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Sketch flips when plane is moved

A

andrew86

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First, let me explain what I am trying to do. I have a model of a nosecone-shaped object with a textured surface. It was imported by an IGES file, so I don't have any equations for the surface features. I need to map the surface of the shape with coordinates so I can compare them to another untextured version of the same shape.


I created a datum plane that goes through the central axis and is at a certain angle with respect to the top plane. This angle is controlled by a parameter. On this datum plane, I made a sketch and made the cross section outline an actual line. I then placed a small circle on the surface that I need analyzed. This circle will be used to mark the current analysis point in a sensitivity analysis, but that is getting ahead of what my issue is here.


The sketch is fine as I increase the angle of the plane and the curve made from the cross section updates automatically. At 25 degrees, however, the sketch flips to the bottom half of the cross section and the circle is now on the inside of the solid instead of on the surface. I can't figure out why the sketch flips at all, since nothing really changes at that angle. Does anyone have any advice on this issue?


Thanks in advance! This has been bugging me for a while now.
 
You didn't say, but I'm assuming the circle is tangent to the cross section? If so, there are two tangent solutions, inside and outside. You drew it outside, but there's really nothing to tell Pro/E that it should be outside. My guess is Pro/E is assuming it's position relative to a default plane, maybe the top plane, and as the angle increases it flips to keep it a similar distance from that plane.

You can likely get clever with your constraints or construction geometry to force the circle to stay outside the sketch. It's hard to make recommendations without seeing the actual part. You might try changing the reference plane for the sketch to be a created datum through the axis and normal to the sketch plane. Then, as the sketch plane rotates, the sketch orientation does as well. I suspect that will fix it.

Edited by: dgs
 
The circle is part of the sketch that is on the plane of the cross section and it references the curved outline of the cross section. I am playing around with different constraint configurations now ... it must be something simple because I don't see what would cause the sketch to flip like this.
 
Here are images of the model --- the first one is when the rotating plane is 25 degrees from the xy plane and the sketch is the right orientation. The second image is when the plane is 30 degrees from the xy plane and the sketch is flipped






Edited by: andrew86
 
What is the spot referencing for it to move from a point on the outer curve to one on the inner, looks like the x dim is the same?
 
The circle is simply a marker in the sketch that I set a dimension to. I then use a sensitivity analysis to move the circle from one end to the other to map the outer surface. That's why the circle has to be on the outside of the solid and that's why it's in the same x-position for both sketches.
 
Try making a datum plane through the axis and normal to the rotating plane. Then redefine your sketch plane and select this new datum as the reference plane for your sketch. Not sure it will help, but I'm thinking that it may help 'orient' proe so that it can more reliably assume where that point is.

The interesting thing is that it's changing loops, not simply flipping inside or outside the lop as I had understood before.
 
Unfortunately, I am not allowed to post this file. I tried making a second plane that references the rotating plane and it still flips the sketch. I appreciate the help, though, this is a frustrating little problem.
 
Just to make sure, did you set that new plane as the reference plane (TOP, BOTTOM, RIGHT or LEFT) for your sketch?
 
Something that may be of use is to extrude a surface on the rotated datum that uses a sketch setupwith theYZ plane as the sketch reference and the ROTATED datum oriented RIGHT. For the sketch references use the ROTATED and the A_1 as sketch references. Select the outer cone surfaces and intersect them with the extruded surface.Since you are trying to get measurements of the surface you could create a field point on the intersection curve, create a saved analysis, create an analysis feature, group the field point and analysis feature, and run a UDA. I can post a sample that is similar to what you have shown if you want to see if it will work for you.
 
That sounds interesting ... would you mind posting an
example? I really appreciate the help, I've been working on
this for too long.
 
My model was imported using an IGES file, so the surface consists of many individual quilts. Is there any way to join all of these quilts into a single surface so I can use this method? This method would work perfectly if I could get this surface joined.
 
What might work is to create a copy of the outer surface using the seed surface selection method. Select a surface element on the outer surface, hold the SHIFT key, select the end surfaces of the cone (you can release the SHIFT if you need to rotate the model to select the other end surface, just hold the SHIFT key before making the selection), and copy and paste. This should create a single quilt surface.
 
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