2.4.2 Classification of the Extrusion‐Based 3D Printing System 2.4.2.1 Hot‐Melt Extrusion 2.4.2.2 Cold Extrusion 2.4.2.3 Hydrogel‐Forming Extrusion
5 2.5 Selective Sintering 2.5.1 Working Principle, System Components, and Process Variables 2.5.2 Classification of Selective Sintering System 2.5.2.1 Selective Laser Sintering 2.5.2.2 Selective Hot Air Sintering and Melting
6 2.6 Inkjet Printing 2.6.1 Working Principle, System Components, and Process Variables 2.6.2 Classification of Inkjet Printing 2.6.2.1 Drop‐On‐Demand Inkjet Printing 2.6.2.2 Continuous Inkjet Printing
7 2.7 Binder Jetting 2.7.1 Working Principle, System Components, and Process Variables 2.7.2 Classification of Binder Jetting
8 2.8 Bio‐Printing 2.8.1 Working Principle, System Components, and Process Variables 2.8.2 Classification of Bioprinting 2.8.2.1 Extrusion‐Based Bioprinting 2.8.2.2 Droplet‐Based Bioprinting 2.8.2.3 Photocuring‐Based Bioprinting
9 2.9 Future Prospects and Challenges
2.1 Introduction
The advancement in technology greatly influences lifestyle and eating practices. The specific needs and dietary requirements made food scientists develop convenient processing technologies. One such approach is the 3D printing of foods that involves the layer‐by‐layer deposition of food material in a pre‐determined dimensions and shapes using computerized software (Kuo et al. 2021). 3D printing is an additive manufacturing (AM) process that is well established in many industrial sectors such as automobile, aerospace, fashion and designing, material science, construction, and medicine (Nida et al. 2020). However, applications of 3D printing in food manufacturing are under their initial growth stage that seems to be fascinating as well as challenging. In the food sector, 3D printing is recently gained potential research interest due to its novelty, convenience, creativity, efficiency, and flexibility (Jayaprakash et al. 2020). Since food is a complex multicomponent system, it possesses unique functional properties and characteristic behaviour to external treatments such as heating, cooling, mixing, and so on. Digitalization improves industrial production by implementing a novel design process thereby increases efficiency in both the manufacturing and supply chain (Baiano 2020). Thus, 3D printing is forecasted to be a revolutionizing technology that simplifies the food supply chain. 3D printing allows fabricating the foods as per the individual’s needs and requirements in a desired shape, size, colour, flavour, and nutrition. Also, 3D constructs with complex internal microstructures can be developed with greater accuracy and precision using 3D printing that are nearly impossible with conventional moulds (Mantihal et al. 2020).
The success of food printing depends on material composition, process conditions, and printing variables (Jiang et al. 2018). All these factors influence the final printability as well as edibility of the 3D constructs that makes 3D printing to be challenging when applied to foods. Hence, food printing is a multidisciplinary operation that requires knowledge of material science, software skills, mechanical as well as numerical controlling computer skills. In contrast to conventional food technologies, 3D printing allows the utilization of novel food ingredients and materials for the fabrication of foods (Derossi et al. 2020). As a characteristic feature, 3D printing uses uncommon protein sources such as fungi, algae, insects, buck wheat, and lupin seeds. As a sustainable technology, 3D printing utilizes the by‐products of the food processing industrial wastes for the development of value‐added sustainable foods for the future (Garcia‐Oliveira et al. 2020). However, the fuller potential of this emerging technology must be studied in detail to better understand the material behaviour. In this context, food printing technologies are one of the major considerations. As not all food materials are suitable for printing that requires appropriate pre‐processing that in turn depends on the specific printing technology. The present chapter provides a summary of various 3D printing techniques and their applications. As an initial attempt, the focus of this chapter is to streamline the available food printing technologies with their advantageous features and the different process variables that affect food printing. Thus, the present chapter provides a broad knowledge on the basic principle, mechanisms, and system components of food printing technologies that helps in better understanding and handling of food materials. Further, this work provides valuable insights in bridging up the gap in transformation of these lab‐scale techniques to industrial level.
2.2 Additive Manufacturing
3D printing is an additive process of developing a 3D construct from a digitalized CAD 3D design with the integration of a 3D printer with a computer. Most commonly 3D printing is used for rapid prototyping that allows testing the materials before practical implementation that has advantages like the use of lesser material resources, avoids wastage, saves energy, time, and cost (Shree et al. 2020). The higher degree of freedom of this technology allows its application to a diverse range of industrial sectors. In contrast to conventional manufacturing approaches, AM can produce goods with design personalization and mass customization. Ultimately, 3D printing could greatly limit the cost of processing with efficient utilization of resources and energy (Van Wijk and Van Wijk 2015). The basic working mechanism of a 3D printer is the printing of material in a pre‐determined design through appropriate conversion of digital CAD model into standard triangle language/ standard tessellation language (STL) (stereolithography [SLA]) file that initiates printing and controls the movement of coordinate axes. As discussed in the earlier chapters, the multi‐axis stages used in 3D printing can be of the cartesian, delta, polar, and scara configurations (Sun et al. 2018a). Among which cartesian and delta are the most used configurations in the manufacturing sector. The concept of 3D printing is the multilayer stacking of material along X, Y, and Z axes through precise control over material deposition. As a prototyping tool, the material deposition in 3D printing occurs through appropriate phase transitions and chemical reactions (Nachal et al. 2019). Based on the nature and type of heat source and the materials employed, there are several types of the AM process. These technologies are majorly used for plastics, polymers, composites, ceramics, and cement (Pradhan et al. 2021). The American Society for Testing and Materials (ASTM) framed different standards for AM and has classified processes into seven categories as follows