Issue link: https://wardsworld.wardsci.com/i/1507671
3 3D Printing (continued) + ward ' s science Although there are many different types of 3D printers on the market, the process of using a 3D printer generally follows the steps shown in Fig. 2. CAD modeling The user needs first to create a digital model using computer- aided design (CAD) software (such as TinkerCAD, Autodesk, or SolidWorks). The CAD model is then exported as an STL (stereolithography) file, which is currently the quasi-standard file format in the 3D printing industry. The STL file is generated by meshing the surface of the CAD model into triangles and storing the coordinates of the vertices of each triangle. The STL file format is limited to simple 3D printing because it contains only the geometry information of the surfaces and lacks color, texture, materials, and other 3D printing information. Because some advanced 3D printers can print with multiple materials and colors (for example, Stratasys J750), the Additive Manufac- turing File (AMF) format was developed by ASTM International and the International Standards Organization (ISO) as an inter- national standard. AMF is an XML-based format that has native support for color, materials, texture, and other features. Based on AMF, Microsoft® led an industrial consortium to develop the 3D Manufacturing Format (3MF) file format to streamline the 3D printing experience. Slicing Slicing is a step to cut the 3D model into many layers perpen- dicular to the print platform and convert the STL/AMF/3MF file into an intermediate language (for example, G-code, used in consumer 3D printers) to inform the 3D printer how to con- duct the printing process (that is, how to move the printhead). Depending on various slicing parameters (such as orientation of the model and infill pattern and parameters), slicing can have large effects on the final print, such as surface accuracy, mechanical strength, and build time. For models with overhang features, support structures are often needed to prevent the print from collapsing under gravity during the printing pro- cess—a parameter that needs to be carefully considered during the slicing process to minimize waste of support materials and postprocessing time. Category Typical Raw Materials Material Joining Mechanism Patterning Method Typical Commercial Machines Binder jetting Powder (plastic or metal) Use an inkjet printhead to jet liquid binders to loosely join the powder particles together and postsinter the powder particles in an oven. Patterning materials in 2D HP Jet Fusion 580; ExOne M-Print; Z-Corp Spectrum Z510 Directed-energy deposition Powder (plastic or metal) Use focused thermal energy (e.g., laser, electron beam, plasma, etc.) to fuse materials by melting as they are being deposited. Patterning both materials and energy in 1D Optomec LENS 450; DM3D DMD IC106 Material extrusion Filaments (plastic or composite or metal) or liquid paste Extrude materials through a nozzle or orifice in a semimolten or liquid state such that the materials can join together when they cool or dry. Patterning materials in 1D Stratasys uPrint SE plus; Makerbot Replicator+; Fab@Home Printer; Desktop Metal Studio System Material jetting Low-viscosity liquid resin or suspension Use an inkjet printhead to selectively deposit droplets of materials, then the materials are joined by polymerization or drying. Patterning materials in 2D Objet260 Connex3; Stratasys J750; 3D Systems ProJet MJP 5600 Powder-bed fusion Powder (plastic or metal) Use thermal energy (e.g., laser, electron beam, etc.) to selectively fuse regions of powder particles in a powder bed. Patterning energy in 1D 3D Systems ProX SLS 500; Arcam Q20plus; EOS M290 Sheet lamination Paper or metal sheets Paper or metal sheets are cut into patterns with a laser or CNC machining at each layer and joined together by adhesives or ultrasonic welding. Patterning materials in 2D Mcor Matrix 300+; Fabrisonic SonicLayer 7200 Vat photopolymerization Photosensitive resin Liquid resin in a vat is selectively cured by light-activated polymerization. Patterning energy in 1D or 2D 3D Systems ProX 800; Formlabs Form 2; Carbon M2 Printer Table — Major categories of additive manufacturing processes and their characteristic