# Additive Manufacturing and Chemical Engineering: Looking for Synergies from a Bibliometric Study
## 1 Introduction  
Additive manufacturing, also known as 3D printing, has emerged as a revolutionary technology capable of manufacturing parts with complex geometries by adding material layer by layer based on information provided by a 3D model, thus granting extensive design freedom. This unique characteristic allows for the fabrication of complex or customized parts directly from the design without the need for expensive tools or molds, and reduces the necessity of many conventional processing steps. Complex parts, faithful to their design, can be manufactured in a single step without the limitations of conventional processing methods or commercial forms. Additionally, a significant reduction in the number of parts can be achieved by eliminating or reducing the need to assemble multiple components [1]. The origins of additive manufacturing can be traced back to rapid prototyping in the early 1980s, which culminated in the development of stereolithography (SLA) in 1984. The main difference between the two concepts is that rapid prototyping is oriented toward prototype creation, while additive manufacturing primarily focuses on the final parts for the user [2]. A key advantage of additive manufacturing is its ability to decouple design complexity from production cost [3]. This implies a revolution in product design across many sectors, which can leverage topological optimization, generative algorithms, and cellular structures to obtain optimized and high-value products capable of integrating complex assemblies into a single piece [4]. It is also perceived as an environmentally sustainable manufacturing technology, as it can potentially reduce up to 525.5 Mt of total carbon dioxide emissions by 2025 compared to conventional processes [5,6]. The process begins with the digital design of the component in the CAD software, which is subsequently converted into a suitable format, predominantly STL file format, for additive manufacturing. During this conversion, the component surfaces are tessellated into triangles, and a database of the triangle nodes is stored. From these data, two-dimensional layers are generated to determine the deposition of material at each level, while the deposition in the third dimension is determined by the thickness and interlacing of the layers. The geometric data of the component is then encoded in a file format, especially G-code, a programming language that provides the material deposition device the commands it must follow. The component is then constructed in a layer-by-layer manner, with the material of each layer interacting selectively with that of the previous one until the object is fully formed [7]. The precision of this process underpins the ability of additive manufacturing to produce intricate and highly accurate geometries. The field of additive manufacturing encompasses a wide variety of materials, processes, and devices that enable the creation of three-dimensional objects from digital models. However, this diversity also presents a challenge for the standardization of additive manufacturing technologies. To solve this problem, some categories have been established to group additive manufacturing technologies according to their common characteristics following the criteria of the ISO/ASTM 52900 standard [8]. This document defines seven standard additive manufacturing processes based on the type of material and initial physical form, deposition method, and energy or binding source (Figure 1). An important feature of additive manufacturing technologies is the need for suitable feedstock materials in the required form, such as powders, filaments, pellets, granules, sheets, and resins. The range of raw materials for additive manufacturing technologies is growing exponentially, and new materials are constantly entering the market [9]. The variety of materials that can be printed and the corresponding handling options have led to more than 50 different additive manufacturing technologies.