How can I divide surfaces?

[Jim Estes]

I am working on a mold right now that is pretty much all curved surfaces. I need to part the mold in the middle of a curved surface. Does anyone know how I can divide the curved (compound convex) surface into two halves at the highest point in the surface? I can't use the ends because the surface changes radii as it goes along. Is there a way to use the interior lines to divide surfaces?

[erase42]

so i can visualize, you are wanting for example to devide that long narrow curved part in half length wise at the highest part of the radius wherever that falls?

[Jim Estes]

Yes, erase42, that is waht I need to do. I did a little work and came up with a way to get an approximate center, and I think it will have to do. I drew lines across the surface, extruded those lines thru the surface, then using boolean "union" and then unstitch surfaces I divided the surface into short segments. I then extracted edges from those short segments, then I placed points on the radius line segments where I thought the highest point was, then I used arc-3 entities to get a radius that was very clost to the highest point. Then I extruded that radius inthe z axis in both direction to get a surface that I could use as a knife to split the original surface into two segments.

The only problem I have is that when I did the final split, one surface disappeared on me. I have no idea why, but it just didn't show up after I did my final boolena operation with the "knife" surface and the orignal surface, when I unstitched the surfaces, one surface disappeared. I also had one of the short segments of the surface to disappear when I did my first boolean-union-unstitch operation.

I attached a file if you would like to see what I did.

This was a lot of work for something that seems like it should be so easy.



I have the different parts in different layers.

[erase42]

wow, i didnt get into it too far before i fell solidly asleep at the computer.
it does seem like a hell of a lot of work to do that seemingly simple of a thing.
Toby would be the man on here that i would expect to know a trick if there was one. but i fear that in real life thats the sort of thing you need to be planning on when you actually start drawing the part.

[Jim Estes]

That's part of the problem, I didn't draw the part, one of my customers customers did. And from what I can tell they did it in pro-e. I did some thinking on the subject and I got to wondering if I could just reverse engineer the lines used to draw the original surface and then break the surface into two parts, then re-create the surfaces. I am doing some more work on this so there will probably be some updates to this thread.

[tobyaxis]

You guys don't like easy parts do you? Ok, I did some thinking and your on the right track with what you discribe in post #5. You will have to Make a copy of the original file and in the Copy use the Booleans function to Union the Surfaces. Then you will use the Extract Geometry from Solids and Surfaces.

A bit of warning, your going to have a lot of Spline Geometry. It will be best if you separate the different segments using Colors and Layers.

I'm still waiting to see if V22 will have these functions available. For right now we have to do it the long way.

That looks like something from Pro/Engineer.

[Jim Estes]

I know what you mean about the splines. Is there a way to turn splines into are segments? Not having radii is a big part of the problem, I can't find the high point of a bunch of line segments very easily.

[tobyaxis]

Originally Posted by Jim Estes I know what you mean about the splines. Is there a way to turn splines into are segments? Not having radii is a big part of the problem, I can't find the high point of a bunch of line segments very easily.

That can be done. Select you Surface>Extract Geometry>Unselect All>Now Select you Extracted Geometry> Other Menu>Splines> .0001 >OK. Walla!!! Arcs

[erase42]

toby when you say "extract geometry" is that the same as extract edges?
i think you have buttons i dont

[The One]

Jim,

Is this what you are after? If it is I will tell you how I did it, but it is several steps that are better explained on a need to know basis. Due to the length and detail. BTW, I was able to complete this in 20 minutes.

Regards

[Jim Estes]

OK, THE ONE, I see what you did there, nice works. That is what I was going for, I just couldn't see how to make the "knife" surface that you used to split the surfaces. That's a good way to create a nice even surface-- laying the radius down into the x-y plane. Then use the -move to Z function.

That's one area where I am lacking experience, changing these complex parts into 2D so that I can work with them and them changing them back to 3D.

Thanks,

[The One]

It was actually relatively simple but detailed.

1) Extract the Edges of the surface.
2) hide the surface.
3) Use the Point on Entity function and place Points on one side of the extracted shape, in varying intervals, leave the ends alone. You definitely need more than one or two for this shape and I avoided areas where the topology of the edge changed drastically.
4) Select the opposite side of the contour and the points that were created in the last step
5) Use the Point Perpendicular command so that you have points on both sides of the contour.
6) Join the Points together using the Line Join command. (NOTE: select two perpindicular points and select the menu option. select the next two and press F4'repeat last')
7) Use selection criterium to select and delete the Points only. (Edit -> Select)
8) Use Point on Entity to create new points in the middle of the lines created in step 6.
9) Rotate the Points around X.
10) Move to Z the points (all to Z0, not relative).
11) Select the points in order.
12) Spline the Points with the Interpolated option (.0001 accuracy).
13) Use Extrude Curve to create a Surface out of the Spline.
14) Rotate the new Surface back so that it is in the proper orientation.
15) Unblank the original surface.
16) Position the surface extrusion so that it falls in line with the part in X and Y (Z should be fine unless you didn't use enough points).
17) Boolean -> Union the surfaces together(this creates an edge in the middle of the original surface).
18) Unstitch the surfaces and delete what you don't want.

Hope this helps.

Regards