3D Printing of Foods. C. Anandharamakrishnan

are grouped as XY head printers, XZ head printers, and XYZ head printers. In the former type of XY head printer, the print head moves in the XY plane, and the print bed moves in the Z plane. Another variation in print head is ‘XZ head printers’ where the print head moves in XZ plane and the print bed moves in Y plane, respectively. An example of this type of printer is Choc creator, a commercial 3D food printer specifically designed for the customized fabrication of 3D constructs from chocolates. The third case is ‘XYZ print head’ where the print bed remains stationary and only the print head moves in all directions as in the case of Foodini, a commercial 3D printer developed by Natural Machines (Derossi et al. 2019). Comparatively, the motion of XY and XYZ head printers remains faster than that of XZ head printers. However, this type of cartesian printer requires accurate and regular calibration before printing.

Figure 1.4 Value chain of 3D food printing. (a) consumer buying 3D printed foods; (b) consumer buying 3D food printer.

      Source: Jayaprakash et al. (2019) / With permission of Elsevier.

Figure 1.5 Illustration of printing movements in various printer configurations. (a) Cartesian; (b) Delta; (c) Polar; (d) SCARA.

      Source: Sun et al. (2018b) / With permission of Elsevier.

      The second type is the delta 3D printers works on the triangular coordinate mechanism based on the Pythagoras theorem with relative movement of printing arms in three co‐ordinate axes (X, Y, and Z directions) (Sun et al. 2018a). These types of printing system consist of three pairs of carriages (arms) that moves simultaneously up and down and aids in printing with a stationary print bed. Here, each pair of arms form the diagonal of a triangle and makes an angle to other planes namely X and Z. Likewise, all the three carriages move at the same time thereby aids in simultaneous printing. The major advantage of the delta type over the cartesian is its higher printing speed because of less physical loads and its ability to print bigger‐sized objects especially in the Z direction (Horvath 2014b). However, this suffers from the limitation of low precision in printing smaller objects.

      Another configuration of the 3D printer is polar which is the rarest that works based on the polar coordinate system. Here, the motion of printer arms is defined by an angle of 360° with a pre‐defined centre point along radial direction while printhead moves vertically up and down thereby forming a 3D construct (Sun et al. 2018a). An example of this type of configuration is the XOCO 3D printer, a commercial chocolate printer equipped with a rotating build plate with a single supporting pillar that holds a print head and glass covering (Ontwerp 2018). Another example for polar configuration is the TNO food printer that consists of three rotating arms provided with a pair of material cartridge facilitates 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: