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19 pages, 16807 KiB

Open AccessEditor’s ChoiceArticle

Using 3D Density-Gradient Vectors in Evolutionary Topology Optimization to Find the Build Direction for Additive Manufacturing

by Dylan Bender and Ahmad Barari

J. Manuf. Mater. Process. 2023, 7(1), 46; https://doi.org/10.3390/jmmp7010046 - 09 Feb 2023

Cited by 1 | Viewed by 1689

Abstract

Given its layer-based nature, additive manufacturing is known as a family of highly capable processes for fabricating complex 3D geometries designed by means of evolutionary topology optimization. However, the required support structures for the overhanging features of these complex geometries can be concerningly [...] Read more.

Given its layer-based nature, additive manufacturing is known as a family of highly capable processes for fabricating complex 3D geometries designed by means of evolutionary topology optimization. However, the required support structures for the overhanging features of these complex geometries can be concerningly wasteful. This article presents an approach for studying the manufacturability of the topology-optimized complex 3D parts required for additive manufacturing and finding the optimum corresponding build direction for the fabrication process. The developed methodology uses the density gradient of the design matrix created during the evolutionary topology optimization of the 3D domains to determine the optimal build orientation for additive manufacturing with the objective of minimizing the need for support structures. Highly satisfactory results are obtained by implementing the developed methodology in analytical and experimental studies, which demonstrate potential additive manufacturing mass savings of 170% of the structure’s weight. The developed methodology can be readily used in a variety of evolutionary topology optimization algorithms to design complex 3D geometries for additive manufacturing technologies with a minimized level of waste due to reducing the need for support structures. Full article

(This article belongs to the Special Issue Recent Advances in Processes and Design Methods for Additive Manufacturing)

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23 pages, 8556 KiB

Open AccessArticle

Influence of Ambient Temperature and Crystalline Structure on Fracture Toughness and Production of Thermoplastic by Enclosure FDM 3D Printer

by Supaphorn Thumsorn, Wattanachai Prasong, Akira Ishigami, Takashi Kurose, Yutaka Kobayashi and Hiroshi Ito

J. Manuf. Mater. Process. 2023, 7(1), 44; https://doi.org/10.3390/jmmp7010044 - 08 Feb 2023

Cited by 7 | Viewed by 2427

Abstract

Fused deposition modeling (FDM) 3D printing has printed thermoplastic materials layer-by-layer to form three dimensional products whereby interlayer adhesion must be well controlled to obtain high mechanical performance and product integrity. This research studied the effects of ambient temperatures and crystalline structure on [...] Read more.

Fused deposition modeling (FDM) 3D printing has printed thermoplastic materials layer-by-layer to form three dimensional products whereby interlayer adhesion must be well controlled to obtain high mechanical performance and product integrity. This research studied the effects of ambient temperatures and crystalline structure on the interlayer adhesion and properties of thermoplastic FDM 3D printing. Five kinds of poly(lactic acid) (PLA) filaments, both commercially available and the laboratory-made, were printed using the enclosure FDM 3D printer. The ambient temperatures were set by the temperature-controlled chamber from room temperature to 75 °C with and without a cooling fan. The interlayer adhesion was characterized by the degree of entanglement density, morphology, and fracture toughness. In addition, PLA filament with high crystallinity has induced heat resistance, which could prevent filament clogging and successfully print at higher chamber temperatures. The ambient temperature increased with increased chamber temperature and significantly increased when printed without a cooling fan, resulting in improved interlayer bonding. The crystalline structure and dynamic mechanical properties of the 3D printed products were promoted when the chamber temperature was increased without a cooling fan, especially in PLA composites and PLA containing a high content of L-isomer. However, although the additives in the PLA composite improved crystallinity and the degree of entanglement density in the 3D-printed products, they induced an anisotropic characteristic that resulted in the declination of the interlayer bonding in the transverse orientation products. The increasing of chamber temperatures over 40 °C improved the interlayer bonding in pristine PLA products, which was informed by the increased fracture toughness. Further, it can be noted that the amorphous nature of PLA promotes molecular entanglement, especially when printed at higher chamber temperatures with and without a cooling fan. Full article

