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Offset surface of a complex geometry

Question asked by Mike Tree on Jun 22, 2014
Latest reply on Jul 10, 2014 by Chris Dordoni

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The attached part is representative of the blood volume within major vessels in the body. I am attempting to offset each of these surfaces by 1 mm, and then delete the blood volume, to re-create the actual vessel. I started with an imported .stl and used ScanTo3D to create the surfaces. I then filled the ends of the surface to create the current solid body. I hoped to shell outward, but it throws an error and highlights the faces unable to shell. So, I took the remaining faces and tried to offset the surfaces. I hoped I could offset most of the outer surface and then simply fill in the holes. However, that didn't work. I can offset some of the faces by selecting them one-by-one, but this is a VERY tedious process. Anyone have any suggestions?

Mike Tree Jul 10, 2014 11:40 AM

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Chris,

Though Geomagic was quick at offsetting the surfaces, I still needed to have my final part in Solidworks for other design purposes. Geomagic cannot export a solid part file that Solidworks can interpret so I would have to go back to the mesh stage anyway. So, I found how to offset a mesh in Solidworks. So, I no longer import the first mesh, transform in into a surface, and then offset that surface to get the second surface. Instead, I import the first mesh, offset a copy of that mesh (using Edit Mesh) and create surfaces from each of my two meshes (using Mesh Preparation Wizard and Surface Wizard).

Thanks for everyone's input.

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TCPC.SLDPRT.zip10.2 MB

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Jerry Steiger Jun 23, 2014 4:04 PM

Mike,

Blood vessels and bones and such are really hard to work with in SolidWorks. I'm afraid you are stuck with a very tedious task.

Jerry S.

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Chris Dordoni Jun 23, 2014 8:13 PM

Mike,

I looked at your file and as Jerry indicates, this will be a tedious task in SolidWorks. There are quite a few areas where the minimum curvature is smaller than the offset you want to make. This will require patching or rebuilding a significant number of the existing surfaces.

If you just have this one object, you could probably get through it with several hours of work.

However, if you are trying to establish a process for future work, it might be a good idea to look at some options .

What is the end use of the offset model?

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Mike Tree @ Chris Dordoni on Jun 24, 2014 9:05 AM

Chris,

Unfortunately I'm looking to do this on at least a handful of models. The model I currently have is extracted from some MRI images and is actually only representative of a volume of blood. I'm hoping to 3D print blood vessel models of constant thickness, so I'd like to offset the outer surface of the blood volume (inner surface of the blood vessel) to get the outer surface of the blood vessel. I will then remove the inner blood volume and will be left with a constant thickness blood vessel.

I originally imported the MRI data as an .stl mesh, so I could smooth the mesh more when I import. This just creates a trade off between the tedious work of patching and rebuilding surfaces and using a simpler surface. I intend to run fluids experiments on the models I print, so I'd like to keep as many features as possible because they will likely affect the fluid velocity.

I think my best solution is actually going to be using a different program (Geomagic) to offset the .stl surface BEFORE importing into Solidworks. Thanks for all of your help.

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Chris Dordoni @ Mike Tree on Jun 24, 2014 11:59 AM

With Geomagic, you can still end up with intersecting surfaces from an offset, or an offset that won't execute because the minimum curvature is smaller than the offset. However, it could be faster to repair these issues in Geomagic.

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Mike Tree @ Chris Dordoni on Jul 10, 2014 11:40 AM

Chris,

Thanks for everyone's input.

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Chris Dordoni @ Mike Tree on Jul 10, 2014 12:22 PM

Actually, Geomagic Studio can create nurbs solids from meshes. It fairly expensive so if you don't have the budget for it, you might be able to contract with someone that has it to do a conversion from a mesh to a nurbs solid that you can use in SolidWorks.

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6 Replies

Jerry Steiger Jun 23, 2014 4:04 PM
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Correct Answer
Mike,

Blood vessels and bones and such are really hard to work with in SolidWorks. I'm afraid you are stuck with a very tedious task.

Jerry S.
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Chris Dordoni Jun 23, 2014 8:13 PM
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Correct Answer
Mike,

I looked at your file and as Jerry indicates, this will be a tedious task in SolidWorks. There are quite a few areas where the minimum curvature is smaller than the offset you want to make. This will require patching or rebuilding a significant number of the existing surfaces.

If you just have this one object, you could probably get through it with several hours of work.

However, if you are trying to establish a process for future work, it might be a good idea to look at some options .

What is the end use of the offset model?
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- Mike Tree @ Chris Dordoni on Jun 24, 2014 9:05 AM
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  Chris,
  
  Unfortunately I'm looking to do this on at least a handful of models. The model I currently have is extracted from some MRI images and is actually only representative of a volume of blood. I'm hoping to 3D print blood vessel models of constant thickness, so I'd like to offset the outer surface of the blood volume (inner surface of the blood vessel) to get the outer surface of the blood vessel. I will then remove the inner blood volume and will be left with a constant thickness blood vessel.
  
  I originally imported the MRI data as an .stl mesh, so I could smooth the mesh more when I import. This just creates a trade off between the tedious work of patching and rebuilding surfaces and using a simpler surface. I intend to run fluids experiments on the models I print, so I'd like to keep as many features as possible because they will likely affect the fluid velocity.
  
  I think my best solution is actually going to be using a different program (Geomagic) to offset the .stl surface BEFORE importing into Solidworks. Thanks for all of your help.
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  - Chris Dordoni @ Mike Tree on Jun 24, 2014 11:59 AM
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    With Geomagic, you can still end up with intersecting surfaces from an offset, or an offset that won't execute because the minimum curvature is smaller than the offset. However, it could be faster to repair these issues in Geomagic.
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    - Mike Tree @ Chris Dordoni on Jul 10, 2014 11:40 AM
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      Chris,
      
      Though Geomagic was quick at offsetting the surfaces, I still needed to have my final part in Solidworks for other design purposes. Geomagic cannot export a solid part file that Solidworks can interpret so I would have to go back to the mesh stage anyway. So, I found how to offset a mesh in Solidworks. So, I no longer import the first mesh, transform in into a surface, and then offset that surface to get the second surface. Instead, I import the first mesh, offset a copy of that mesh (using Edit Mesh) and create surfaces from each of my two meshes (using Mesh Preparation Wizard and Surface Wizard).
      
      Thanks for everyone's input.
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      - Chris Dordoni @ Mike Tree on Jul 10, 2014 12:22 PM
        Mark Correct
        Correct Answer
        Actually, Geomagic Studio can create nurbs solids from meshes. It fairly expensive so if you don't have the budget for it, you might be able to contract with someone that has it to do a conversion from a mesh to a nurbs solid that you can use in SolidWorks.
        Like • Show 0 Likes0
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Offset surface of a complex geometry

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