Several different additive fabrication processes are commercially available or are currently being developed. Each process may use different materials and different techniques for building the layers of a part. However, each process employs the same basic steps, listed below.
1- Create CAD model: for all additive processes, the designer must first use Computer-Aided Design (CAD) software to create a 3D model of the part.
2- Convert CAD model into STL model: each form of CAD software saves the geometric data representing the 3D model in different ways. However, the STL format (initially developed for Stereolithography) has become the standard file format for additive processes. Therefore, CAD files must be converted to this file format. The STL format represents the surfaces of the 3D model as a set of triangles, storing the coordinates for the vertices and normal directions for each triangle.
3- Slice STL model into layers: using specialized software, the user prepares the STL file to be built, first designating the location and orientation of the part in the machine. Part orientation impacts several parameters, including build time, part strength, and accuracy. The software then slices the STL model into very thin layers along the (X,Y) plane. Each layer will be built upon the previous layer, moving upward in the Z direction.
4- Build part one layer at a time: the machine builds the part from the STL model by sequentially forming layers of material on top of previously formed layers. The technique used to build each layer differs greatly amongst the additive process, as does the material being used. Additive processes can use paper, polymers, powdered metals, or metal composites, depending upon the process.
5-Post-processing of part: after being built, the part and any supports are removed from the machine. If the part was fabricated from a photosensitive material, it must be cured to attain full strength. Minor cleaning and surface finishing, such as sanding, coating, or painting, can be performed to improve the part's appearance and durability.