Symmetry plane construction by two cones

[[FR...]]

Hello,

Anyone has suggestion on how to construct a symmetry plane in between two measured coaxial cones? As shown below, I need a symmetry plane which the direction will be +X or -X.
BTW, can Calypso construct a plane through a measured or intersection point, and the direction of the plane can be customized?

[[Cl...]]

I'm not sure that I would trust that construction?

[[FR...]]

Yes It is easy to construct a symmetry plane if those two cones are planes, Calypso can easy do that. But those two cone surface are my datum reference and I need to use them to construct a symmetry plane to define as my spatial plane. I also need to use this symmetry to offset later to get its intersection points with cones later.

[[Cl...]]

Please sign in to view this quote.

I don't understand what you mean by; "if those two cones are planes"

[[Jo...]]

Is that not really ONE cone sectioned off ? Also what hierarchy is it for Datum ? As primary I wouldn't trust that to have a good vector in one direction. If you have a reliable surface, maybe the symmetry of the two planes shown, you can construct a theoretical plane in secondary alignment using formula for X direction extracting only the center of cone..

[[FR...]]

Clarke,

We used to have those two faces as planes, for that case I can construct a symmetry plane as my spatial control. But this time those two surface are not plane now, they are part of coaxial cone surface and cones in X direction.
John,

As I mentioned above, those two partial cone surface are my primary datum which control part's five directions of freedom, and the last direction controlled by the stop face.

[[Cl...]]

I would use "Symmetry", not "Symmetry Plane". Symmetry recalls two features, symmetry
plane recalls two features points. The latter is used if you need bonus tolerance, and will
not give as stable a result as plain symmetry.

[[FR...]]

Yes I did use construction - symmetry, not using feature - special geometries- symmetry plane. Just for explanation of my features.

Now I need to find a way to setup my alignment.

[[No...]]

I may be suffering from vision disorders, but I still can't see how these areas are cones 🧑‍💻

Just to make sure: Are you absolutely sure they are cones? Because you can't trust what Calypso thinks they are. Calypso always uses geometry approximation, so it even declares freeform surfaces to be spheres, cones etc.

[[Ri...]]

You have what appears to me to be two planes, opposing at an angle.

Or is it indeed two separate cone segments, side by side, with their arc radii being so large that they only appear flat in those two small sections?

Like this pic below?

Except with a "much" larger arc radius? (imagine this cone on the right is sweep cutting the plane on the left) and your wanting the midpoint/symmetry plane between the left and right cone?


I made my cone arc small just for easy illustration. A cone arc so large as to appear as a plane would mean you have a very, very small sample section. The smaller the arc segment, the higher the uncertainty.

I'm genuinely intrigued 👩‍🏫 Can we get a better look at the feature in question?

[[FR...]]

Richard and Norbert,

Those two faces are definitely not planes. I confirmed with designer and even with PCDMIS. Here are the view and zoomed view.

What I got so far is, 1st try to get a symmetry from 2 cones, but Calypso say no as it grey out results.
then I use intersection by 2 shell boxes checked, got a intersection circle I think but not sure.
Now if this intersection is a circle or point whatever, how can I use it to construct a plane through it, and the plane direction can be defined to any direction I want?

[[Me...]]

Let me try an explain this better. Technically there is symmetry between the cones but based on the size of the surfaces you're going to have a really hard time getting a reliable result. Both for location and size. You'd be better off doing some sort of Best Fit of a bunch of points as opposed to trying to find the true location of those cones.

[[Ke...]]

Please sign in to view this quote.

Adding on.. I was thinking that a Base Alignment using stable features, the a RPS Freeform (Looped) secondary alignment- using as much of the cones as possible. (track the Delta to study reliability of the method)

[[FR...]]

I agree these two faces are small and very hard to get reliable results.
These two faces are the assemble locking faces which customer using them to slide and lock the blade into position (it is something like V-block but the V are cone surface), each blade side by side and this is how a turbine engine be assembled. As Keith said, I used other reliable large flat surfaces to have my start and BA, then I measured these two cones.

The question I am facing now is, can I get a symmetry constructed plane in between and with the same direction of these cones? If i can't, then in Calypso, can I constructed plane through a known point, and this constructed plane's direction and be defined on any direction?

[[FR...]]

Also the reason I need the symmetry plane is, it is the blade root center plane and it is the primary datum.

[[FR...]]

Okay now is what I got. Got a intersection 1 ( circle) as I mentioned pic above, then define a plane by theoretical feature, formula XYZ and direction, then a plane, but it is colored pink! which I think it is not a successful plane.
Any suggestion?

[[Er...]]

Thats most likely a fan blade, for the compressor. Not a blade located in the actual turbine. (the hot side) Unless it's a aerospace part, but it looks to heavy for that. For those who cares...

I have done hundreds of programs for blades while working for my employer, one of the two largest turbine manufactures in the world. So with the knowlage Ive gathered during these years, my opinion, forget about symmery if the surfaces a conical.


Usually the pressure flanks have a quite tight form and/or orientation tolerance. And since thay are conical, they control all aspects of the airfoil location and orientation. So if it was my task, I'd make the assumption that they are pretty good.
Try five points, distribued as a five on a dice. On both pressure flanks. Best-fit these 10 points. In that coordinate system, create a Theoretical plane at nominal location.

If you are looking for really high precision, I would also rotate (lean towards pressure and suction side) around Y axis judging on the picture by half the angle of the cone, one side at the time. So you can repeat the best fit, this time with more points, and only allow translation in X and Y, avoid rotation is this step. Not super easy to explain, but I'll think is clear enough. Based on the translation values from the last two best fit, you can create a new theoretical datum plane. Repeat if nessisary.

If k-point is defined at a basic height of the pressure flanks, that can be created in a similar Fashion. (based of the translation values of the best fit and asuming form is good. And then all degrees of freedom is locked.

But this is a suggestion, that you can build upon, with curve etc. But make sure you analyze the result. No one wish to die in a plane crash :p


Btw, May I ask who you make blades for?

[[FR...]]

Thank you Eric! 😜

I feel it will work after read your reply, and it would be the best solution so far to get a theoretical datum plane( symmetry plane or whatever call).the only uncertain thing is, I need to define this theoretical plane successfully later.

I joined aerospace industry one year ago, and this part may not for engine, maybe it is for compressor which I do not have too much clue between them. This part is for one of our customer, Elliott.

There I also have question about this Calypso software, on how to construct free form surface by using 3D curve. If you could read my question " free form construction - why perfect 3D curve turned to bad form ", and give me some suggestion please? I am struggling and your suggestion will be great help!

[[FR...]]

ooh that is perfect! I got my offset plane and intersection points to define the Z plane! thank you Eric! 🤣