are not defined in relation to datums - it's supposed to be feature control frames (callouts) that reference datums.

There appears to be significant misunderstanding about the distinction between dimensions and tolerances, how basic dimensions work, and how geometric tolerances are specified.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[Travelled]

Evan, thank you for your comments. Believe me when I say they're appreciated. I think I stated previously, I'm nowhere near an expert at GDT, nor ASME Y14.5. I do however feel I've got a firm grasp on a practical approach to dimensioning and control. As well, if it doesn't seem right, it probably isn't and as you stated, this print has some issues.

When I read ASME Y14.5-2009, the general statement of "Profile tolerances are used to define a tolerance zone to control form or combinations of size, form, orientation, and location of a feature(s) relative to a true profile. Depending on the design reqt's., profile tolerance zones may or may not be related to datums. A digital data file or an appropriate view on a drawing shall define the true profile.

My take on this is that my form is defined by basic dimensions on the print creating my True Contour. My profile tolerance is then equally dispersed about the true contour and it establishes my tolerance zone. I don't move it or my shape to be inspected, I just inspect my shape to the zone established as it's held to datums. For lack of a better answer, this is what I'm going with.

 

[axym]

Travelled,

It sounds like you're inspecting the part in a practical way, that represents the functional requirements. The problem is with the drawing - it doesn't control the part in the way that represents the functional requirements, so you're inspecting it in a way that drawing does not technically require.

If you have Y14.5-2009, you may want to review the sections on profile zone extents. Specifically, Fig. 8-5 on specifying profile of a surface All Around. If the profile tolerance is intended to apply to all of the surfaces in the view and not just the one that is pointed to, then the all-around symbol (circle on leader line) needs to be present.

The other thing is holding the part to datums when inspecting the profile. Technically, the drawing does not specify this properly either. The attempt is made in the general note, but it is not written correctly. The profile callouts should explicitly reference datums X, Y, and Z.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[Travelled]

I agree. My issue on this print is that all of the other basic dimensions in that view are not controlled anywhere else on the print. I've got no choice except to inspect it to what is shown and explain it just that way.

I could rant on and on but I'm comfortable with my approach.

Thanks again.

 

[greenimi]

Looks like Evan is correct.... again. I think the designer tried to use half of the note on the end of 4.4 /1994. He ( maybe ) was thinking that the other half is redundant anyway. ( something like why do I have to put datums in the FCF since I already have stated which is primary, secondary etc. Just to cluter the drawing which is very busy anyway due to the part complexity)

I also agree with Evan that is not very clear if the profile shown is applicable to the entire surface ( and some smaller size profiles are refinament of the bigger one or maybe a general profile is already specified on some other attached /referenced documents shown on the drawing) or the shown profile is applicable to only the surface shown with a leader line ( as the standard states)

For example dimension 74 ( lower left drawing) include the radius or not? I assume yes, flat surface being very small ( I know, ......very weak argument)

UOS, I will ask the customer and if no answer or the answer is something like " what are the functional needs are already specified on the print" then I will read that the entire part surface is in .024 (biggest tolerance specified on the print with the note "entire surface") with the exceptions of the other shown profile surfaces with smaller size tolerance.