(This article belongs to the Special Issue Recent Advances in Processes and Design Methods for Additive Manufacturing)

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14 pages, 8134 KiB

Open AccessArticle

Investigation of the Pull-Out Behaviour of Metal Threaded Inserts in Thermoplastic Fused-Layer Modelling (FLM) Components

by Tobias Kastner, Juliane Troschitz, Christian Vogel, Thomas Behnisch, Maik Gude and Niels Modler

J. Manuf. Mater. Process. 2023, 7(1), 42; https://doi.org/10.3390/jmmp7010042 - 07 Feb 2023

Cited by 1 | Viewed by 1760

Abstract

To provide detachable, secure and long-term stable joints in fused-layer modelling (FLM) components or assemblies, metal threaded inserts are widely used as extrinsic interfaces. However, the load-bearing capacity of such inserts is influenced by the inhomogeneous, anisotropic material structure of the FLM components. [...] Read more.

To provide detachable, secure and long-term stable joints in fused-layer modelling (FLM) components or assemblies, metal threaded inserts are widely used as extrinsic interfaces. However, the load-bearing capacity of such inserts is influenced by the inhomogeneous, anisotropic material structure of the FLM components. This work evaluates the influence of the joining zone design and the printing process parameters on the achievable joint properties. Therefore, we printed thermoplastic FLM test specimens with varying parameters for infill density, wall thickness, layer height and nozzle temperature. Subsequently, metal threaded inserts were warm-embedded into the test specimens and investigated in quasi-static pull-out tests. The results show that the infill density in the joining zone has the largest impact on the joint strength and should be 70% or higher. Furthermore, an analysis of different wall thicknesses around the pre hole shows that a minimum value of

2.4

mm is required for the selected insert geometry to achieve a high pull-out force. Increasing the wall thickness beyond this value does not significantly affect the joint strength. The results provide an improved base for detailed understanding and interface design in FLM components for the integration of metal threaded inserts as well as for further investigations regarding different printing materials and load types. Full article

(This article belongs to the Special Issue Recent Advances in Processes and Design Methods for Additive Manufacturing)

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23 pages, 86090 KiB

Open AccessArticle

Load Introduction Specimen Design for the Mechanical Characterisation of Lattice Structures under Tensile Loading

by Justin Jung, Guillaume Meyer, Matthias Greiner and Christian Mittelstedt

J. Manuf. Mater. Process. 2023, 7(1), 37; https://doi.org/10.3390/jmmp7010037 - 01 Feb 2023

Cited by 2 | Viewed by 2053

Abstract

In recent years, it has been demonstrated that the lightweight potential of load-carrying structural components could be further enhanced using additive manufacturing technology. However, the additive manufacturing process offers a large parameter space that highly impacts the part quality and their inherent mechanical [...] Read more.

In recent years, it has been demonstrated that the lightweight potential of load-carrying structural components could be further enhanced using additive manufacturing technology. However, the additive manufacturing process offers a large parameter space that highly impacts the part quality and their inherent mechanical properties. Therefore, the most influential parameters need to be identified separately, categorised, classified and incorporated into the design process. To achieve this, the reliable testing of mechanical properties is crucial. The current developments concerning additively manufactured lattice structures lack unified standards for tensile testing and specimen design. A key factor is the high stress concentrations at the transition between the lattice structure and the solid tensile specimen’s clamping region. The present work aims to design a topology-optimised transition region applicable to all cubic unit cell types that avoids high samples potentially involved in structural grading. On the basis of fulfilling the defined objective and satisfying the constraints of the stress and uniaxiality conditions, the most influential parameters are identified through a correlation analysis. The selected design solutions are further analysed and compared to generic transition design approaches. The most promising design features (compliant edges, rounded cross-section, pillar connection) are then interpreted into structural elements, leading to an innovative generic design of the load introduction region that yields promising results after a proof-of-concept study. Full article

(This article belongs to the Special Issue Recent Advances in Processes and Design Methods for Additive Manufacturing)

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19 pages, 7479 KiB

Open AccessArticle

Extrusion Additive Manufacturing of PEI Pellets

by Matteo Fabrizio, Matteo Strano, Daniele Farioli and Hermes Giberti

J. Manuf. Mater. Process. 2022, 6(6), 157; https://doi.org/10.3390/jmmp6060157 - 08 Dec 2022

Cited by 4 | Viewed by 2001

Abstract

The simplest, most cost-efficient, and most widespread Additive Manufacturing (AM) technology is Extrusion Additive Manufacturing (EAM). Usually, EAM is performed with filament feedstock, but using pellets instead of filaments yields many benefits, including significantly lower cost and a wider choice of materials. High-performance [...] Read more.

The simplest, most cost-efficient, and most widespread Additive Manufacturing (AM) technology is Extrusion Additive Manufacturing (EAM). Usually, EAM is performed with filament feedstock, but using pellets instead of filaments yields many benefits, including significantly lower cost and a wider choice of materials. High-performance polymers offer high strength even when produced with AM technique, allowing to produce near-net-shape functional parts. The production of these materials in filament form is still limited and expensive; therefore, in this paper, the possibility of producing AM components with engineering polymers from pellets will be thoroughly investigated. In this work, the effectiveness of a specially designed AM machine for printing high-performance materials in pellet form was tested. The material chosen for the investigation is PEI 1000 which offers outstanding mechanical and thermal properties, giving the possibility to produce with EAM functional components. Sensitivity analyses have been carried out to define a process window in terms of thermal process parameters by observing different response variables. Using the process parameters in the specified range, the additive manufactured material has been mechanically tested, and its microstructure has been investigated, both in dried and undried conditions. Finally, a rapid tool for sheet metal forming has been produced. Full article

(This article belongs to the Special Issue Recent Advances in Processes and Design Methods for Additive Manufacturing)

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24 pages, 19128 KiB

Open AccessArticle

Towards an Ideal Energy Absorber: Relating Failure Mechanisms and Energy Absorption Metrics in Additively Manufactured AlSi10Mg Cellular Structures under Quasistatic Compression

by Mandar Shinde, Irving E. Ramirez-Chavez, Daniel Anderson, Jason Fait, Mark Jarrett and Dhruv Bhate

J. Manuf. Mater. Process. 2022, 6(6), 140; https://doi.org/10.3390/jmmp6060140 - 13 Nov 2022

Cited by 4 | Viewed by 2199

Abstract

A designer of metallic energy absorption structures using additively manufactured cellular materials must address the question of which of a multitude of cell shapes to select from, the majority of which are classified as either honeycomb, beam-lattice, or Triply Periodic Minimal Surface (TPMS) [...] Read more.

A designer of metallic energy absorption structures using additively manufactured cellular materials must address the question of which of a multitude of cell shapes to select from, the majority of which are classified as either honeycomb, beam-lattice, or Triply Periodic Minimal Surface (TPMS) structures. Furthermore, there is more than one criterion that needs to be assessed to make this selection. In this work, six cellular structures (hexagonal honeycomb, auxetic and Voronoi lattice, and diamond, gyroid, and Schwarz-P TPMS) spanning all three types were studied under quasistatic compression and compared to each other in the context of the energy absorption metrics of most relevance to a designer. These shapes were also separately studied with tubes enclosing them. All of the structures were fabricated out of AlSi10Mg with the laser powder bed fusion (PBF-LB. or LPBF) process. Experimental results were assessed in the context of four criteria: the relationship between the specific energy absorption (SEA) and maximum transmitted stress, the undulation of the stress plateau, the densification efficiency, and the design tunability of the shapes tested—the latter two are proposed here for the first time. Failure mechanisms were studied in depth to relate them to the observed mechanical response. The results reveal that auxetic and Voronoi lattice structures have low SEA relative to maximum transmitted stresses, and low densification efficiencies, but are highly tunable. TPMS structures on the other hand, in particular the diamond and gyroid shapes, had the best overall performance, with the honeycomb structures between the two groups. Enclosing cellular structures in tubes increased peak stress while also increasing plateau stress undulations. Full article

