Partially split a solid with a surface

I would like to split a solid with a surface partially.
The final geometry is only one solid and there should be a line like a crack partially.
Is it possible in Rhino6?

Hello - like this?

NonManifoldMerge.3dm (49.7 KB)

NonManifoldMerge the plane and the box, then ExtractSrf and delete the outer bit if you don’t want it. Note this makes a non-standard object with a non-manifold edge and a slit in one or more faces…


Thank you very much. :slight_smile:
And I tried to export the modling as x_t or stp file but there were some errors. I think other programs don’t support this non-manifold objects. Could you tell me if you have this kind of experiece? Actually, I’d like to export this modeling as .stp file.

The surface has zero thickness. If you give the surface a small thickness (you can use OffsetSrf) then you will be able to make a valid object using booleanDifference.

Thank you for your answer.
I want zero thickness. If it is not avilable with zero gap, I’d like to know the reason.

You could intersect both objects to get the intersection curve? I’m struggling to understand the use case for this kind of object. What are you trying to achieve?

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My goal is to get one solid with a crack. The crack means a line on the solid which is splitted by one or serval surfaces partially. Because the each surface divides the solid partially, the solid still keeps one solid and the splitted area seems a crack.

Why does the box need to be split? What is the purpose if there is no thickness? Why not just intersect the two elements and get a line if you want to show it graphically.

This still doesn’t explain what you are trying to achieve. Is the

Purely a visual requirement? Or are you using it for manufacturing?

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It is for the FEM analysis for cacked solid medling. I will adust the crack lengh, depth and numbers. For this, I need seperated interfaces without thickness. I’ve tried this with other cad programs but I failed. So, I would like to know whether it is possible or not in Rhino. If it is impossibe, I think I would apply very small thickness which could be ignored for analysis.

Hello - as far as I can tell making the geometry you want is possible in rhino, the problem is exporting, is that correct? What formats are available, only Stp and x_t, in the target application? Mesh formats?


Yes. it is correct. The format I want is stp,step. I will import it in Abaqus. But when I export it in Rhino, Rhino says “STEP export does not support non-manifold objects. 1 non-manifold object was exported as a set of unjoined surfaces”

Right, Step will not work but are there other formats that the application will accept? For exmple you could mesh the objects in Rhino and export the mesh? Or can the application work with unjoined surfaces if the edges are in place (slit edge)?


If I can mesh the objects in Rhino, it would be fantastic. Actually, I tried it and I thought that Rhino only support 2D mesh, not volume mesh. So, I gave up. Is it possible to volume mesh in Rhino?

There are no volume meshes in Rhino, no.
Which file formats can Abaqus read?

Abaqus reads stp, igs, sat but I think stp,step are the best.

Step might be best, but doesn’t get the non-manifold objects across. IGES will export unjoined surfaces and leave it up to the receiving application (Abaqus in this case) to deal with that. Perhaps that might work.

… but for a crack to propagate, there must be an initial crack and all cracks have dimensions…
Depending on the overall size of your objects, you could model the thing in a Rhino document with units set to microns. I don’t know how Abaqus would deal with that, though…

I would try iges - if it sends the slit edges made by Rhino out, that might just do it.