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In this paper, a novel boundary element formulation for the deformation of a viscous 2D‐planar cylindrical geometry, immersed in a different viscous fluid and moving towards a rigid wall, is proposed for moderate Reynolds number, considering surface tension effects. The boundary integral formulation for Stokes flow inside and outside the geometry is represented in terms of a combined distribution of a single‐layer and a double‐layer potential of Green functions over the geometry surface. Additionally, non‐linear terms describing effects absent in pure Stokes flow, such as the time derivative of the velocity and inertia, are included. These effects lead to the appearance of domain integrals. Traditional dual reciprocity is applied in order to approximate these domain integrals by a series of particular solutions which are then transformed into boundary integrals. Augmented thin‐plate splines, i.e. r²log(r), plus three additional linear terms from a Pascal triangle expansion were chosen for the dual reciprocity approximation. In order to avoid the discretization of the rigid wall, and using the fact that the velocity on the wall must vanish due to the no‐slip condition, the fundamental solution was modified with a combination of image singularities including an image Stokeslet, a potential dipole and a Stokes‐doublet.

A main cause of defects within material extrusion (MatEx) additive manufacturing is the nonisothermal condition in the hot end, which causes inconsistent extrusion and polymer welding. This paper aims to validate a custom hot end design intended to heat the thermoplastic to form a melt prior to the nozzle and to reduce variability in melt temperature. A full 3D temperature verification methodology for hot ends is also presented.

Infrared (IR) thermography of steady-state extrusion for varying volumetric flow rates, hot end temperature setpoints and nozzle orifice diameters provides data for model validation. A finite-element model is used to predict the temperature of the extrudate. Model tuning demonstrates the effects of different model assumptions on the simulated melt temperature.

The experimental results show that the measured temperature and variance are functions of volumetric flow rate, temperature setpoint and the nozzle orifice diameter. Convection to the surrounding air is a primary heat transfer mechanism. The custom hot end brings the melt to its setpoint temperature prior to entering the nozzle.

This work provides a full set of steady-state IR thermography data for various parameter settings. It also provides insight into the performance of a custom hot end designed to improve the robustness of melting in MatEx. Finally, it proposes a strategy for modeling such systems that incorporates the metal components and the air around the system.

The purpose of this paper is to systematically and critically review the literature related to process design and modeling of fused deposition modeling (FDM) and similar extrusion-based additive manufacturing (AM) or rapid prototyping processes.

A systematic review of the literature focusing on process design and mathematical process modeling was carried out.

FDM and similar processes are among the most widely used rapid prototyping processes with growing application in finished part manufacturing. Key elements of the typical processes, including the material feed mechanism, liquefier and print nozzle; the build surface and environment; and approaches to part finishing are described. Approaches to estimating the motor torque and power required to achieve a desired filament feed rate are presented. Models of required heat flux, shear on the melt and pressure drop in the liquefier are reviewed. On leaving the print nozzle, die swelling and bead cooling are considered. Approaches to modeling the spread of a deposited road of material and the bonding of polymer roads to one another are also reviewed.

To date, no other systematic review of process design and modeling research related to melt extrusion AM has been published. Understanding and improving process models will be key to improving system process controls, as well as enabling the development of advanced engineering material feedstocks for FDM processes.

This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming, powder metallurgy and composite material processing are briefly discussed. The range of applications of finite elements on these subjects is extremely wide and cannot be presented in a single paper; therefore the aim of the paper is to give FE researchers/users only an encyclopaedic view of the different possibilities that exist today in the various fields mentioned above. An appendix included at the end of the paper presents a bibliography on finite element applications in material processing for 1994‐1996, where 1,370 references are listed. This bibliography is an updating of the paper written by Brannberg and Mackerle which has been published in Engineering Computations, Vol. 11 No. 5, 1994, pp. 413‐55.

Additive manufacturing (AM) is growing economically because of its cost-effective design flexibility. However, it faces challenges such as interlaminar weaknesses and reduced strength because of product anisotropy. Therefore, the purpose of this study is to develop a methodology that integrates design for additive manufacturing (AM) principles with fused filament fabrication (FFF) to address these challenges, thereby enhancing product reliability and strength.

Developed through case analysis and literature review, this methodology focuses on design methodology for AM (DFAM) principles applied to FFF for high mechanical performance applications. A DFAM database is constructed to identify common requirements and establish design rules, validated through a case study.

Existing DFAM approaches often lack failure theory integration, especially in FFF, emphasizing mechanical characterizations over predictive failure analysis in functional parts. This methodology addresses this gap by enhancing product reliability through failure prediction in high-performance FFF applications.

While some DFAM methods exist for high-performance FFF, they are often specific cases. Existing DFAM methodologies typically apply broadly across AM processes without a specific focus on failure theories in functional parts. This methodology integrates FFF with a failure theory approach to strengthen product reliability in high-performance applications.

This paper presents a boundary element method (BEM) based on a subdomain approach for the solution of non‐Newtonian fluid flow problems which include thermal effects and viscous dissipation. The volume integral arising from non‐linear terms is converted into equivalent boundary integrals by the multi‐domain dual reciprocity method (MD‐DRM) in each subdomain. Augmented thin plate splines interpolation functions are used for the approximation of field variables. The iterative numerical formulation is achieved by viewing the material as divided into small elements and on each of them the integral representation formulae for the velocity and temperature are applied and discretised using linear boundary elements. The final system of non‐linear algebraic equations is solved by a modified Newton's method. The numerical examples include non‐Newtonian problems with viscous dissipation, temperature‐dependent viscosity and natural convection due to bouyancy forces.

