Offset surface - simple task, bad result. what's wrong?

watch the folllowing video: rhinoerror.mov on Vimeo

thanks!

Hardware Overview:

Model Name: MacBook Air
Model Identifier: MacBookAir10,1
Chip: Apple M1
Total Number of Cores: 8 (4 performance and 4 efficiency)
Memory: 8 GB
System Firmware Version: 7459.121.3
OS Loader Version: 7459.121.3

Rhino 7 SR21 2022-7-27 (Rhino 7, 7.21.22208.13002, Git hash:master @ c31aea87137a5d0de449338a7ef6856f49dd4797)
License type: Evaluation, build 2022-07-27
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Apple macOS Version 12.4 (Build 21F79) (Physical RAM: 8Gb)
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Please post your surface as well. Thanks

Sure! Here you go. Thanks!

rhinoerror_os.3dm (159.2 KB)

Hello- offsetting with a tolerance of 1 when the distances involved are fractions of a unit is simply not going to work…

image

-Pascal

Hi @pascal , thanks for the reply. As you saw in the video (if you watched it until the end) I demonstrated the procedure with various tolerances like 0.001, 0.01, 0.1, and 1. thanks

edit: (and none of them work, as shown in the video)

Hi Julian - let’s just look at the cases that should work then… your blend has a radius smaller than the offset, which means that it will need to be consumed by the offset - it should make a hard corner there. With a smaller fillet it does do that; my guess is that the extents of that blend surface, which must be removed in the offset, compared to the offset distance, is too large. It looks to me like this is a somewhat special set of conditions that, yes, needs to be handled better…

-Pascal

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Thank you @pascal .
For me this is very important since I use Rhino for Binderjetting and SLS production. If I had to print the objects with an FDM printer, there wouldn’t be needed a wall thickness.
But since I need to send files to my production partner, I need to give the objects a wall thickness in most cases so small as 0.9mm.

The other workaround - meshing, OffsetMesh doesn’t work for me since the meshing in Rhino always generates bad results for me.
I am having this problem since five years now, I never found a proper solution. I used Meshmixer since it generates better meshes out of the rhino mesh and gives a thickness without errors.
But Meshmixer is discontinued and I don’t find any other solution than asking you for an idea. I hope you have one for me!! :slight_smile:

Hi Julan - in this particular case, it is not hard to fix (add and or trim the missing faces) ‘by hand’. Note, a fillet there - a rolling ball one - does allow the offset to work, I suppose because the setback is eveny distributed, so to speak, on each face, whereas your blend takes much more from the planar face than the cylinder. In any case, I will add your example to the heap.
RH-69801 OffsetSrf: cleanup fails

-Pascal