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The performance of the parts obtained by fused filament fabrication (FFF) is strongly dependent on the extent of bonding between adjacent filaments developing during the deposition stage. Bonding depends on the properties of the polymer material and is controlled by the temperature of the filaments when they come into contact, as well as by the time required for molecular diffusion. In turn, the temperature of the filaments is influenced by the set of operating conditions being used for printing. This paper aims at predicting the degree of bonding of realistic 3D printed parts, taking into consideration the various contacts arising during its fabrication, and the printing conditions selected.

A computational thermal model of filament cooling and bonding that was previously developed by the authors is extended here, to be able to predict the influence of the build orientation of 3D printed parts on bonding. The quality of a part taken as a case study is then assessed in terms of the degree of bonding, i.e. the percentage of volume exhibiting satisfactory bonding between contiguous filaments.

The complexity of the heat transfer arising from the changes in the thermal boundary conditions during deposition and cooling is well demonstrated for a case study involving a realistic 3D part. Both extrusion and build chamber temperature are major process parameters.

The results obtained can be used as practical guidance towards defining printing strategies for 3D printing using FFF. Also, the model developed could be directly applied for the selection of adequate printing conditions.

Fabrication of customized products in low volume through conventional manufacturing incurs a high cost, longer processing time and huge material waste. Hence, the concept of additive manufacturing (AM) comes into existence and fused deposition modelling (FDM), is at the forefront of researches related to polymer-based additive manufacturing. The purpose of this paper is to summarize the research works carried on the applications of FDM.

In the present paper, an extensive review has been performed related to major application areas (such as a sensor, shielding, scaffolding, drug delivery devices, microfluidic devices, rapid tooling, four-dimensional printing, automotive and aerospace, prosthetics and orthosis, fashion and architecture) where FDM has been tested. Finally, a roadmap for future research work in the FDM application has been discussed. As an example for future research scope, a case study on the usage of FDM printed ABS-carbon black composite for solvent sensing is demonstrated.

The printability of composite filament through FDM enhanced its application range. Sensors developed using FDM incurs a low cost and produces a result comparable to those conventional techniques. EMI shielding manufactured by FDM is light and non-oxidative. Biodegradable and biocompatible scaffolds of complex shapes are possible to manufacture by FDM. Further, FDM enables the fabrication of on-demand and customized prosthetics and orthosis. Tooling time and cost involved in the manufacturing of low volume customized products are reduced by FDM based rapid tooling technique. Results of the solvent sensing case study indicate that three-dimensional printed conductive polymer composites can sense different solvents. The sensors with a lower thickness (0.6 mm) exhibit better sensitivity.

This paper outlines the capabilities of FDM and provides information to the user about the different applications possible with FDM.

The hygroscopic properties of 3D-printed filaments and moisture absorption itself during the process result in dimensional inaccuracy, particularly for nozzle movement along the x-axis and for micro-scale features. In view of that, this study aims to analyze in depth the dimensional errors and deviations of the fused filament fabrication (FFF)/fused deposition modeling (FDM) 3D-printed micropillars (MPs) from the reference values. A detailed analysis into the variability in printed dimensions below 1 mm in width without any deformations in the printed shape of the designed features, for challenging filaments like polymethyl methacrylate (PMMA) has been done. The study also explores whether the printed shape retains the designed structure.

A reference model for MPs of width 800 µm and height 2,000 µm is selected to generate a g-code model after pre-processing of slicing and meshing parameters for 3D printing of micro-scale structure with defined boundaries. Three SETs, SET-A, SET-B and SET-C, for nozzle diameter of 0.2 mm, 0.25 mm and 0.3 mm, respectively, have been prepared. The SETs containing the MPs were fabricated with the spacing (S) of 2,000 µm, 3,200 µm and 4,000 µm along the print head x-axis. The MPs were measured by taking three consecutive measurements (top, bottom and middle) for the width and one for the height.

