Manage and export valid 3D files for 3D printing from Catia V5

While it is always easier to model directly using the right dimensions, thicknesses anddistances, it is sometimes necessary to measure parts of an existing volume. CATIA has two tools: Absolute measurement and relative measurement.

“Measure” tool

The relative measurement tool calculates the distances between any type of geometry: points, lines, planes, surfaces … The minimum distance is displayed. This tool measures either the distances between different bodies or simply a distance between different geometrical elements of a single body.

“Absolute measure” tool

The absolute measurement tool provides all the necessary information on a volume or a surface. It also helps with the “thickness measurement” to measure to a thousandth of a millimeter and very intuitively and quickly any thickness / length. In the case of a preparation of your CAD for 3D printing, absolute measurement tool will be used primarily to obtain volume information.

For dimensions, it is important to note that the concept of units is not valid for CATIA here. When exporting the file in a format other than native CATIA (.CATPart), the units are not retained. You’ll need to define the unit and scale appropriately when you move to the Sculpteo interface.

“Tesselation” tool

This is the “tesselation” tool that allows you to generate the mesh. It is located in the sidebar.

You can then work on two main features, which will determine the accuracy of your model: sag and step.

The sag is the maximum distance between the mesh and the real shape. “Step” meanwhile corresponds to the distance between two neighboring nodes. Since both are dependent each other, the default setting for step is ‘disabled’. You choose on what basis you want to control the accuracy of your model’s mesh.

We recommend that you keep the default setting and use the sag. Finally, note that the lower the values you choose, the more accurate your mesh will be, and of course heavier to export. Also note that the accuracy of the machines being one micron, it is unnecessary to enter a sag of less than 0.01mm.

Finally you can choose the grouped or separate option. If you have several pieces, the “grouped” option generates a single mesh for all parts. Conversely, choosing “distinct”, CATIA generates independent mesh for each body part. Note that the mesh appears in the product / part which is activated in the tree.

To view the mesh, which is not the default view, you need to access the mesh properties that appear in the tree (right click > properties display mode, check “triangles”).

“Mesh regeneration” tool

This tool allows you to automatically re-mesh the model. This can be useful if you have a complex shape to mesh.

General information

An “Information” icon that informs you about the geometry of the mesh can be found at the bottom of the toolbar.

Automatic error detection

Once your mesh have been generated, you can use the “mesh cleaning” tool in the side toolbar. This tool is quite limited as it merely permits errors detection. We will see in the next chapter how to fix them. The following window will appear. Click on “analysis” to see if your model contains errors or not.

The mesh cleaning tool allows you to detect basic errors such as duplicated triangles, bad direction, edges and non-manifold vertices. A drop-down menu in front of each of the above errors allows you to assign a color to better identify the problem.

You can also apply filtering options of long edges and small angles, entering the values you want. Then clicking “apply”, affected points or edges related to the problems identified will be removed, as shown in the images below.

Also note that the “structure” tab will allow you to manually change the orientation of your surfaces (We will explain this more precisely in the next chapter).

CATIA works on a system of NURBS, which therefore allows you to easily save your model in STEP or IGES format. To do this, simply select one of these formats in the menu at the time of saving.

It is also possible, at the time of export, to convert your model to a file defined by a mesh, such as STL. It is indeed the most widely used format for 3D printing. Although CATIA does not directly support mesh modeling, you can generate one while exporting, which makes CATIA especially effective for 3D printing. CATIA allows import and export in this format, with quite a range of settings.

To export your model, you go through the STL rapid prototyping workbench (Start tab > Machining) or the Digitized Shape Editor module (Start > Form tab). The first workbench will be useful if you want to prepare your CAD model for 3D printing, while the second is more oriented towards processing point clouds from a 3D scanner. Both are quite similar except for a few tools.

Export is achieved by using the “STL export” button in the side toolbar.

