# A Review on Recent Trends and Applications of IoT in Additive Manufacturing
## 1 Introduction  
With the advent of mechanized production methods in the latter half of the 18 th century, the era of the industrial revolution began. The rigorous research works and application of scientific trends led to several technological advancements and ran towards the optimization of things. Industry 4.0 is the new name for the 4 th industrial revolution, which is projected to bring significant improvements to industrial sectors. It integrates physical and digital technologies, such as analytics, robotics, AM, artificial intelligence (AI), sophisticated materials, natural language processing, high-performance computing, argument reality, and cognitive technologies. Thus, in an Industry 4.0 factory, machines are connected as a collaborative community. Such evolution helps to utilize advanced prediction tools, integrating the IoT with various manufacturing processes, so that data can be systematically processed into information to explain uncertainties, which can thereby support more updated decisions [1]. The IoT is the foundational technology that is accountable for the idea of Industry 4.0. This technology enables the logical linking of all the equipment and methods associated with the production environment, sensors, productioncells, transmitters, computers, the production planning system, strategic industry guidelines, government information, and climate, and everything is recorded and analyzed in a database [1; 2]. The Internet of Things is a commonly used name for a set of technologies, systems, and design concepts linked with the coming wave of internet-connected physical objects. Machine-to-machine (M2M) communication connects sensors and other devices to information and communication technology (ICT) networks via wired or wireless connections. IoT is different from M2M in that it also includes connecting these systems and sensors to the wider internet and using general internet technologies [3]. In the long run, it is expected that an IoT ecosystem will develop that is similar to the Internet we have today. This will allow things and real-world objects to connect, talk to each other, and interact with each other in the same way that people do today on the web. A deeper understanding of the complexity of the systems in question, economies of scale, and strategies to assure interoperability will lead to the wider acceptance and implementation of IoT solutions if combined with essential business motivations and governance frameworks throughout value chains. One of the major and upcoming revolutions in the industry is integrating IoT with AM [4]. Today, we have been seeing several advancements in this area of integration, where practical models and several ongoing research works are processing out. Almost seamless integration has occurred between additive manufacturing and the Internet of Things, and given that they are both cutting-edge technological breakthroughs, their merger was nearly inevitable. In this part of integration, we found that electronic device prototypes, such as GPS systems and circuit boards, may be created via 3D printing. This capability is being leveraged by businesses worldwide. Israeli start-up, Nano Dimension, for instance, has devoted itself to developing a 3D printer capable of producing circuit boards for the Internet of Things [5]. AM plays a vital role in Industry 4.0 and it is an innovative manufacturing technology capable of fabricating geometries in almost all shapes even with small cellular structures inside, by adding material layer-by-layer directly from the digital data file [6]. The material used to create the solid object makes these AM devices different. It uses materials like polymers, metals, thermoplastics, ceramics, composites, sand, bio-chemicals, and also some other type of materials [7; 8; 9]. However, the use of metal alloys in AM is restricted to a few components due to various reasons like input parameters, fixed bed size, availability of filler materials with respect to applications, etc. [10].