The prominent highlight of this study is the successful FFF/FDM 3D printing of thin features (<1mm) without any deformation. The mathematical analysis of the variance of the optical microscopy measurements concluded that printed dimensions for micropillar widths did not vary significantly, retaining more than 65% of the recording within the first standard deviation (SD) (±1 s). The minimum value of SD is obtained from the samples of SET-B, that is, 31.96 µm and 35.865 µm, for height and width, respectively. The %RE for SET-B samples is 5.09% for S = 2,000µm, 3.86% for S = 3,200µm and 1.09% for S = 4,000µm. The error percentage is so small that it could be easily compensated by redesigning.

The study does not cover other 3D printing techniques of additive manufacturing like stereolithography, digital light processing and material jetting.

The presented study can be potentially implemented for the rapid prototyping of microfluidics mixer, bioseparator and lab-on-chip devices, both for membrane-free bioseparation based on microfiltration, plasma extraction from whole blood, size-selection trapping of unwanted blood cells, and also for membrane-based plasma extraction that requires supporting microstructures. Our developed process may prove to be far more economical than the other existing techniques for such applications.

For the first time, this work presents a comprehensive analysis of the fabrication of micropillars using FDM/FFF 3D printing and PMMA in filament form. The primary focus of the study is to minimize the dimensional inaccuracies in the 3D printed devices containing thin features, especially in the area of biomedical engineering, by delivering benefits from the choice of the parameters. Thus, on the basis of errors and deviations, a thorough comparison of the three SETs of the fabricated micropillars has been done.

This paper aims to illustrate the integration of multiple heterogeneous sensors into a fused filament fabrication (FFF) system and the implementation of multi-sensor data fusion technologies to support the development of a “smart” machine capable of monitoring the manufacturing process and part quality as it is being built.

Starting from off-the-shelf FFF components, the paper discusses the issues related to how the machine architecture and the FFF process itself must be redesigned to accommodate heterogeneous sensors and how data from such sensors can be integrated. The usefulness of the approach is discussed through illustration of detectable, example defects.

Through aggregation of heterogeneous in-process data, a smart FFF system developed upon the architectural choices discussed in this work has the potential to recognise a number of process-related issues leading to defective parts.

Although the implementation is specific to a type of FFF hardware and type of processed material, the conclusions are of general validity for material extrusion processes of polymers.

Effective in-process sensing enables timely detection of process or part quality issues, thus allowing for early process termination or application of corrective actions, leading to significant savings for high value-added parts.

While most current literature on FFF process monitoring has focused on monitoring selected process variables, in this work a wider perspective is gained by aggregation of heterogeneous sensors, with particular focus on achieving co-localisation in space and time of the sensor data acquired within the same fabrication process. This allows for the detection of issues that no sensor alone could reliably detect.

Fabrication settings such as printing speed and nozzle temperature in fused deposition modeling undeniably influence the quality and strength of fabricated parts. As available market filaments do not contain any exact information report for printing settings, manufacturers are incapable of achieving desirable predefined print accuracy and mechanical properties for the final parts. The purpose of this study is to determine the importance of selecting suitable print parameters by understanding the intrinsic behavior of the material to achieve high-performance parts.

Two common commercial polylactic acid filaments were selected as the investigated samples. To study the specimens’ printing quality, an appropriate scaffold geometry as a delicate printing sample was printed according to a variety of speeds and nozzle temperatures, selected in the filament manufacturer’s proposed temperature range. Dimensional accuracy and qualitative surface roughness of the specimens made by one of the filaments were evaluated and the best processing parameters were selected. The scaffolds were fabricated again by both filaments according to the selected proper processing parameters. Material characterization tests were accomplished to study the reason for different filament behaviors in the printing process. Moreover, the correlations between the polymer structure, thermo-rheological behavior and printing parameters were denoted.

Compression tests revealed that precise printing of the characterized filament results in more accurate structure and subsequent improvement of the final printed sample elastic modulus.