If your design is an assembly, several options are available to you when exporting. If you generated one mesh per part, then you can get a .STL file for each part. To do so, click on the icon “STL export.” Then click successively on the different meshes forming your assembly, and choose the “distinct” option. If, however, you want to get a single .STL file for your full assembly, then choose “grouped”. But be careful, “grouped” doesn’t mean “merged”. It just means that you will have only one file for the whole assembly.

Some files, by their complexity or nature, will not be optimal candidates for export to .stl. They will generate either very large files (over 500MB), or simply not be exported from CATIA below a certain level of accuracy.

Files with many curved / rounded parts or large areas based on vector drawings with a large number of points (text, graphics, etc.), will generally generate very large files in .STL.

It would be better to export them to a “vector” IGES or STEP-type as mentioned above. These file formats are obviously supported on our website.

Before starting this chapter on repairing the most common issues when preparing your data for 3D printing, here is a description of some tools that will be useful later.

“Activate” tool

This tool allows you to select the mesh points you need to work on. You will be able to use conventional tools such as the selection tool or brush. The neighborhood tool lets you choose a whole part of a mesh, selected automatically by CATIA depending on your mesh geometry. Finally, the “pointing” mode will allow you to select items one by one, which is great for detailed touch-ups.

You can also choose to work at different levels: points, triangles, cloud, etc.

Translation / Rotation / Symmetry / Scale tools

You will find them in the “digitized shape editor” workbench. Their use is identical to the one you know in Part Design.

The size of the mesh depends directly on your export settings and of course the complexity of your model.

Some functions, such as the leave and text functions (based on a highly vectorized initial design) are particularly resource-hungry and will quickly increase the size of your exportedfile.

If your file is too large to be imported on Sculpteo, try lowering the level of detail specified in CATIA (or no arrow), or if your model incorporates many holidays / rounded or curved parts / sketches based on text or graphics vectorized, try to export in a more appropriate format for the file type, such as iges or step.

Overall mesh reduction

CATIA also provides a “decimate” tool, which reduces the number of triangles in the mesh. This tool should be used with caution, since reducing the number of triangles also reduces precision. This tool gives as much control as possible for the reduction of triangles, with several options:  

• Minimum length: This option allows you to keep maximum control while returning the minimum edge length you want. When you choose this option, a green sphere appears, allowing you to compare the size you selected with the size of your model. With this option, the edges whose length is greater than the value that you choose will not be changed, the mesh remains the same in non-affected areas.

• Targeted percentage: This is quite a random setting to reduce density to a defined percentage of triangles. The reduction can therefore be very fast, but without much predictability of the result. The mesh is usually completely changed.

Local mesh reduction

If you want to change only a part of the mesh, you can use the selection tool “activate”. It offers several selection modes such as the ones we mentioned previously (brush or hatch., trap…). Choose the mode that suits you, select the area to decimate, and click OK. Then apply the “decimate” tool on the active area as seen above.

To get back to the rest of the mesh, click the “activate” tool again, select the mesh you were just decimating, click on “swap” and finally click on “activate all.” You will then get a full mesh with locally depleted zones.

“Fill holes” tools

“Fill holes” is quite an efficient tool, offering many settings that can solve most cases of non-watertight meshes. To do this, click the icon located in the sidebar, the holes are then detected and a window opens with several options:

• The “hole size” allows you to select only the holes whose size is less than the value you have entered.
• The “points insertion” to select the arrow and / or the pitch of the mesh that will be generated for filling the hole. Again, the higher this value, the higher the precision of the mesh.
• Finally, the “shape” is useful for filling unflat surfaces. Do not hesitate to move the cursor position up for good continuity in the reconstruction.

Before validating and generating the filling surface, select or deselect with a single click, holes that will be affected by the repair. Green holes will be repaired, red ones will be ignored.

Then check the result of the reconstruction by performing a “zoom in” on the area to ensure the continuity of the surface generated with the initial surface is good. If necessary, repeat the operation by reducing the arrow and / or the not.

« Smooth » tool

This tool, which is represented by an iron in the toolbar is very easy to use. Just select some or all of your mesh, and each time you click on “apply” a smoothing operation will be performed. The more you repeat the operation, the smoother it becomes. After a number of operations, the algorithm plateaus and becomes less effective.

