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How to Convert Graphics to Solid Body in CATIA

This tutorial demonstrates how to convert a Stereolithography Mesh (.stl) graphics object to solid editable body in CATIA V5. This is useful when we require to modify an STL object file in any CAD processing tool, such as, AutoCAD, Autodesk Inventor, SolidWorks, CATIA, and so forth. It is also important when we plan to do a Finite Element (FE) analysis of an object that is available only in the STL format. For the demonstration purpose, this tutorial uses an STL image of an anonymous patient having Scoliosis, which is available online. You can download the file from this site.

Processing an Image in CATIA

At first, open CATIA V5, then go to 'Start' and select ‘Shape’, then choose ‘Digitized Shape Editor’. See the screenshot below for the process.

Opening CATIA V5 Digitized Shape Editor




















After that, in the following window, just click ‘ok’ to create a new part file.

Creating Part in CATIA V5 Digitized Shape Editor




















We will now import the (.stl) by clicking the ‘Import’ option as highlighted below.

Importing a STL file in CATIA V5


















Next, click ‘Apply’ and then select ‘ok’ to import the (.stl) file, which looks like below:

Importing a STL file in CATIA V5




















Since, we have imported an STL file from third-party source, we need to check the quality of the image, and clean it up. There is an option ‘Mesh Cleaner’, click it, and the following window will appear.

Mesh cleaning in CATIA V5


















A pop-up small window will appear. Select the object, and then click ‘Analyze’. Click on the ‘Isolated Triangles’ option, and change the color, so that you can visualize it clearly. In this case, we see it is yellow.

The process of removing corrupt meshes from the STL file in CATIA V5



















As you notice that we are in the ‘Deletion’ mode of the ‘Mesh Cleaner’ window. So, we need to delete those unwanted or corrupted triangles to make it a valid solid body. Otherwise, the conversion either might fail or proceed, but in that case with lots of corrupt meshes that will hamper your analysis.

As we see, there are 60999 corrupt triangles, which need to be discarded. This may also remove some parts from the image, but if that part is not significant, then it may be alright to proceed depending on our requirement. We just need to make sure that we have our concerned region unaffected for the analysis. Next, click on the ‘Long Edges’ and continue the same process for removing the corrupt regions. The last option is the ‘Small Angles’, which we need to select and click ‘Apply’. 

The process of removing corrupt meshes from the STL file in CATIA V5



















After the process is done, the following window will appear. We see that there are three ‘Non-manifold Vertices’ that need to be removed as well in a similar way.
We need to continue the mesh cleaning process at least twice to make sure that we have removed all the corrupt segments. After doing so, we will have the following image without the unwanted meshes.

The process of removing corrupt meshes from the STL file in CATIA V5



















Next, we need to click on the ‘Structure’ tab and subsequently, click on the ‘Orientation’, and ‘Split in Connected Zones’ options to check the followings. If the color for the ‘Orientation’ stays same, as in this case, ‘Yellow’, then we are good to go. For the ‘Split in Connected Zones’, there should be nothing specified in the window as highlighted by the following two screenshots below.

The process of removing corrupt meshes from the STL file in CATIA V5











The process of removing corrupt meshes from the STL file in CATIA V5


















After the above process, we need to click Start > Shape > Quick Surface Reconstruction. The steps are depicted below.

Surface reconstruction process in CATIA V5


















Next, click Insert > Surface Creation > Automatic Surface. Just follow the following instructions shown by the image.

Surface reconstruction process in CATIA V5


















The following window will appear. Try to keep the parameters same as shown in the tiny popped-up window. Then, hit ‘ok’.

Surface reconstruction process in CATIA V5 and selection of key parameters


















We are almost done in creating the Solid Body. After the automatic surface creation, we need to close the surface, which is depicted below. Click Start > Mechanical Engineering > Part

Closing the surface after reconstruction in CATIA V5


















Then follow this sequence: Insert > Surface-Based Features > Close Surface.

Closing the surface after reconstruction in CATIA V5


















We are all done. Finally, we need to save it as a 'CATIA part' file and also export it to (.igs) format in case if somebody wants to perform FE analysis.

The final reconstructed 3D solid body ready for further modification


















The following image shows the closed view of the processed solid 3D Scoliosis skeleton that may be used for any analysis that needs geometry manipulation. 

Reconstructed 3D Solid Body in CATIA showing the Scoliosis Skeleton

























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