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ACIS Solid is degenerated.
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* June 11, 2009, 12:50:37 PM
I'm trying to draw (3D) a groove in the face of a disk.  The groove needs to have different depths along it's length, which is broken up into segments. I draw the disc (2D) and the groove (in segments, which will be the different depths). I then extrude the disc.  For each segment, I create a hatch (which seems to be the only way to get a shape that will extrude), extrude to form a simple solid, and then do 3D add of the extruded segments to each other (or do a 3D subtract of the extruded segments from the 3D disk).  No matter which way I go, eventually I get error messages like "Operatin Unsuccessful" "The ACIS solid is degenerated".  An example is attached.  I'm pretty much a novice at 3D, so I may be overlooking the obvious.



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* June 13, 2009, 08:12:13 AM
#1
Hiya,

I have carried on your groove a little and have seen the problem you are getting. I have a workaround but it is a little tedious.


Firstly, the reason for the error.

Your lines that you added to segment the groove are not always placed at the end of the arcs. They are very close, however highlighting some of the arcs and zooming in to the ends you can see some have snapped to something nearby.

As a result the profile used for the extrusion is not always closed and you only extrude the lines. This will not form the solid you were after. Unfortunately in wireframe it looks ok. You will find out when you try the next segment (with the error). You can only see the problem when you use one of the render modes to view the part, I suggest hidden line removal.

The last subtraction you did on the drawing was an extrusion of lines only. It is this that creates the trouble. Have a look in the last part of the groove you subtracted, first in wireframe then hidden line.


There are two ways to continue.

1)  Redraw the segment lines, making very sure they snap to the ends of the arcs. This will make things much easier.  If this is not possible/desired then.
2) You will have to trim the arcs using line tools so the segment lines DO fall on an arc end. This will take a long time.


I used the Extrude tool.

To do this I had to select all the (repaired) lines of a segment then use “Join Polyline” to make it one shape. Then I extruded the Polyline and subtracted. Before moving on, I view the result in hidden line to make sure it was a good one. If not, a close inspection of all the line ends (after an undo) reveals the problem.

Note, because the segment line is now part of a bigger polyline you will either have to explode the last polyline or draw a new segment line to use on the next segment.

I am not sure what version of TC you are using. I have V16 Pro. Using the extrude approach uses the arcs nicely and does not make a large number of facets. However I am aware this may be due to using deluxe.


Sorry for the length of the reply, I hope it helps.  :)

Kind Regards,

Paul.

P.S. I have attached a copy of your drawing continuing the groove a little. (Saved in V16)



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« Last Edit: June 13, 2009, 08:15:25 AM by Paul »

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* June 13, 2009, 08:47:46 AM
#2
Many thanks.  I sort of figured it was something like the "not snapped to vertiices" thing.  I thought that I was being pretty careful when generating the primitives, but evidently not enough.  Thanks especially for the elucidation of how to use the "extrude" capability.  I was aware of it, but just didn't have a lot of time to invest figuring it out.  Once I get this design out of the way, I'll spend some time working through your tutorial.

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