Profile .002 to Datum A , 2 surfaces

[[Ky...]]

We have a part that is 9.800 long X 4.15 Wide Aluminum. The part gets taken down to .300 in the center and that is Datum A, which also has a big hole cut out of the center. The two surfaces that are calling a profile to are lugs that are 1.2 square and are .600" above Datum A. I am scanning the outer edge of Datum A .15 off edge all the way around. Then I am scanning the top of the 2 lugs. Datum A is not flat. But there is no flatness callout. I am having trouble explaining to the shop why their profiles are out. I can see it but I need to have a through explanation to be able to tell everyone.
There are no dimensional callouts on the print. Everything is by profile, or positional tolerance off the model.

1st Question : Datum A - does the CMM use the highest 3 points or the whole surface.
2nd question : How do I evaluate Datum A for profile LSQ, minimum ….
3rd Question: Do I evaluate each lug surface separately or as one surface back to Datum A.
Any other help would be helpful.

Welcome to Monday
Thanks
Kyle

Profile Callout.png

[[Ja...]]

The print calls out "2 Surfaces", so, recall both surfaces into one theoretical plane then hold that against A. Also, profile is a little overkill here, as all it would really control in this instance is parallelism to A (which is how I'd probably report it). If you must report it as profile, create an alternate alignment where you level to A, then recall all of A's surfaces points into one, singular point and use that point as X/Y origin with Z originating from A. You'll get the same result as if you had just called parallelism back to A, but it will show as profile on the report.

[[Ri...]]

Isn't that essentially co-planner?
Is surface one parallel and within the same location as surface two.

[[Ky...]]

I'm not sure. Could be. I need people much smarter then me to explain it to me so I can explain it to the shop. you know the CMM's with their voodoo magic way of checking parts.

Is there a way to plot out the profile in a graph to show the high and low points

Also is there a way that the high and low points in datum A are effecting the profile readings of the two other surfaces. I'm grasping at straws on explanations. I believe the CMM readings but need to be able to explain them

[[Ma...]]

I well try to understand an explain:

1. How do you evaluate th plane "A" as Gaussian... ?
2. Do you have one plane ore more planes with point recall?

I dont unsderstand complete your drawing or part Datum "A" is one flat plane? There is no "CZ"comon zone on the pic?! ❓ ❓

[[Cl...]]

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CAD - Evaluation - tick display & color gradient. This will show you +/- material from your applied tolerance.
I like to use spheres from the presentation drop-down. Its pretty easy to figure out. I use it a lot.

[[Ky...]]

Thanks Clarke,
I will try that
Kyle

[[Br...]]

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Do not do this. Profile controls location as well as orientation in this case. There should be a basic dimension to go along with this locating those 2 surfaces back to datum A. The 2 surfaces must fall within a tolerance zone of .002 that is equally disposed about the true profile located by basic dimensions. In other words, both of those surfaces must be within ±.001 of the basic dimension from datum A. Parallelism does NOT locate. It only controls the orientation to datum A.

[[Ri...]]

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It wouldn't control the location if there was a refinement of the location, correct? I thought I remembered seeing someone show an example of that before.

[[Br...]]

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If you use the Outer Tangential evaluation it calculates a plane that contacts the high points.

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use outertangential. This best represents the datum simulator as described in the Y14.5 standards.

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Evaluate them as a single surface. They must be co-planar relative to datum A

[[Br...]]

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If it were a composite tolerance then the lower segment would only constrain rotational degrees of freedom. Is that what you mean?

[[Ri...]]

viewtopic.php?f=13&t=1672&p=10658&hilit ... ent#p10658

I remembered this discussion.

[[Br...]]

In that case they put a plus/minus tolerance in there to control the distance between the feature and the datum. This isn't actully drawn correct. At least not per Y14.5. It should have been basic. You can't have plus/minus tolerances that aren't features of size. So we were trying to interpret what the intent there was. The way I understood Kyle's explanation was that there were no plus/minus tolerances. everything was controlled by GD&T.

[[Ri...]]

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Ah OK. I was just wanting to clarify a hypothetical.

[[Ky...]]

Thanks Brett and Richard,
OK so I use Outer Tangential for evaluation. I use Datum A for spatial rotation and Z origin. Will doing this affect those, or do I need to take 2 reading of the same plane.
In one of my classes we were told to do all of our filtering and stuff on the characteristic side and leave the features as raw data to pull from. So now 7 years down the road I am learning to do more and more, it seems that sometimes I need to do some things differently. So now I just need to learn when to do what at which times. Can someone loan me some more experience for a few years.

[[Ri...]]

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I'm not a big fan of the characteristic side only of filter/outlier settings. It tends to be a personal preference, but I will say that for constructed features you have to apply the filter/outlier from either the feature or from inside the constructed feature.

[[Br...]]

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I'm in this camp too. If you already have your filters and evals set they not only will transfer to the Characteristic side, they will be used in any construction or formulas that you might use to pull any data from the feature side.

[[Me...]]

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Favoring both yours and Richard's opinion on this matter raises some questions for me on filter/evaluation settings. Trainers are very specific about NOT doing it with features as opposed to characteristics, why is that exactly?

[[Ky...]]

OK So Both of you filter and outlier on the feature side? How do you set this up to do it this way automatically. If that is the best way I am all for it .
Like Shawn said the trainers were very specific about that. Thank you Shawn for chiming in I thought I had heard it wrong and was doing it opposite the way I was told in training.

[[Ri...]]

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There is no automatic way.

I believe that it is taught this way due to defaults, and also technically the official way to program is thru the characteristics side.

I'm not a fan of defaults. Just a personal preference though.

[[Ja...]]

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You're absolutely right. The two surfaces could be perfectly parallel to A, but still be too high or low. My apologies.

[[To...]]

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Being a former trainer, I disagree with that statement. For characteristics, having the evaluations set in the feature or the characteristic makes no difference on the report. However, if you do it in the characteristics, your Base Alignment features, where there could be a benefit, will not have them, unless you handle those separately.

It wasn't until I saw the cookbook where they stated it was preferred to be in the features "Because it creates a more stable feature" did I start to wonder. But like I said, in the end, the characteristics will come up with the same results. It doesn't matter where you apply them.

I learned, early on, about taking advantage of setting default filters and outliers under Save/Load Defaults. In fact, one trainer said it was better to use the default settings, though maybe not the most optimal, was better than not using any filters and outliers. So, by using the Save/Load Defaults, you could turn them on for all existing and future characteristics.

Calypso, now gives you the capability of making global changes in either of the settings editor, which once you get used to it, isn't too bad. Definitely, a good place to review your settings.

[[Me...]]

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Correction: My trainers, not ALL trainers. And specifically the "Preassignment evaluation methods like LSQ, Outer & Inner Tangential, not the scan Filter/Outlier & Elimination settings, my apologies!

I was also trained well before that damn book came out and ruined everything lol

[[Ky...]]

Thanks Tom , Richard and everyone else.
This is why I come to the board with questions to better understand the workings of the software and how to apply it to the crazy prints that the engineers draw.

Thanks to all
Kyle