The importance of material characterization to achieve desired properties for any purpose was emphasized. Obtained results from the rheological characterizations would help other users to benefit from the highest performance of their specific filament.

Fused deposition modelling (FDM) is the most economical additive manufacturing technique. The purpose of this paper is to describe a detailed review of this technique. Total 211 research papers published during the past 26 years, that is, from the year 1994 to 2019 are critically reviewed. Based on the literature review, research gaps are identified and the scope for future work is discussed.

Literature review in the domain of FDM is categorized into five sections – (i) process parameter optimization, (ii) environmental factors affecting the quality of printed parts, (iii) post-production finishing techniques to improve quality of parts, (iv) numerical simulation of process and (iv) recent advances in FDM. Summary of major research work in FDM is presented in tabular form.

Based on literature review, research gaps are identified and scope of future work in FDM along with roadmap is discussed.

In the present paper, literature related to chemical, electric and magnetic properties of FDM parts made up of various filament feedstock materials is not reviewed.

This is a comprehensive literature review in the domain of FDM focused on identifying the direction for future work to enhance the acceptability of FDM printed parts in industries.

This paper aims to investigate the feasibility of supportless printing of lattice structures by metal fused filament fabrication (MF³) of Ti-6Al-4V. Additionally, an empirical method was presented for the estimation of extrudate deflection in unsupported regions of lattice cells for different geometric configurations.

Metal-polymer feedstock with a solids-loading of 59 Vol.% compounded and extruded into a filament was used for three-dimensional printing of lattice structures. A unit cell was used as a starting point, which was then extended to multi-stacked lattice structures. Feasible MF³ processing conditions were identified to fabricate defect-free lattice structures. The effects of lattice geometry parameters on part deflection and relative density were investigated at the unit cell level. Computational simulations were used to predict the part quality and results were verified by experimental printing. Finally, using the identified processing and geometry parameters, multi-stacked lattice structures were successfully printed and sintered.

Lattice geometry required considerable changes in MF³ printing parameters as compared to printing bulk parts. Lattice cell dimensions showed a considerable effect on dimensional variations and relative density due to varying aspect ratios. The experimental printing of lattice showed large deflection/sagging in unsupported regions due to gravity, whereas simulation was unable to estimate such deflection. Hence, an analytical model was presented to estimate extrudate deflections and verified with experimental results. Lack of diffusion between beads was observed in the bottom facing surface of unsupported geometry of sintered unit cells as an effect of extrudate sagging in the green part stage. This study proves that MF³ can fabricate fully dense Ti-6Al-4V lattice structures that appear to be a promising candidate for applications where mechanical performance, light-weighting and design customization are required.

Supportless printing of lattice structures having tiny cross-sectional areas and unsupported geometries is highly challenging for an extrusion-based additive manufacturing (AM) process. This study investigated the AM of Ti-6Al-4V supportless lattice structures using the MF³ process for the first time.

Additive manufacturing (AM) technology has a huge influence on the real world because of its ability to manufacture massively complicated geometrics. The purpose of this study is to use CiteSpace (CS) visual analysis to identify fused deposition modeling (FDM) research and development patterns to guide researchers to decide future research and provide a framework for corporations and organizations to prepare for the development in the rapid prototyping industry. Three-dimensional printing (3DP) is defined to budget minimize manufactured input and output for aviation and the medical product industrial sectors. 3DP has implemented its potential in the Coronavirus Disease of 2019 (COVID-19) reaction.

First, 396 original publications were extracted from the web of science (WOS) with the comprehensive list and did scientometrics analysis in CS software. The parameters are specified in CS including the span (from 2011 to 2019, one year slice for the co-authorship and the co-accordance analysis), visualization (show the merged networks), specific criteria for selection (top 20%), node form (author, organization, region, reference cited; cited author, journal and keywords) and pruning (pathfinder and slicing network). Finally, correlating data was studied and showed the results of the visualization study of FDM research were shown.

