Create solid from complicate polysurface

Is there an easy automated way to create a 3d solid from the attached polysurface?
The offsetsurf is not able to do it.
membrane.3dm (483.8 KB)

Hi Ar00302,

you can duplicate the border edge, use setpt command to flatten it and extrude passed the original border edge and trim, so 3 commands + cap at the end will give you a closed solid. I also used merged coplanar faces tool to clean up the trimmed surfaces at the end but you don’t really need to.
membrane_solid.3dm (616.9 KB)
I’ve attached the result.

Sorry, my description wasn’t correct.
I want to thicken this polysurface by about 0.005 m.
The result should be like this (this is actually a previous version)
membrane_solid_result.3dm (1.1 MB)

It just took me too much to model this, and I wonder if I missed something and if there is an easier way to update the new polysurface because I have made some changes.

ahh ok I see what you mean, you would most likely have to do it manually in Rhino, I through it in SW and it does a much better job you just need to trim away some excess parts that extended past the base border edge but only takes a few mins. I used .005M thickness

(upload://rBVBNOYjjgaXUMHdlhBwKN5ghaz.3dm) (1.1 MB)

membrane_offset.3dm (1.1 MB)

That’s exactly what I want to achieve but in the opposite direction. By SW you mean solidwork? I’ve done it once manual and I spend too much time.
Thanks anyway.

Yep solidworks, as much as I love rhino there are certain tasks I would leave to a solid modeler especially if it needs multiple changes its a lot easier to update them in a parametric environment.
EDIT: sorry there was a corner I forgot to fill in here’s the correct file:
membrane_reverse_offset_corrected.3dm (1.1 MB)

I also tried this with Microstation which if I am correct has parasolid kernel same as SW and the result was much more like rhino offsetsrf. You use offset surface in SW?

In SW its call “thicken” which takes a surface body and thickens it into a solid body.

your document-tolerance is 0.001 - which is quite close to a 0.005 offset.
you can set it to 0.0001 - which is in better ratio to 0.005m offset. (which is not recommended as a general workflow) - but the offset works here - see attachment inside and outside.

in general you should start modelling with the necessary tolerance from the beginning.

Uploading: Screenshot 2022-05-22 at 00.05.06.png…

membrane_offset.3dm (5.8 MB)

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I have tried to increase the tolerance with no luck.
But I never it to 0.0001. I tried with 0.000001.
What I also see in your model is the use of rounded corners.
I use sharp corners and the result is not good.
Rounded corners actually, work, but only with tolerance set to 0.0001. If I increase eg 0.00001 or 0.000001 it produces naked edges.
Strange. Very strange. But thanks.

i did not dig into all details of your model.
but general - from a geometric point of view - if 4 or more surfaces meet in one corner (x) the offset surfaces do not (always) meet in a single corner anymore - this will cause problems.

see a simple example in the screenshot.
how should a sharp offset look like for this geometry ?

Is this part of my model? If not can you attach your example file?

the above is just a general geometric example to show that offsetSrf with sharp is not always solve-able in unique way if 4 surfaces meet in one corner. … ok i dig deeper into your geometry:

looks like a bug to me:
a simple box with a rip does not _offsetSrf (option sharp) anymore, as soon as some surfaces are deleted / the polysurface is open.
(Version 7 (7.19.22137.07002, 2022-05-17) mac os x)

(file in initial post is away from origin and tolerance is critical)
but this a easy to repeat error:
small objects millimeter.
planar closed PolySurface in Right view
_extrude (solid yes)
_offsetSrf (5mm) works (green)
delete some faces
_offsetSrf (5mm) fails (red)

offsetSrf_bug.3dm (286.1 KB)

hope this is repeatable - kind regards -tom

you are right it’s complicated for 4 surfaces as they don’t meet at one point.
The result should be something like this
4 surf.3dm (115.0 KB)
But in my case, I don’t think I have 4 surfaces meet at one point.

Away from the origin? Do you mean 200 m is away from the origin in general?
@Ryan656 solution using Solidworks give the expected results.

Could you provide the uncorrected file that solidwork produces?
Without your fine edits.

also if you try this file which @Ryan656 made in the sec post the offset command with sharp edges still fails in an area. But obviously the result is better. So that’s at least a workaround.

you should have something like 9 or even 10 to 12 digits to work with
200m and a tolerance of 0.0001 should work for a command without a bug -
But i tried to narrow the error down as much as possible.

Hi Ar,

You mean just the surface body out of SW?

Here’s the surface out of SW as well as the previous result I showed you in parasolid format:
membrane.x_t (159.0 KB)
membrane_reverse_offset.x_t (329.4 KB)

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