(This article belongs to the Special Issue Recent Advances in Processes and Design Methods for Additive Manufacturing)

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11 pages, 3867 KiB

Open AccessArticle

Permeability of Additive Manufactured Cellular Structures—A Parametric Study on 17-4 PH Steels, Inconel 718, and Ti-6Al-4V Alloys

by Ting-Wei Liu, Tien-Lin Cheng, Kuo-Chi Chiu and Jhewn-Kuang Chen

J. Manuf. Mater. Process. 2022, 6(5), 114; https://doi.org/10.3390/jmmp6050114 - 01 Oct 2022

Viewed by 2000

Abstract

Cellular structures of metallic alloys are often made for various industrial applications by additive manufacturing. The permeability for fluid flow in these cellular structures is important. The current investigated the gas fluidity of cellular structures made by selective laser melting (SLM). The porosity [...] Read more.

Cellular structures of metallic alloys are often made for various industrial applications by additive manufacturing. The permeability for fluid flow in these cellular structures is important. The current investigated the gas fluidity of cellular structures made by selective laser melting (SLM). The porosity and permeability of the SLM cellular structures were measured for 17-4 PH stainless steel, Inconel 718, and Ti-6Al-4V alloys. The relations between porosity and energy density are expressed using the power law. The characteristic molar energies were 1.07 × 10⁵, 9.02 × 10⁴, and 7.11 × 10⁴ J/mole for 17-4 PH steel, Ti-6Al-4V, and Inconel 718 alloys, respectively. 17-4 PH steel gave rise to higher porosity at the same energy density when compared with Ti-6Al-4V and Inconel 718 alloy. The values of these molar energy density are related to the heat needed to melt the alloys, viscosity, and thermal conductivity. It was further shown that air permeability is not only concerned with the percentage of porosity in the cellular materials, but it also relates to the tortuosity of pore pathways formed in the cellular materials. At the same porosity, Inconel 718 demonstrates higher air permeability in comparison with that of Ti-6Al-4V and 17-4 PH alloys due to its smoother pore pathways. Ti-6Al-4V, on the other hand, demonstrates the highest specific surface areas due to powder sticking along the pore pathways and led to the lowest permeability among the three alloys. Full article

(This article belongs to the Special Issue Recent Advances in Processes and Design Methods for Additive Manufacturing)

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25 pages, 3270 KiB

Open AccessArticle

Study of SLA Printing Parameters Affecting the Dimensional Accuracy of the Pattern and Casting in Rapid Investment Casting

by Nazym Badanova, Asma Perveen and Didier Talamona

J. Manuf. Mater. Process. 2022, 6(5), 109; https://doi.org/10.3390/jmmp6050109 - 28 Sep 2022

Cited by 20 | Viewed by 3360

Abstract

Dimensional accuracy and geometric characteristics of the manufactured parts bear significant importance in product assembly. In Rapid Investment Casting, these characteristics can be affected by the printing parameters of the Additive Manufacturing method used in the pattern production process. Stereolithography is one of [...] Read more.

