Issue link: https://wardsworld.wardsci.com/i/1507671
4 3D Printing (continued) + ward ' s science Print Once the print file with the intermediate language (for example, a G-code file) is transferred to a 3D printer, the firmware of the 3D printer will plan the printing process based on the informa- tion supplied. One caveat is that even if the same print file is provided, the print results can vary among different printers or sometimes even from different locations in the build chamber of the same printer. In other words, repeatability is not guaran- teed. This is mostly because the printing process is an open loop and the printing parameters cannot be rigorously controlled throughout the entire printing process; for example, tempera- ture variation in space can lead to different printing results. Postprocessing After the print is finished, postprocessing is usually needed. This often involves removing the part from the build chamber (sometimes not trivial), cleaning the part, removing support structures, sometimes postcuring or sintering, and surface finishing. In stereolithography, for example, the print usually needs to be cleaned and rinsed with isopropyl alcohol (IPA) first and then postcured, because the liquid resin usually is not fully cured during the printing process. For processes that use powder particles, an entire powder handling system is usually needed to de-powder the part and avoid physical contact with the powder because of its health hazard. Postsintering is some- times needed to densify the part (such as for the binder jetting process in which a binder is inkjet-printed into a powder). The 3D printer A 3D printer turns a digital model into a physical object through the coordination of its subsystems and components. Although the workings of a 3D printer vary significantly from one to another, it generally consists of four subsystems, as shown in Fig. 3. The software system The software system is the "brain" of the printer that translates the digital model into instructions. CAD software helps design- ers express their idea in a digital format, which is then turned into a print file described by an intermediate language (such as G-code) that the firmware of the 3D printer can understand. The host software provides a user interface (UI), allowing the user to communicate and interact with the 3D printer through a computer or a mobile device. The firmware interprets the print file and translates it into instructions for the printer. The electronic system The electronic system is the "nerve" and "muscle" of the printer. The software instructions are in digital form and are not able to drive the motion system and printhead. Electronic controllers and drivers are usually needed to convert the digital instruc- tions into analog signals and deliver the signal and power needed to drive the motion and printhead systems. The motion system The motion system is the "arms and legs" of the printer that moves the printhead to the desired location at a specified time, based on software instructions. Motors generate rotary motion, and the drive system translates the rotary motion into linear motion in the x, y, and z axes. Belt drive and leadscrew (link- age) drive are the two most commonly used drive systems in 3D printers. Some printers also include encoders, which are the "eyes" of the printer to provide feedback on the position of the printhead for more accurate control. The printhead system The printhead is the "hand" of the printer that delivers energy and materials at desired locations at specified times. The func- tion of the printhead system is determined by the additive manufacturing processes. For example, the function of an inkjet printhead is to eject droplets, whereas that of a stereolithogra- phy printhead controls the pointwise scanning of a laser. The printhead in most 3D printers is controlled in open loop; that is, Fig. 2: Basic steps of 3D printing.