It’s easy to create a three-dimensional object with a CAD program.  But to build that three-dimension object with 3D printing/additive manufacturing will require a special three-dimensional file. Several exist including AMF and 3MF.

The Standard Triangle Language (STL)* has been around for more than 30 years and is still the most common file format used for 3D printing.  Briefly, what you design in CAD is converted (translated) into triangles in a 3D space.

The STL program encodes the surface geometry of an object using “tessellation.” Tesselation tiles a surface with geometric shapes, usually triangles. Much feature information is stored in these triangular geometries that a 3D printer uses to build the design.

The triangles follow a few rules. For example, adjacent triangles must share two vertices.  The right-hand rule is used to ensure the that the vertices are orientated with the normal vector.

Nearly all CAD programs today have a feature to export a design into an STL file and set the desired STL resolution.  Just keep in mind that you will not get a good print if the export quality is poor.  The illustration below gives you an idea of STL file resolution, ranging from very high to very low.

Either resolution extreme can be a problem for 3D printing.  A low-resolution file will result in a print where the surface finish is not smooth.  For rough prototyping, this may be fine, but for a more finished product, you will need a better resolution.

A very high-resolution STL file will consist of so much data for the 3D printer to process that you may have a print fail.  If the 3D printer is not brought to its knees, then such a high resolution will increase the time it takes for the printer to build the design.

An advantage of STL is that it is a universal file format compatible with all 3D printers.

 

*At various times in its long life, STL has been an abbreviation of the word Stereolithography, or stood for Standard Triangle Language, and Standard Tessellation Language.