Material Extrusion Research Articles

Effect of Four Process Parameters on Flexural Strength and Porosity of Metakaolin Ceramics Fabricated by Material Extrusion: Optimization and Predictive Models via Orthogonal Experiments

A high‐strength metakaolin‐based porous ceramics are fabricated using slurry‐based material extrusion via optimizing four key process parameters, including nozzle internal diameter, height to diameter ratio, filling rate, and printing speed. The orthogonal experiments are used to adjust flexural strength and porosity, and the optimal process parameters are obtained by comprehensive scoring and range analysis methods. The predictive models of strength‐parameters, porosity‐parameters, and strength‐porosity are established and validated. The results show that the optimal process parameters for high‐strength and high‐porosity ceramics are 0.51 mm nozzle internal diameter, 70% height to diameter ratio, 100% filling rate, and 15 mm s−1 printing speed. The correctness and predictability of three predictive models are proved by two methods, which are the mutual validation and comparison between theoretical and actual values. And the error rates between theoretical and actual results are less than 7%. This work provides guidance for the rapid fabrication of ceramics with adjustable strength and porosity by material extrusion, and the established predictive models can pave the way for its wider application in the practice.

In-process evaluation of layer defects and surface topography on material extruded parts through a novel point cloud functional analysis

Abstract Material extrusion (MEX) is one of the most used additive manufacturing technologies, thanks to its appealing in various industrial fields. Despite its numerous advantages, process quality remains an issue when compared to other, more established technologies. In-process monitoring has become fundamental to meet the tight requirements of precision industries. In this work, a novel MEX monitoring methodology based on point-cloud functional analysis was tested and discussed. Using a blue-laser line profilometer integrated into a consumer 3D printer, the point cloud of each layer was obtained immediately after its completion and subsequently analysed. Functional analysis tools were employed to characterize the surface topography and assess the distribution of material and voids to detect defects. Common defective conditions in the form of excess or lack of deposited material, referred to as overfill and underfill, respectively, were induced by varying printing parameters and the specimen’s cross-section. After slicing the layer surface according to specified height thresholds, functional parameters such as the projected percentage area (PPA), void and material volume percentage and void and material mean thickness were computed and analysed. Results indicated that the PPA values effectively depicted the overall surface conditions and served as a suitable initial step for enabling corrective actions through the contour extraction of defective regions. Meanwhile, the percentage volume and mean thickness of voids and material, referred to as functional parameters, provided more detailed insights into the morphology of the layer surface and the detected defects.

Mechanical Behavior of 3D-Printed Zig-Zag Honeycomb Structures Made of BASF Ultrafuse 316L

The aim of this study is to determine the mechanical behavior of 2D honeycomb cellular structures with deformation initiators subject to quasi-static compression testing. Two different loading directions were studied: in-plane (IP) and out-of-plane (OP). The deformation initiators sought to stabilize the mechanical response by decreasing the initial peak force in the case of OP loading. The samples for testing were made using stainless steel 316L that was 3D-printed using material extrusion (MEX). The method enables fabrication of structures with high mechanical strength and ductility. The findings of the quasi-static compression testing showed that the additional deformation initiators were able to significantly reduce the orthotropy in the mechanical response of honeycomb cellular structures.

On secondary recycling of high-density polyethylene with reinforcement of stubble powder by a material extrusion process for construction applications

In the past two decades, several studies have been reported using agricultural waste as reinforcement in thermoplastic matrices for lightweight and tunable mechanical properties. However, the recycling of thermoplastic with reinforcement of agricultural waste has constraints in the form of the volume of recycled material to support the concept of a circular economy. One of the solutions for bulk consumption of such agricultural and thermoplastic waste is its use in construction applications. In the present study, high-density polyethylene (HDPE) was secondary (2°) recycled by reinforcement of stubble waste powder (SWP) through the material extrusion (MEX) process for possible applications in the construction industry. The melt flow index (MFI) investigation suggested the maximum loading of 15% SWP with the recycled HDPE matrix in the present case study. Further, the filament was prepared by using the design of experiment (DoE) with input parameters (heat treatment (pre-heat treatment (PreHT) and post-heat treatment (PostHT), barrel temperature (170–180°C) and screw speed (3–5 RPM) on single screw extruder). The results suggest that the combination of PreHT, 170°C-barrel temperature and 4 RPM screws speed resulted in a maximum Young’s modulus (E) of 1386.57 MPa. The PreHT has promoted the recrystallization of the HDPE-SWP blend, which has significantly increased E. The differential scanning calorimetry (DSC) reveals that the HDPE-SWP composite was more thermally stable after each thermal cycle. In addition, the results of this study were also supported and correlated with the observation of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), surface profiling and 3D printability with MEX.

Green Recycling for Polypropylene Components by Material Extrusion

High volumetric shrinkage and rheological behavior of polypropylene (PP) are the main problems that make material extrusion (MEX) uncommon for this material. The complexity is raised when recycled materials are used. This research covered different aspects of the MEX process of virgin and recycled PP, from the analysis of rough materials to the mechanical evaluation of the final products. Two types of virgin PP (one in pellet and the other in filament form) and one recycled PP were analyzed. Thermal characterization and rheological analysis of these materials were initially employed to understand the peculiar properties of all investigated PP and set filament extrusion. The 3D parts were then printed using processed filaments to check fabrication quality through visual analysis and mechanical tests. A well-structured approach was proposed to encompass the limitations of PP 3D printing by accurately evaluating the influence of the material properties on the final part performance. The results revealed that the dimensional and mechanical performances of the recycled PP were comparable with the virgin filament commonly employed in MEX, making it particularly suitable for this application.

Correction: New pressure model for a typical extruder nozzle in material extrusion additive manufacturing

Correction: New pressure model for a typical extruder nozzle in material extrusion additive manufacturing

Optimizing bonding conditions between multilayer FFF material extrusion

ABSTRACT Multi−material 3D printing using the material extrusion (ME) process is paramount for functionally graded parts. Finding the optimum parameters of the customized multi−material part is an issue in the filament ME field. Environmentally friendly materials, such as polylactic acid (PLA) or composites of PLA/wood (PLAW), can be 3D-printed under similar conditions to PLA. This work’s main objective is optimizing the printing speed and temperature of multi−materials in sandwich form using PLAW as a core between two PLA sheets in 3D-printing bending parts. To this extent, nine 3D-printings were performed under different printing conditions on PLA, PLAW, and PLA/PLAW/PLA, showing that the PLA/PLAW/PLA has an average bending strength similar to PLA (71.05 vs. 88.5 MPa) and four times higher than the PLAW (71.5 vs. 17.34 MPa). The 210°C and 45 mm/s printing temperature and speed optimize the bonding quality of all parts. This work will be valuable for digitally designed multi-layer parts.

Development of Thermosensitive Hydrogels with Tailor-Made Geometries to Modulate Cell Harvesting of Non-Flat Cell Cultures

Considering the complexity in terms of design that characterizes the different tissues of the human body, it is necessary to study and develop more precise therapies. In this sense, this article presents the possibility of fabricating photocurable thermosensitive hydrogels with free geometry and based on N-Vinyl Caprolactam (VCL) with the aim of modulating the adhesion of non-planar cell cultures. The fabrication process is based on the use as a mold of two-layer thick water-soluble polyvinyl alcohol (PVA) previously printed by Extrusion Material (MatEx). From this technology it has been possible to obtain hydrogels with different 3D geometries and different crosslinking percentages (2, 4 and 6 mol%). Studies have shown that networks reduce their thermosensitivity not only when the percentage of crosslinking in the formulation increases, but also when the thickness of the hydrogel obtained increases. Based on this reduction in thermosensitivity, the less crosslinked (2 mol%) hydrogels have been evaluated to carry out a novel direct application in which hydrogels with curved geometry have allowed cell adhesion and proliferation at 37 °C with the endothelial cell line C166-GFP; likewise, non-aggressive cell detachment was observed when the hydrogel temperature was reduced to values of 20 °C. Therefore, the present manuscript shows a novel application for the synthesis of free-form thermosensitive hydrogels that allows modulation of non-planar cell cultures.