Dimensional accuracy and geometric characteristics of the manufactured parts bear significant importance in product assembly. In Rapid Investment Casting, these characteristics can be affected by the printing parameters of the Additive Manufacturing method used in the pattern production process. Stereolithography is one of the important AM techniques mostly exploited in RIC due to its accuracy, smooth surface, and precision. However, the effect of SLA printing parameters on the dimensional accuracy and geometric characteristics have not been studied thoroughly. This study considers an experimental approach to study the effect of SLA printing parameters such as layer thickness, build angle, support structure density, and support touchpoint size on the dimensional accuracy and geometrical characteristics of the Castable Wax printed patterns and the Al cast parts. Taguchi’s Design of Experiment was used to define the number of experimental runs. SolidCast simulation was used to design the orientation of casting feeder to achieve directional solidification. Coordinate Measuring Machine measurements of deviations in the printed and cast parts were analyzed using the “Smaller-the-better” scheme in the two-step optimization method of Taguchi experiments. Build angle and Layer thickness were identified to be the first and the second most impactful parameters, respectively, affecting both the dimensional and geometric accuracy of Castable Wax patterns and Al cast parts, with optimal values of 0 deg and 0.25 μm, respectively. Both printed and cast parts had twice as many deviations in geometry as in dimensions. The sphere roundness and angularity were found to be the most and least accurate geometric characteristics, respectively. The dimensions in the Z direction were more accurate than in the X-Y directions, showing the smallest size deviations for height measurements and large deviations in the length, width, and diameter of the hole. Full article

(This article belongs to the Special Issue Recent Advances in Processes and Design Methods for Additive Manufacturing)

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13 pages, 7275 KiB

Open AccessArticle

A Combination of Alloy Modification and Heat Treatment Strategies toward Enhancing the Properties of LPBF Processed Hot Working Tool Steels (HWTS)

by Iris Raffeis, Frank Adjei-Kyeremeh, Simon Ewald, Johannes Henrich Schleifenbaum and Andreas Bührig-Polaczek

J. Manuf. Mater. Process. 2022, 6(3), 63; https://doi.org/10.3390/jmmp6030063 - 10 Jun 2022

Cited by 4 | Viewed by 2225

Abstract

Hot working tool steels (HWTS) are popular for industrial applications such as injection molding tools, and casting dies because of their high wear resistance, fatigue, strength, and toughness properties, even at elevated temperatures. Conventionally, they go through multi-stage heat treatments in order to [...] Read more.

Hot working tool steels (HWTS) are popular for industrial applications such as injection molding tools, and casting dies because of their high wear resistance, fatigue, strength, and toughness properties, even at elevated temperatures. Conventionally, they go through multi-stage heat treatments in order to attain targeted microstructures. Achieving such microstructures with a laser powder bed fusion (LPBF) process will require tailor-made process parameters since it is characterized by non-equilibrium conditions, non-uniform temperature distribution, and metastable phase formation. Recent advances in the LPBF qualification of 1.2343/4 HWTS have shown commendable results but are still fraught with the limitations of poor ductility or extra post-heat treatment steps. For the industrial competitiveness of LPBF HWTS, the enhancement of strength and ductility and elimination of post processing is critical. Therefore, minimizing retained austenite in the as-built samples through pre-heat treatment or alloying to reduce post heat treatments without sacrificing strength will be economically important for industry. In this work, 1.2343 HWTS and its modified form were LPBF printed both in the as-built, pre- and post-heat-treated conditions. The results are discussed based on the correlations of the powder properties with LPBF—part density, microstructure, and mechanical properties. Full article

(This article belongs to the Special Issue Recent Advances in Processes and Design Methods for Additive Manufacturing)

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19 pages, 4640 KiB

Open AccessArticle

Investigating the Influence of Material Extrusion Rates and Line Widths on FFF-Printed Graphene-Enhanced PLA

by Javaid Butt, Raghunath Bhaskar and Vahaj Mohaghegh

J. Manuf. Mater. Process. 2022, 6(3), 57; https://doi.org/10.3390/jmmp6030057 - 24 May 2022

Cited by 6 | Viewed by 3369

Abstract

Fused filament fabrication (FFF) is a widely used additive manufacturing process that can produce parts from thermoplastics. Its ease of operation and wide variety of materials make it a popular choice for manufacturing. To leverage such benefits, the commonly used thermoplastics (e.g., PLA [...] Read more.