This paper aims to target to print functionally gradient materials (FGM) devices made of immiscible polymers in multi-material fused deposition modelling (FDM) systems. The design is intended to improve adhesion of dissimilar thermoplastics without the need for chemical compatibilization so that filaments from many different sources can be used effectively. Therefore, there is a need to invent an alternative solution for printing multiple immiscible polymers in an FDM system with the desired adhesion.

In this study, the authors have developed a bi-extruder for FDM systems which can print two thermoplastics through a single nozzle with a static intermixer to enhance bonding between input materials. The system can also change the composition of extrudates continuously.

The uniqueness of this extruder is in its easy access to the internal channel so that a static intermixer can be inserted, enabling deposition of mechanically interlocked extrudates composed of two immiscible polymers. Without this intermixer, the bi-extruder extrudes with simple side-by-side co-extrusion having no mechanical interlocking. The bi-extruder was characterized by printing objects using pairs of materials including polylactic acid, acrylonitrile butadiene styrene and high impact polystyrene. Microscope images of the cross-sections of the extrudates confirm the ability of this bi-extruder to control the composition as desired. It was also found that the mechanically interlocked extrudates composed of two immiscible polymers substantially reduces adhesion failures within and between filaments.

In this study, the first-ever FDM extruder with a mechanical blending feature next to the nozzle has been designed and used to successfully print FGM objects with improved mechanical properties.

The purpose of this paper is to review research studies on process optimisation and machine development that lead to the enhancement of final products in various aspects of the fused deposition modelling (FDM) process.

An overview of the literature, focussing on process parameters, machine developments and material characterisations. This study investigates recent research studies that studied FDM capabilities in printing a vast range of materials from thermoplastics to metal alloys.

FDM is one of the most common techniques in additive manufacturing (AM) processes. Many parameters in this technology have effects on three-dimensional printed products. Therefore, it is necessary to obtain the optimum elements, for example, build orientation, layer thickness, nozzle diameter, infill pattern and bed temperature. By selecting a proper variable range of parameters, the layers adhere strongly and building end-use products of high quality are achievable. A vast range of materials and their properties from polymers to composite-based polymers are presented. Novel techniques to print metal alloys and composites are examined to increase the productivity of the FDM process. Additionally, defects such as shrinkage and warpage are discussed to eliminate the system’s limitations and improve the quality of final products. Multi-axis and mobile machines brought enhancements throughout the process to eliminate obstacles such as staircase defects in the conventional FDM process. In brief, recent developments were identified and a summary of major improvements was discussed in this study for future research.

This paper is an overview that provides information about research and developments in FDM. This review focusses on process optimisation and obstacles in printing polymers, composites, geopolymers and novel materials. Therefore, machine characteristics were examined to find out the accessibility of printing novel materials for different applications.

The purpose of this paper is to critically review the literature related to dimensional accuracy and surface roughness for fused deposition modeling and similar extrusion-based additive manufacturing or rapid prototyping processes.

A systematic review of the literature was carried out by focusing on the relationship between process and product design parameters and the dimensional and surface properties of finished parts. Methods for evaluating these performance parameters are also reviewed.

Fused deposition modeling® and related processes are the most widely used polymer rapid prototyping processes. For many applications, resolution, dimensional accuracy and surface roughness are among the most important properties in final parts. The influence of feedstock properties and system design on dimensional accuracy and resolution is reviewed. Thermal warping and shrinkage are often major sources of dimensional error in finished parts. This phenomenon is explored along with various approaches for evaluating dimensional accuracy. Product design parameters, in particular, slice height, strongly impact surface roughness. A geometric model for surface roughness is also reviewed.

This represents the first review of extrusion AM processes focusing on dimensional accuracy and surface roughness. Understanding and improving relationships between materials, design parameters and the ultimate properties of finished parts will be key to improving extrusion AM processes and expanding their applications.

The purpose of this study was to introduce three-dimensional printing (3DP) of functionally graded sandwich foams (FGSFs). This work was continued by predicting the mechanical buckling and free vibration behavior of 3DP FGSFs using experimental and numerical analyses.

Initially, hollow glass microballoon-reinforced high-density polyethylene-based polymer composite foams were developed, and these materials were extruded into their respective filaments. These filaments are used as feedstock materials in fused filament fabrication based 3DP for the development of FGSFs. Scanning electron microscopy analysis was performed on the freeze-dried samples to observe filler sustainability. Furthermore, the density, critical buckling load (P_cr), natural frequency (f_n) and damping factor of FGSFs were evaluated. The critical buckling load (P_cr) of the FGSFs was estimated using the double-tangent method and modified Budiansky criteria.

The density of FGSFs decreased with increasing filler percentage. The mechanical buckling load increased with the filler percentage. The natural frequency corresponding to the first mode of the FGSFs exhibited a decreasing trend with an increasing load in the pre-buckling regime and an increase in post-buckled zone, whereas the damping factor exhibited the opposite trend.

The current research work is valuable for the area of 3D printing by developing the functionally graded foam based sandwich beams. Furthermore, it intended to present the buckling behavior of 3D printed FGSFs, variation of frequency and damping factor corresponding to first three modes with increase in load.