A Systematic Survey of FDM Process Parameter Optimization and Their Influence on Part Characteristics <s> • <s> Fused deposition modelling (FDM) is a fast growing rapid prototyping (RP) technology due to its ability to build functional parts having complex geometrical shapes in reasonable build time. The dimensional accuracy, surface roughness, mechanical strength and above all functionality of built parts are dependent on many process variables and their settings. In this study, five important process parameters such as layer thickness, orientation, raster angle, raster width and air gap have been considered to study their effects on three responses viz., tensile, flexural and impact strength of test specimen. Experiments have been conducted using central composite design (CCD) and empirical models relating each response and process parameters have been developed. The models are validated using analysis of variance (ANOVA). Finally, bacterial foraging technique is used to suggest theoretical combination of parameter settings to achieve good strength simultaneously for all responses. <s> BIB001 </s> A Systematic Survey of FDM Process Parameter Optimization and Their Influence on Part Characteristics <s> • <s> Abstract Fused deposition modelling is a rapidly growing additive manufacturing technology due to its ability to build functional parts having complex geometries. The mechanical properties of a built part depend on several process parameters. The aim of this study is to characterize the effect of build orientation, layer thickness and feed rate on the mechanical performance of PLA samples manufactured with a low cost 3D printer. Tensile and three-point bending tests are carried out to determine the mechanical response of the printed specimens. Due to the layer-by-layer process, 3D printed samples exhibit anisotropic behaviour. Upright orientation shows the lowest mechanical properties. On the other hand, on-edge and flat orientation show the highest strength and stiffness. From a layer thickness and feed rate point of view, it is observed that ductility decreases as layer thickness and feed rate increase. In addition, the mechanical properties increase as layer thickness increases and decrease as the feed rate increases for the upright orientation. However, the variations in mechanical properties with layer thickness and feed rate are of slight significance for on-edge and flat orientations, except in the particular case of low layer thickness. Finally, the practicality of the results is assessed by testing an evaluation structure. <s> BIB002 </s> A Systematic Survey of FDM Process Parameter Optimization and Their Influence on Part Characteristics <s> • <s> Abstract The Additive Manufacturing (AM) technology initially was developed as a rapid prototyping tool for visualization and validation of designs. The recent development of AM technologies, such as Fused Deposition Modelling (FDM), is driving it from rapid prototyping to rapid manufacturing. However, building end-user functional parts using FDM proved to be a challenging task. The difficulty arises from the large number of processing parameters that affect the final part design such as: building direction, extrusion temperature, layer height, infill pattern and more. The processing parameters of FDM influence the quality of the parts and their functionality. In addition, a more systemic understanding is required to elaborate on the impact of the FDM processing parameters on the final part's mechanical properties, dimensional accuracy and building time. The presented paper provides an experimental study to investigate the independent effect of each processing parameter on the mechanical properties and dimensional accuracy repeatability of FDM parts. A total of 18 test specimen samples were printed using varying processing parameters. In order to investigate the repeatability and resulted tolerances, the dimensions of these specimens were measured and compared with a 3D CAD model. The presented work utilizes a tensile test per ASTM D638 standards to obtain the mechanical properties of each fabricated sample. In addition, the work provides a Finite Element Analysis (FEA) model for AM parts. The work suggested to simulate their behavior under mechanical loads for future investigation on the coupled effects of processing parameters. <s> BIB003 </s> A Systematic Survey of FDM Process Parameter Optimization and Their Influence on Part Characteristics <s> • <s> Fused deposition modeling (FDM), a well known 3D printing technology is widely used in various sorts of industrial applications because of its ability to manufacture complex objects in the stipulated time. However, the proper selection of input process parameters in FDM is a tedious task that directly affects the part performance. Here, in this work, the research efforts have been made to optimize the FDM process parameters in order to find out the best parameter setting as per the mechanical and surface quality perspectives by using hybrid particle swarm and bacterial foraging optimization (PSO–BFO) evolutionary algorithm. Taguchi L18 orthogonal array was used for the development of acro-nitrile butadiene styrene based 3D components by considering layer thickness, support material, model interior and orientation as a process parameters. Further, the relationships among selected FDM process parameters and output responses such as hardness, flexural modulus, tensile strength and surface roughness were established by using linear multiple regression. Then, the effects of individual process parameters on selected response parameters were examined by signal to noise ratio plots. Finally, a multi-objective optimization of process parameters has been performed with hybrid PSO–BFO, general PSO and BFO algorithm, respectively. The overall results reveal that the layer thickness of 0.007 mm, support material type sparse, part orientation of 60\({^\circ }\) and model interior of high density helps in achieving desired performance level. <s> BIB004
Build orientation: Build orientation is defined as the way to orient the part in a build platform with respect to X-, Y-, and Z-axes. In some papers, build orientation represented a quantitative parameter BIB001 BIB004 , but in others, it was considered a categorical parameter BIB002 BIB003 . Different build orientations are given in Figure 1 . • Extrusion temperature: The temperature at which the filament of a material is heated during the FDM process. Extrusion temperature depends on various aspects, for example, the type of material or print speed. Infill density: The outer layers of a three-dimensional (3D) printer object are solid. However, the internal structure, commonly known as the infill, is an invisible inner part covered by the outer layer(s), and it has different shapes, sizes, and patterns. Infill density is the percentage of infill volume with filament material. The strength and mass of FDM build parts depend on the infill density. • Infill pattern: Different infill patterns are used in parts to produce a strong and durable internal structure. Hexagonal, diamond, and linear are commonly used infill patterns ( Figure 2 ). Layer thickness: This is the height of the deposited layers along the Z-axis, which is generally the vertical axis of an FDM machine. Generally, it is less than the diameter of the extruder nozzle and depends on the diameter of the nozzle. Print speed: This is the distance traveled by the extruder along the XY plane per unit time while extruding. Printing time depends on print speed, and the print speed is measured in mm/s. Raster width: Raster width is defined as the width of the deposition beads ( Figure 3 ). It depends on the extrusion nozzle diameter. Raster orientation: This is the direction of the deposition bead with respect to the X-axis of the build platform of the FDM machine ( Figure 4 ).  There is limited research that optimized multiple parts' characteristics simultaneously. Further research on multi-objective process parameter optimizations can be another direction for future research. The FDM process is complex. It consists of several steps, and each step has different levels of uncertainty. Consistency of printed FDM parts can be improved by considering uncertainties during design and manufacturing. Additionally, it is also essential to incorporate the uncertainty of mathematical models and algorithms during analysis. • Toward a multi-disciplinary research direction, various machine learning algorithms and image processing may be applied for predicting part characteristics in the FDM process. Based on the findings of the existing works, some future directions and research gaps were identified for the FDM process. The authors of this review paper hope to encourage the general public to work together to reduce the research gaps in the FDM process, as well as simultaneously increasing FDM's employment in a wide range of industries, and FDM parts in the market. 