Angular True Position? 2

[trickysheep]

I am a little stumped here. I have a part which we laser etch 3 small rectangles onto. The laser etching is called off of the centerline of the part, at 12 1/2 degrees 3 places. It has the true position box around it. The only tolerancing on the pads is a width of .120 +/- .020, and a box which gives .030 max material. How can I transfer this to an angle and find where I am?

 

[weavedreamer]

If the angle is Basic, there should be a geometric tolerance governing the attributes of your target pads.

 

[drawoh]

trickysheep,

When you say "True position box", you mean that there is a box around the dimension designating as Basic, right?

It sounds like your drawing is missing tolerance boxes. You can apply a true position tolerance to your boxes. Another option is profile tolerances.

Without any of this, I would regard your drawing as uninterpretable.

JHG

 

[dingy2]

There seems to be lots missing here. Does the angle have a rectangular box around it? If it does, it is basic (theoretical).

Positional could be of the 3 holes but it must be relative to each other or to some other datums? mmmm?

Dave D.

http://www.qmsi.ca

 

[KENAT]

Agree with others, there seems to be a lot missing here.


KENAT, probably the least qualified checker you'll ever meet...

 

[ctopher]

What is the laser etch for? Is it part of helping in making the part or alignment within an assembly? If it's for some type p/n marking, etc, the GD&T is probably not needed.

Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog

 

[trickysheep]

The 12.5 degrees is basic. The only thing I have to go on for a tolerance block is the pad callout of A|B M | Ø.030 M
with the "M's" being the max material symbol. A is the backside of the flange, B is the O.D. of the flange. The pads run from the I.D. of the part out and are spaced 120º apart. Having .030 + the max material, I don't see how I can figure out any radial tolerances out of this....am I wrong?

 

[KENAT]

Does the feature control frame not even give the fact it's positional?

Are the 120° not basic?

The length of the pads are given by the geometry of the part right, running from ID to OD?

KENAT, probably the least qualified checker you'll ever meet...

 

[PSE]

trickysheep,

Can you gain read access to the underlying CAD model (assuming there is one)? If you can view it or access it you might be able to find your missing information. I have encountered drawings that had lots of information on feature tolerances etc, but nothing to tell me the basic size of the part. Instead we were to refer to the CAD model as the master for the geometry. I would have been OK with that except that we had no read access to the models in order to bring them up.

Regards,

 

[trickysheep]

There is no cad model. The pad length is given as a minimum, with the start point dimensioned at .825 +/- .040 from center of part. The 12.5º and the 120º are both basic.
The pads run from I.D. to O.D..

 

[weavedreamer]

The positional tolerance on the pad width should strike your zone on the 120° Basic C/L's which are set up 12.5° off of another feature? The positional should not have the Ø tolerance zone then, and from the sounds of it, a tertiary datum as well.

 

[ringman]

If Im reading your comments correctly, it looks like they are mixing bilateral and basic dimensions for the location of the pads. THIS DOES NOT CONFORM TO Y14.5, if that is your referenced document.

 

[KENAT]

tricky, can you post the relevant section of the drawing?

KENAT, probably the least qualified checker you'll ever meet...

 

[trickysheep]

This is the first time I have ever tried to post....hope it works!

 

[KENAT]

Took a while to open but... Looking at it it kind of makes sense except:

I don't think they should have used the diameter in front of the .030 in the position FCF.

I'm also a little thrown by the order the FCF are in.

I think though that essentially the position is only applied to the angular location of the pad. The width of the pads must be 'centered' at 12.5° from the 'notches' plus or minus .015".

Others will be able to clarify/point out my mistake.

KENAT, probably the least qualified checker you'll ever meet...

 

[ewh]

I agree with KENAT's explanation.

That drawing is definitely not per the current Y14.5 standard.

 

[vigildesign]

Kenat is correct for the size of the etching (if it considered a feature like a cut)at its' smallest width at .100(MMC). But at .140 (LMC) it can be off 12.5° ±.035.

So from the information that is on this unusual print, the size of this etching is .260 min long X .100 min wide and its 3 locations are 120 degrees apart with basic dimensions giving the spacing between them .030 to .070 tolerance (dependant on size of features). The tolerance from the center axis for the innermost etching side is the .825±.040 dimension.

I am pretty sure you can hit this tolerance with the etching.

This drawing is so wrong. The only thing you can give them is what you are able to determine from this print unless you ask them to give you the numbers you need for your job. You don not need the positional tolerance.

Marcelino Vigil
GDTP T-0377

 

[trickysheep]

We received a rejection stating the 12.5º was actually 10.25 degrees, they stated in the rejection the tolerance was +/- 2º. That is the UOA angular tolerance from the standard tolerance block! I don't think they know what they have drawn either! The part that makes this quite difficult is it is a customer supplied STAMPED PART!!!!! The 3 "notches" that I need to align from are stamped. Not an easy alignment I can assure you.

 

[KENAT]

vigil, you're right I simplified out the MMC that's what the use of '' on 'centered' was meant to indicate. However, if it had been done correctly I think the positional tolerance is needed/would make sense. Dimensioning it like this is not quite the same as having a tolerance on the angle.

tricky, when looking at a drawing this confusing almost anything goes however, assuming I more or less correctly understood the intent of the drawing, their QA are full of ****. The 12.5 is basic so the block tol does not apply.

You have my sympathy, although whoever accepted the print to bid against should have asked for clarification at that time (I know in the real world this is often time consuming/not considered worth the effort though).

KENAT, probably the least qualified checker you'll ever meet...

 

[Standing]

In my humble opinion this should have been dimensioned using profile tolerance. The diameter symbol before the .030 is not correct because the .120 +/-.020 is not a diameter.
I would write an ECN to change the tolerance to profile. In the mean time I would argue that the diameter symbol before the .030 is a mistake. Saying it should have not been put in there and convince the powers to be too use the .030 as if it where a profile at MMC.


Bradley
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