Predictive modelling of flexural behaviour of polymer composites: a machine learning approach through material extrusion

Predictive modelling of flexural behaviour of polymer composites: a machine learning approach through material extrusion

Bio‐Inspired Graded and Uniform Cylindrical Lattices Fabricated by Material Extrusion 3D Printing: An Experimental and Numerical Investigation

ABSTRACTThe main requirements of the biomedical and aerospace industries are new and innovative lightweight materials. Bio‐inspired structures, which are inspired by various biological designs, have demonstrated notable advancements over traditional lightweight structures. In this study, bioinspired uniform and graded cylindrical triply periodic minimal surface (TPMS) and strut‐based lattice structures were studied for their mechanical qualities and energy absorption capacities fabricated by material extrusion 3D printing using PLA material. It was found that the cylindrical TPMS diamond lattice achieved maximum stress of 78.5 MPa and absorbed 19.14 MJ/m3 of energy, outperforming strut‐based designs with a 48% higher energy absorption than cylindrical BCC lattice structure. Graded designs further improve energy absorption through a better stress distribution. The findings validated the Gibson–Ashby model, highlighting the enhanced load distribution and stress transfer in the strut‐based and TPMS diamond structures. The finite element (FE) model results closely matched the experimental data, confirming its predictive reliability with a maximum error of energy absorption of 7.7%, elastic modulus of 6.9%, and plateau stress of 4.7%. These insights underscore the superior energy absorption and mechanical stability of cylindrical TPMS diamond lattices, indicating their potential for satisfying stringent industrial and technical performance requirements. The novelty of these designs lies in their bioinspired structures and significant enhancements in mechanical performance and energy absorption. Future research should build on these results to design efficient materials tailored to specific needs using FE models to optimize development processes before experimental testing.

Tailoring the Mechanical Properties of Fungal Mycelium Mats with Material Extrusion Additive Manufacturing of PHBH and PLA Biopolymers

Tailoring the Mechanical Properties of Fungal Mycelium Mats with Material Extrusion Additive Manufacturing of PHBH and PLA Biopolymers

On the Hydrodynamic and Structural Performance of Thermoplastic Composite Ship Propellers Produced by Additive Manufacturing Method

In the marine industry, the search for sustainable methods, materials, and processes, from the product’s design to its end-of-life stages, is a necessity for combating the negative consequences of climate change. In this context, the lightening of products is essential in reducing their environmental impact throughout their life. In addition to lightening through design, lightweight materials, especially plastic-based composites, will need to be used in new and creative ways. The material extrusion technique, one of the additive manufacturing methods, is becoming more widespread day by day, especially in the production of objects with complex forms. This prevalence has not yet been reflected in the marine industry. In this study, the performances of plastic composite propellers produced by the material extrusion technique is investigated and discussed comparatively with the help of both hydrodynamic and structural tests carried out in a cavitation tunnel and mechanical laboratory. The cavitation tunnel test and numerical simulations were conducted at a range of advance coefficients (J) from 0.3 to 0.9. The shaft rate was kept at 16 rps. The thrust and torque data were obtained using the tunnel dynamometer. Digital pictures were taken to obtain structural deformation and cavitation dynamics. The structural performance of the propellers shows that an aluminum propeller is the most rigid, while a short carbon fiber composite propeller is the most flexible. Continuous carbon fiber composite has high strength and stiffness, while continuous glass fiber composite is more cost-effective. In terms of the hydrodynamic performance of the propellers, flexibility reduces the loading on the blade, which can result in thrust and torque reduction. Overall, the efficiency of the composite propellers was similar and less than that of the rigid aluminum propeller. In terms of weight, the composite carbon propeller containing continuous fiber, which is half the weight of the metal propeller, is considered as an alternative to metal in production. These propellers were produced from a unique composite consisting of polyamide, one of the thermoplastics that is a sustainable composite material,, and glass and carbon fiber as reinforcements. The findings showed that the manufacturing method and the new composites can be highly successful for producing ship components.