« Mesh offset » tool

If you forget to generate thickness of one or more surfaces in your model in the GSD workbench, it is always possible, even after your meshed model has been created, to generate thickness.

To do this, use the “mesh offset” tool, enter the value of the thickness, and remember to check the option “create the shell” to generate a closed body.

« Rough offset » tool

This tool allows you to precisely control the shape and quality of the shell you will generate. Click on the icon “offset distance”. A black arrow represents the length of your shift and its direction.

The setting on the granularity directly affects the quality of the mesh of the generated shell. The higher is the granularity, the lower the accuracy (left image). Conversely, a high granularity will reduce the size of your exported file (right image).

Finally, the 3 direction icons allow you to control the shift.

As mentioned earlier in the tutorial, the orientation is especially important for the volume to be valid for 3D printing because it helps to determine the inside and outside of the shape.

If your body is a solid body in CATIA, you will not have any problem. CATIA allows only the creation of “consistent” solids.

If your body is a surface body, the orientation of the mesh is automatically managed by CATIA during creation. You can see it in the “mesh cleaning” tool “structure” tab and then selecting“orientation”. You can then reverse the orientation of certain faces if necessary by clicking the corresponding arrows. In the unlikely event CATIA generates errors during export (complex files), the Sculpteo auto repair tools will be able to repair it automatically because the bodies generated by CATIA are easily adjustable.

CATIA operates on a principle of NURBS, so the generation of triangles occurs only once the mesh is generated, or when exporting. In both cases, the orientation of the triangles is uniform, and there are usually no problems.

Nevertheless, it is possible to use the “mesh cleaning” tool to check that everything is in order. Go to the “structure” tab, check “orientation” and see if blue areas appear on your mesh. If so, click on each of the arrows on the inverted triangles (blue), which then become yellow and click “apply”. The affected triangles will be automatically flipped.

Automatic “Mesh cleaner” tool

Run a scan with the mesh cleaning tool, which notifies you of any non-manifold edges or points. If you are in the “suppression” tab, click “apply”. Errors are suppressed but can sometimes leave holes in your mesh.

Don’t hesitate to run several successive analyses since removing points / edges in the first analysis, can lead to the creation new points / non-manifold edges in a second analysis.

You can then fill using the tool “triangle creation” or “fill holes”. If the repairs are fast, use the tool for creating triangles, you will then have to click successively on two edges to form a triangle, which appear in a blue color on your mesh.

Manual cleaning : “Delete points” tool

If you want to manually repair errors, be aware that there is a “striking points” tool in the digitized shape editor workbench. You just have to click the point to delete it, and click “apply”. Points and their related edges will be removed.

In case there would be many holes, prefer the automatic hole filling tool

Self-intersections do not generate problems for export, and conversion to STL can take place regardless. It is only when printing that trouble arises. You will need to make sure your surfaces do not overlap. The following tools will therefore help you to precisely select surfaces.

“Cut” tool

This tool has exactly the same features as the “activate” tool. The difference is that when you click OK after defining the area of interest, the latter is separated from the rest of the mesh. You then get a CutMesh.1 and CutMesh.2 tree that correspond to the selected area and the unselected area.

“Trim/split” tool

This tool is the same as the cutting tool in GSD. First selecting the mesh that has to be cut, then the cutting element (which may be a plane, a surface or another mesh). You now have two new elements in the tree. By checking “Overview”, a white line representing the cut appears on the mesh.

“Merge meshes” tool

This tool allows you to merge two or more meshes. It is useful when you want to, for example, assemble two meshes on which you want to make a cut or perform any cutting operations.

Multi-shell files are automatically handled by CATIA. You can choose to keep the different bodies at export, obtaining an .stl file for each body, or export a single .stl file containing all the bodies. In both cases, CATIA generates a file ready for 3D printing.

To repeat 3D prints (multiple copies of the same model), the most economical method, is to use the online Sculpteo tool which creates a series or batch (of at least 20 pieces), which will optimise the positioning and price of production.