dual print simultaneously (Van der Linden 2015). One of the advantageous features of this particular design is its less floor space requirement and its ability to print larger‐sized objects. In contrast to other configurations, polar printers can rotate and move either forward/backward and sideways. The rare availability of this type makes them expensive as it costs more than twice as that of cartesian (Derossi et al. 2019).
The last type of 3D printer is SCARA which consists of rotating elbows that move in an arc (X and Y directions) while a separate motor is provided to assist the movement in vertical (Z) direction. The movement along the Z‐axis can be achieved by raising or lowering the printing platform (Sun et al. 2018a). In comparison with other configurations, SCARA is more compact and portable. An example of SCARA type is Sanna food printers equipped with eight food capsules with a temperature control unit and supported by an infrared panel for cooking printed food (Tan et al. 2018). But these systems suffer from the limitation of possessing expensive components that are not widely available as like delta and cartesian type that narrow down its use and applicability in food 3D printing.
In addition to the above context, based on the structural configuration, 3D printers are also termed as triangle structure (Prusa printer), triangle‐claw structure (Rostock printer), rectangle‐cassette structure (Ultimaker printer), and rectangle‐pole structures (Printrobot printer) (Yang et al. 2017). With these basic configurations, 3D printers are modified and adapted for food applications. In general, food 3D printing must address the following key considerations since food material is being printed, the entire components must be food‐grade; printer parts must be resistant to corrosion and should possess enough strength to wear and tear. Different printers have been studied for the printing of various food materials by several researchers. A commercial 3D printer Felix 3.0 originally designed for polymer printing was modified with a motor‐driven system and adapted for extrusion‐based food printing (Chen et al. 2019). Researchers used this modified system for printing soy protein gels and studied the effect of hydrocolloids on strength of 3D printed protein matrix. In another study, researchers were attempted to develop a multi extruder system that can be applied for printing 3D constructs from multi‐material which has precise control over material deposition. A commercial food 3D printer, FoodBot developed by Changxing Shiyin Technology Co. Ltd. (China) was modified in this study and used for dual extrusion of composite food gel (Liu et al. 2018). 3D printed edible circuits from bread substrate were developed from a commercial desktop 3D printer, BioBot 1 (extrusion printer) (Hamilton et al. 2018). Researchers are exploring the advancements of 3D printers for food printing by modifying the structure and design of commercial 3D printers. Likewise, many studies are being conducted for the applicability and suitability of materials for 3D printing in context with printing multi‐materials using multi‐head printing systems.
1.6.2 Components of a Typical 3D Printer
The basic components of a food 3D printer include printing movement arms, drive unit assisted with pulley mechanism, mechanical motors and feed rollers, material dispensing unit, temperature controlling system, printing head, printing platforms, and micro‐processing controller unit (Nachal et al. 2019).
1.6.2.1 Enclosure, Build Plate, and Guide Rails
Frames are the supporting structures that carry the print head and carriage arms. Supporting frames are made from metal sheets with acrylic covering provided with nuts and bolts. It supports all the other accessory components which influence the printer’s stability and durability (Horvath 2014b). Based on the type of configuration of the 3D printer, the carriage arms differ in design and movement. The printing movement of the delta configuration is illustrated in Figure 1.6. These arms are facilitated with a motion mechanism achieved by linear motion guideways incorporated with GT2 belts and pulley controls. Belts assists in the smooth motion of respective arms in X, Y, and Z directions. In the case of cartesian type printers, the assembly is equipped with threaded steel rods on which the nuts are mounted that assist movement upwards and downwards along Z‐axis (Huang 2018). The design of the print head varies with configuration type and it consists of a feeder system mounted with printing. The method of material dispensing also varies with the printing technologies and the description of which are explained in subsequent chapters.
Figure 1.6 Operation of delta type 3D printer. (a) Illustration of printing movements, (b), (c), and (d) pictorial views of printing movement following Pythagorean theorem.
Source: Derossi et al. (2019) / With permission of Elsevier.
Figure 1.7 Stepper motor and its controlling mechanism.
Source: From Derossi et al. (2019) / With permission of Elsevier.
1.6.2.2 Mechanical Drive Systems
Irrespective of the type of structural configuration, the carriage arms are connected with a mechanical drive system for assisting its motion along X, Y, and Z directions. The drive systems consist of stepper motor‐operated in a pre‐defined step of pulses (Figure 1.7). This step‐up mechanism aids in the rotation of printer arms in full degrees (Horvath 2014b). In general, the step‐up motors consist of a stator and rotor. Based on the structural configuration and working principle, stepper motors are of three types: permanent magnet stepper motor, variable reluctance stepper motor, and hybrid stepper motor. Among these, hybrid steppers are the most used stepper motors for 3D printing applications as it combines the advantageous features of permanent and variable stepper motors. Other characteristics that define a stepper motor includes its dimensions and rotating power (torque). The United States National Electrical Manufacturers Association (NEMA) declares a dimensional number to stepper motors named NEMA’s number based on the length and associated torque (Derossi et al. 2019). Apart from guiding the movement of carriages, stepper motors are also used for controlling the amount of material deposited during printing.
1.6.2.3 Microprocessor Controlling System
The motherboard is the heart of any 3D printer, responsible for coordinating the motion of components like the extruder, print bed, motors, and sensors. End stops are provided at all the carriages that act as sensors and allow 3D printers in identifying printing locations along the three axes, preventing it from moving past its limit otherwise it could result in hardware damages (Horvath 2014b). An interface arrangement of liquid crystal display (LCD) replicating rapid prototyper (REP RAP) full graphics smart controller is provided for controlling the printing process. Firmware refers to a set of computer programmes and instructions that connects the software with hardware (Horvath and Cameron 2015). The integration of software with hardware is detailed in the subsequent sections. A 3D printer with an LCD user interface can work as a standalone machine (using an SD card), i.e., it can be controlled without connecting to the computer. Although there are different kinds of user interfaces, the most common one is a basic LCD interface operated via a knob/dial. The printer can be operated with both LCD interface as well as universal serial bus (USB) assisted interface system connected with computer. Based on the working capacity and build size, the power requirement will vary. Often the printing process was carried out by connecting the printer to a computer via a USB cable. Files can be transferred and read either through an onboard controlling unit or through a USB