Tailoring thermal conductivity and printability in boron nitride/epoxy nano- and micro-composites for material extrusion 3D printing

This study explores the design and characterization of boron nitride (BN)/epoxy nano- and micro-composites, utilizing material extrusion 3D printing as a powerful technique to align filler particles within the matrix and produce effective thermally conductive and electrically insulating adhesive materials with possible applications in electronics. Investigating the uncharted correlation between filler morphology, including both boron nitride microplatelets (BNMP) and boron nitride nanosheets (BNNS), processability by additive manufacturing (AM), and ink functionalities, BNMP proves more effective in boosting thermal conductivity, with an enhancement of up to 400%. Fillers, that can be highly oriented through material extrusion, contribute to achieving high glass transition temperature (up to 137 °C) and thermal resistance, expanding the inks’ applicability. Optimized inks demonstrate exceptional shape fidelity, enabling the fabrication of complex structures. The findings emphasize the crucial role of ceramic filler content and morphology in optimizing multifunctional 3D-printed materials' performance and tailoring their properties, offering insights for future innovations in electronic materials and manufacturing methodologies for thermal management applications.

A green inorganic binder for material extrusion of ultra-low shrinkage and relatively high strength metakaolin ceramics at low sintering temperature

Ultra-low shrinkage and relatively high strength metakaolin ceramics printed by material extrusion were innovatively fabricated using inorganic aluminum dihydrogen phosphate (Al(H2PO4)3) as a binder and low sintering temperature. The optical microscopy, scanning electron microscopy (SEM), electronic vernier caliper, three-point bending test, Archimedes method and X-ray diffraction (XRD) were used to measure and evaluate the surface morphology, microstructure, dimensional shrinkage, flexural strength, porosity and phase composition of the printed ceramics sintered at different temperatures. The results showed that when the mass ratio of metakaolin, Al(H2PO4)3 and deionized water was 17:6:2, the rheological characteristic of the purely green inorganic ceramic slurry was very suitable for material extrusion additive manufacturing, and the corresponding printed ceramic green bodies possessed high-quality formability. The ceramic samples sintered at 750 °C possessed the best whiteness, the lowest shrinkage (<2%), relatively high flexural strength (9.02 MPa). As the sintering temperature increased, Al(H2PO4)3 transformed to aluminum metaphosphate Al(PO3)3, and then decomposed into aluminum phosphate (AlPO4) and phosphorus pentoxide gas (P2O5), which caused pores and reduced strength, and alumina oxide (Al2O3) and silicon oxide (SiO2) in metakaolin gradually transformed to mullite and cristobalite with more stable structure and higher strength.

Material extrusion additive manufacturing of recycled discontinuous carbon fibre reinforced thermoplastic composites with high fibre efficiency

The study proposes a novel method, named angled feeding extrusion (AFE), for material extrusion additive manufacturing (MEX AM) of discontinuous recycled carbon fibre (rCF) reinforced thermoplastic composites with high fibre efficiency. The AFE system is also integrated with a 5-axis printer to enable the fabrication of complex structures. Characterisation of fibre morphology and structure is conducted using X-ray computed microtomography (μCT), and the mechanical properties of the AFE-manufactured rCF composites are investigated through mechanical testing. The results show that AFE demonstrates effectiveness in reducing the fabrication difficulty of rCF composites with high fibre efficiency, fibre efficiency encompasses factors such as fibre fraction, length, and orientation. Moreover, rCF composites additively manufactured by the AFE system achieve rCF lengths of up to 3.8mm and a fibre volume fraction of 30.3%. The tensile strength and modulus are 178MPa and 9.9GPa respectively. It exhibits a significant improvement of 90% and 254% in tensile strength and modulus compared to short fibre reinforced composites. Similarly, compressive tests of AFE-manufactured composite rings show an increase of 80% in ultimate compressive load.

