Exporting STL files from 3D modelling software

How to export an STL file from 3D modelling software and settings to consider before exporting.

General CAD to STL process
After designing a model in a 3D modelling program, you save the design as an STL file. (Most 3D modelling programs have this function; if it doesn’t then these formats can be accepted also). An STL file renders surfaces in the 3D model design as a mesh of triangles. The number and size of the triangles determine how accurately your curved surfaces will be printed. You control the number and size of the triangles by setting the following parameters when you create the STL file from the 3D model design:

Chordal Tolerance/Deviation
This is the maximum distance between the surface of the original design and the tessellated surface of the STL triangle.

Angle Control
This is the angular deviation allowed between adjacent triangles. This setting enables you to increase tessellation, necessary for surfaces with small radii. The smaller the radii, the greater the number of triangles is required.

STL File Format
You usually have the option to save STL files in either binary or ASCII format. Binary files are smaller by a factor of 6, so this format is preferred. ASCII can still be accepted by our software, it just takes longer to process.

STL Geometry Check
We would recommend that you carry out an STL geometry check before submitting your model to us. Model designs containing holes and gaps have a negative affect on the quality of the printed model. Third-party software for this purpose attempts to fix the geometry of problematic files. This is a service that can be carried out by 3D Creation Lab which incurs an additional cost that is based on the number of errors in your model. The cost for carrying this process out will always be shown separately on your quotation once we have analysed your model.

Low resolution STL files

STL files describe a series of triangular meshes, and because of this they only approximate the high-level 3D model. The resolution used when creating the STL file determines how close the mesh matches the original model, so decreasing the size of the triangles increases the resolution of the mesh. A low resolution mesh becomes more apparent on non-planar surfaces, such as spheres. These become faceted rather than a smooth surface, as the picture below shows.

Sending us a low-resolution STL file may result in a printed model whose surface is rough. If you require a higher resolution then please increase the resolution before exporting the STL file.

As a general rule, models that have many contours and/or curved surfaces will require a much higher resolution than a flat model. A mesh resolution of 0.01mm to 0.03mm will generally produce a quality mesh. Reducing the resolution below this range does not necessarily mean that the model accuracy will be improved.

Confined Hollows
Models containing confined hollows will not be able to have the support material removed from them. Please bear this in mind when you are designing your models and ensure that the support material will be able to be removed. This is especially important when printing moveable parts in a model.

If you are designing a model with moving parts there needs to be enough clearance between the mating surfaces to allow the parts to have the support material removed and also to make sure they can move. Clearance between surfaces should be between 0.25 to 0.3mm (0.010 to 0.011 inches).

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