Same plane different results

[[To...]]

Hello

I am programming a new part for a customer, and I simulate the part in Calypso on my offline seat as I always do.
But this customer uses form tolerance a lot more than I am used to and I get some results that I really do not understand.

I am evaluating a plane and I do 6 points on the plane. This feature I put in my form and check according to base alignment.
Result is 0.3". Tolerance is 0.02".
Then I extract the same plane and use a scan around the plane, and evaluate form in the exact same way as before.
Results is 0.0008".
It is all simulated.
How come the difference? I do see that there is a difference in x coordinates and A1 & A2, but what I don't understand is why it isn't the same, when planes is the same feature that I have extracted.

[[Ju...]]

Could one of your points be to close to the edge of your part ? Maybe just a bad placement.

[[Ri...]]

I've had similar issues before, look at the points you selected on the model, one or more may be embedded below the surface.

[[Ro...]]

I have a family of parts i'm programming, and i take 2 very small planes on very small surfaces for 1 profile, it ALWAYS checks out of tol in simulation. when i send it to the machine it checks real parts fine, but it does not play well in sim.

could be a bug or glitch.

with the plane feature open, Right click on the model and select "View Actual Points" and set your scale to 5 or 10, see if you can spot the deviation.

[[No...]]

If it's all simulated, why even bother about differing results? I mean, the results calculated by the dispersion are purely artificial and pseudo-random and have absolutely nothing to do with the geometry of the part, meaning that Calypso doesn't "measure" any points on the CAD model. It just generates a set of random points based on the strategy and dispersion settings.
With this in mind, the only interesting question would be why the math behind the dispersion algorithm behaves differently when operating on fewer points.

[[Me...]]

right click show actual points to see if anything else is going on. Or try to eval the profile differently to find out if its inward or outward, because the profile is just an absolute answer and not helpful to find where the surface actually is.

do more scans towards the inside of the plane, the plane could be bowed or bulged. plotting a color map can help visualize this.

[[Ow...]]

Open up the strategy on the plane with the 6 points and select the notepad icon with the points list (upper left corner) and see if all the X nominal points are of equal value.
I'm betting they're not and there's a bogus point in there that just didn't select right on the model face.

[[Ro...]]

This is may part in Sim, this is the only dim out of maybe 15 profiles that does this, but it does it on every part.
Now with a real part its fine, only the Sim flips the vectors and has the huge form err.

jhkghfghfdsda.JPG

[[Ri...]]

Please sign in to view this quote.

As an FYI
I never use dispersion, I write geometry as pure as I can. When I run thru simulation and if my results are not 100% perfect, I more than likely made an error.

[[Ro...]]

Please sign in to view this quote.

I DO USE dispersion, because i do so much with PCM that i can usually tell by results if ive made an error.
For instance, profile Min & Max are big in the shop i work in, its been ingrained to the setup operators to watch those numbers more than the actual profile deviation (it has to do with PCDmis and the strange way that PCD calculates profile) so in order to make the report as clean and readable as possible i put the Min & Max values into the comment. but if i screw something up then the dispersion numbers i get will almost always point out the flaw in my results.
Eg: If my profile measures .0012 then my largest Min or Max had better be .0006.

[[To...]]

So I did find out what is wrong.

Instead of using points I should use space points. Now my simulation is perfect.

Thank you for all the inputs.