Effect of shear-thinning rheology on the dynamics and pressure distribution of a single rigid ellipsoidal particle in viscous fluid flow

This paper evaluates the behavior of a single rigid ellipsoidal particle suspended in homogeneous viscous flow with a power-law generalized Newtonian fluid rheology using a custom-built finite element analysis (FEA) simulation. The combined effects of the shear-thinning fluid rheology, the particle aspect ratio, the initial particle orientation, and the shear-extensional rate factor in various homogeneous flow regimes on the particles dynamics and surface pressure evolution are investigated. The shear-thinning fluid behavior was found to modify the particle's trajectory and alter the particle's kinematic response. Moreover, the pressure distribution over the particle's surface is significantly reduced by the shear-thinning fluid rheology. The FEA model is validated by comparing results of the Newtonian case with results obtained from the well-known Jeffery's analytical model. Furthermore, Jeffery's model is extended to define the particle's trajectory in a special class of homogeneous Newtonian flows with combined extension and shear rate components typically found in axisymmetric nozzle flow contractions. The findings provide an improved understanding of key transport phenomenon related to physical processes involving fluid–structure interaction such as that which occurs within the flow field developed during material extrusion–deposition additive manufacturing of fiber-reinforced polymeric composites. These results provide insight into important microstructural formations within the print beads.

Comprehensive study of PLA material extrusion 3D printing optimization and its comparison with PLA injection molding through life cycle assessment

Comprehensive study of PLA material extrusion 3D printing optimization and its comparison with PLA injection molding through life cycle assessment

Application of Image Recognition Technology in Nozzle Cleaning for Material Extrusion Additive Manufacturing Processes

Application of Image Recognition Technology in Nozzle Cleaning for Material Extrusion Additive Manufacturing Processes

Modeling the effects of thermal contact resistance on mechanical properties in material extrusion additive manufacturing

Modeling the effects of thermal contact resistance on mechanical properties in material extrusion additive manufacturing

Modified CEL method for determination of defect formation mechanism in underwater stationary shoulder FSW based on softened pressure-overclosure contact relationship

The Coupled Eulerian-Lagrangian (CEL) method was employed to simulate underwater friction stir welding with a stationary shoulder tool (USSFSW). The governing equations in the CEL method were formulated for FSW based on the immersed boundary method. A new softened pressure-overclosure model was introduced to define contact pressure within the overclosure zone, and an initial nodal clearance control method was implemented to prevent the penetration of Eulerian elements into the Lagrangian domain. For modeling the mechanical and thermal interactions between surfaces, the VUINTERACTION subroutine was utilized. The study focused on the defect formation mechanisms during USSFSW, highlighting the roles of material flow velocity and nodal forces. Simulation results demonstrated close alignment with experimental data, revealing three flow paths that developed during the process, merging in the empty area behind the pin and generating upward material flow. Notably, the maximum flow velocity at the boundary of the third and fourth quadrants ranged from 0.189 to 0.495 m/s, while the overall maximum material flow velocity varied from 0.193 to 0.502 m/s. The nodal force was found to vary between 180 and 600 N; notably, when this force dropped below 200 N, the driving force for material flow decreased, resulting in the inability to fill the cavity behind the tool. Conversely, increasing the nodal force enhanced both backward flow (BF) and horizontal flow (HF), promoting higher material extrusion into the cavity. ​Ultimately, when the flow velocity fell below approximately 0.25 mm/s and the nodal force dropped below about 200 N, cavity defects in USSFSW became inevitable.