The framework of FDM information is beginning to take shape. About hot research topics, there are “Morphology,” “Tensile Property by making Blends,” “Use of Carbon nanotube in 3DP” and “Topology optimization.” Regarding the latest research frontiers of FDM printing, there are “Fused Filament Fabrication,” “AM,” in FDM printing. Where “Post-processing” and “environmental impact” are the research hotspots in FDM printing. These research results can provide insight into FDM printing and useful information to consider the existing studies and developments in FDM researchers’ analysis.

Despite some important obtained results through FDM-related publications’ visualization, some deficiencies remain in this research. With >99% of articles written in English, the input data for CS was all downloaded from WOS databases, resulting in a language bias of papers in other languages and neglecting other data sources. Although, there are several challenges being faced by the FDM that limit its wide variety of applications. However, the significance of the current work concerning the technical and engineering prospects is discussed herein.

First, the novelty of this work lies in describing the FDM approach in a Scientometric way. In Scientometric investigation, leading writers, organizations, keywords, hot research and emerging knowledge points were explained. Second, this research has thoroughly and comprehensively examined the useful sustainability effects, i.e. economic sustainability, energy-based sustainability, environmental sustainability, of 3DP in industrial development in qualitative and quantitative aspects by 2025 from a global viewpoint. Third, this work also described the practical significance of FDM based on 3DP since COVID-19. 3DP has stepped up as a vital technology to support improved healthcare and other general response to emergency situations.

The limited strength of polylactic acid (PLA) hinders its extensive engineering applications. This paper aims to enhance its strength and realize diverse applications.

Here, the continuous fiber reinforced PLA composites are fabricated by a customized fused filament fabrication three-dimensional printer. Uniaxial tensile and three-point flexural tests have been conducted to analyze the reinforcement effect of the proposed composites. To unveil the adhering mechanism of optic fiber (OF) and PLA, post failure analysis including the micro imaging and morphology have been performed. The underlying mechanism is that the axial tensile strength of the OF and the interfacial adhesion between PLA and OF compete to enhance the mechanical properties of the composite.

It is found that 10%–20% enhancement of strength, ductility and toughness due to the incorporation of the continuous OF.

The continuous OFs are put into PLA first time to improve the strength. The fabrication method and process reported here are potentially applied in such engineering applications as aerospace, defense, auto, medicine, etc.

The purpose of this study is to explore the use of silver submicron-scale wire (AgSMW) additives in filament feedstock for fused filament fabrication (FFF) additive manufacturing technologies. The antibacterial effect of the additive on printed objects is assessed and its impact on mechanical behavior is determined.

AgSMW-PLA composite FFF filaments were fabricated by solution processing, granulation and extrusion. The reduction in the growth of Escherichia coli (E. coli) is measured after exposure to FFF-printed composite test specimens with AgSMW additive concentrations ranging from 0.0 to 10.0 weight per cent. The effect of the additive addition on the thermal properties and tensile mechanical performance was measured. Scanning electron microscopy (SEM) was used to analyze the composite microstructure and fracture behavior.

E. coli growth was reduced by approximately 50 per cent at the highest additive concentration of 10.0 weight per cent. This is attributed to the release of silver ions through water diffusion into the bulk of the composite. The ultimate tensile strength declined with increasing AgSMW concentration with a moderate reduction of 18 per cent at 10.0 weight per cent. The elastic modulus did not vary significantly at any of the concentrations studied. The ductility of the composite was only notably reduced at the highest concentration. The reduction in mechanical strength and strain at break is attributed to an increase in void defects in the composite with increasing additive concentration.

This study demonstrates the successful incorporation of AgSMWs into FFF-compatible filaments for use in commercially available printing systems. The results demonstrate significant reduction of bacteria growth when using these materials. While the mechanical performance degrades slightly, the results indicate the material’s efficacy for a variety of potential biomedical applications. As a proof of concept, surgical tools were printed using the composite.