Trouble opening pipe

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 From:  Involute
8492.1 
So I'd like to make a pipe along the curve between the two concentric circles on the inclined plane and the two beneath the model (of course, the circles represent the outer and inner diameter of the pipe). I can make the pipe with the Sweep command, and open the end where it passes through the bottom of the model after unioning the pipe with the model. The end on the inclined plane, however, remains closed and I can't figure out how to open it. I.e, there's supposed to be a hole in the outer surface of the inclined plane leading to the pipe, put the pipe end just remains merged with the surface.

I can imagine pulling the curve and circles out beyond the surface and then deleting the extension, giving me access to the interior of the plane, but it seems to me that shouldn't be necessary. What am I doing wrong?






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 From:  BurrMan
8492.2 In reply to 8492.1 
putting the pieces together isn't hard, but you have to start with "Your pipe cant make that bend"....

Secondly, your sweep doesn't "go all the way" to that surface.

EDITED: 25 Jun by BURRMAN

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 From:  Involute
8492.3 In reply to 8492.2 
I can adjust the bend, but how can you tell the end of the curve isn't on the surface? It seems to be snapping to it in Left/Right view.
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 From:  Michael Gibson
8492.4 In reply to 8492.1 
Hi Involute, just to illustrate what Burr says above, your pipe is going to be malformed because the path has a bend in it that is tighter than the pipe diameter. This means the pipe will bunch up on itself here:



It's possible that bunching will also mess up booleans too since self intersecting surfaces can mess up intersection calculations.

- Michael
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 From:  Michael Gibson
8492.5 In reply to 8492.1 
Looks like your circles are just a little bit off the plane, about 0.003 units underneath it. The end of your path curve hits the circles right on but the 2 circles are just barely below the plane:







- Michael

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 From:  Involute
8492.6 In reply to 8492.4 
Aah, I didn't notice that kink. I can work that out, but how can I tell if the end point of the curve is on the surface or not?

Edit: Never mind. Our posts passed in the ether. I see now. Thanks.
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 From:  Involute
8492.7 In reply to 8492.6 
Still, is there a test, other than zooming in, to tell whether a point is on a surface, instead of just really, really close? If not, how do I know I'm zoomed in enough during inspection?

E.g., as far as I can tell, the end of the curve in this attachment is on the surface, but I still can't open the end of the tube on that surface (I've left it un-unioned to make it easier to inspect).

EDITED: 25 Jun by INVOLUTE


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 From:  Michael Gibson
8492.8 In reply to 8492.7 
Hi Involute,

> Still, is there a test, other than zooming in, to tell whether a point is on a surface, instead of just really, really close?

Not really - well I guess if things seem to be behaving oddly that's a sign to do a closer inspection.



> If not, how do I know I'm zoomed in enough during inspection?

I go in something like 6 or 7 pushes of the mouse wheel. You don't want to go in too extreme because when things are only say 0.0000001 units apart that's totally ok. It's when things are more than 0.001 units apart that they're going to be considered separate pieces and won't intersect with each other.


> E.g., as far as I can tell, the end of the curve in this attachment is on the surface, but I still can't open the end of
> the tube on that surface (I've left it un-unioned to make it easier to inspect).

That's actually normal - union doesn't really open holes in things, it combines things together and only removes pieces that are contained inside both objects. So the part that you want to have as a hole isn't contained inside the hollow tube you have, it's only in the main body volume so that part will be kept.

For drilling a hole you want boolean difference for that instead of boolean union. If you want the inner tube to be totally open all the way through you want to have 2 separate tube objects an outer and an inner one - first do a boolean union with the outer tube and your main object, then follow that by a boolean difference using the inner tube as the cutting object.

Here's a simplified example - if you have this tube solid and this sphere solid:



When you union them, it gives a result like this:



They are combined into one object now but there's no hole through the sphere, basically when you union 2 solids together the result is going to look from the outside the same as before, the only stuff that's been removed is all the extra inner structures.

Hope that makes sense! I can understand how it seems like the hole in a hollow tube is part of the object and so you're expecting it to persist during a union, but the way it works is when you have a hollow tube, it's only the thick wall that is really part of the solid, the hole in the middle is empty space same as empty space all on the outside of everything...

- Michael

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 From:  Involute
8492.9 In reply to 8492.8 
Jeez, that was so easy. I was differencing the tubes (to make a single hollow tube) and then unioning the result to the model, then deleting the surfaces that intersected the tube, which caused all kinds of problems, and I still couldn't get an opening in the inclined plane. Anyway, unioning the outer tube with the model and and then differencing the inner tube accomplished exactly what I wanted. I'm still learning to think like MoI, I guess. Thanks a lot.
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 From:  OSTexo
8492.10 
Hello Involute,

Have you considered running the pipe parallel to the long plane so you can blend the connection out at the bottom at a less acute angle?
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 From:  Involute
8492.11 In reply to 8492.10 
Thanks for the tip. At one point I thought I was going to have to put a sensor on the tube where it passes through the horizontal plate and wanted to preserve some space between the tube and inclined plane to accommodate it. Now I don't think I need it, but since I got the geometry to work as is I'm not going to mess with it. ;-)
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 From:  BurrMan
8492.12 In reply to 8492.11 
The Pipe2 command is here.

http://kyticka.webzdarma.cz/3d/moi/#Pipe
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 From:  Involute
8492.13 In reply to 8492.12 
Thanks, I found it. Slick tool!
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 From:  OSTexo
8492.14 
Hello,

A technique that gets you within the bounds of your cylinder and may be less restrictive on flow. I can't post the file because I'm out of space on the forum, but I could do a video if that would be helpful.

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 From:  Involute
8492.15 In reply to 8492.14 
Thanks for working on this, OSTexo. Aside from the fillets (which I just added; thanks for the idea), I'm not sure what you're doing. I won't impose by asking for a video. I have what I believe is a working solution for now. I don't think the flow will be a problem (the tube just has to pass a single M&M candy every few seconds). If it becomes one, I'll come back here and revisit.
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