Fused filament fabrication (FFF) is a widely used additive manufacturing process that can produce parts from thermoplastics. Its ease of operation and wide variety of materials make it a popular choice for manufacturing. To leverage such benefits, the commonly used thermoplastics (e.g., PLA and ABS) are impregnated with nanoparticles, short or continuous fibers, and other additives. The addition of graphene nanoplatelets to PLA makes for a high-quality filament possessing enhanced mechanical, electrical, and thermal properties. Even with the advancement in materials, the optimisation of the process parameter remains the most complex aspect for FFF. Therefore, this study investigates the influence of two under-researched and overlooked processing parameters (material extrusion rates and line widths) on commercially available graphene-enhanced PLA (GPLA). Nine different material extrusion rates (70% to 150%) and five different line widths (0.2 mm to 1 mm) were used to manufacture GPLA specimens using a low-cost, desktop-based 3D printer, as per British and international standards. The study analyses the influence of these two processing parameters on mass, dimensional accuracy, surface texture, and mechanical properties of GPLA specimens. A non-destructive test has also been conducted and correlated with three-point flexural test to establish its applicability in evaluating flexural properties of GPLA. The results how that small line widths provide more accuracy with longer print times whereas large line widths offer more strength with shorter printing times. Increase in material extrusion rates adversely affect the surface finish and hardness but positively influence the flexural strength of GPLA specimens. The study shows that the manipulation of material extrusion rates and line widths can help designers in understanding the limitations of the default printing settings (100% material extrusion rate and 0.4 mm line width) on most desktop 3D printers and identifying the optimal combination to achieve desired properties using the FFF process. Full article

(This article belongs to the Special Issue Recent Advances in Processes and Design Methods for Additive Manufacturing)

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11 pages, 12939 KiB

Open AccessArticle

Additive Surface Graining in Prototype Tooling for Injection Molding

by Peter Burggräf, Georg Bergweiler, Josef Andrew Abrams and Anna Dunst

J. Manuf. Mater. Process. 2022, 6(3), 54; https://doi.org/10.3390/jmmp6030054 - 05 May 2022

Cited by 3 | Viewed by 3106

Abstract

Surface properties of injection molded parts have a strong effect on the visual and haptic perception of the parts by customers. Especially for injection molded automotive interior parts, grained surfaces can often be found. In conventional tooling, graining requires separate process steps. This [...] Read more.

Surface properties of injection molded parts have a strong effect on the visual and haptic perception of the parts by customers. Especially for injection molded automotive interior parts, grained surfaces can often be found. In conventional tooling, graining requires separate process steps. This makes the realization of grained injection molded prototype parts very complex. By additive manufacturing of injection molds in prototype tooling, it is possible to print micro structures into the mold surface in one printing operation. An injection mold with four different graining structures varying in depth and distance was designed and additively manufactured. The specification regarding the surface graining was analyzed by means of roughness measurements of the CAD model, injection mold and injection molded parts. Results show the feasibility of highly controllable additive surface graining. Full article

(This article belongs to the Special Issue Recent Advances in Processes and Design Methods for Additive Manufacturing)

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Review

Jump to: Research

42 pages, 11001 KiB

Open AccessReview

Liquid-Based 4D Printing of Shape Memory Nanocomposites: A Review

by Mohamad Alsaadi, Eoin P. Hinchy, Conor T. McCarthy, Vicente F. Moritz, Shuo Zhuo, Evert Fuenmayor and Declan M. Devine

J. Manuf. Mater. Process. 2023, 7(1), 35; https://doi.org/10.3390/jmmp7010035 - 31 Jan 2023

Cited by 10 | Viewed by 3968

Abstract

Significant advances have been made in recent years in the materials development of liquid-based 4D printing. Nevertheless, employing additive materials such as nanoparticles for enhancing printability and shape memory characteristics is still challenging. Herein, we provide an overview of recent developments in liquid-based [...] Read more.

Significant advances have been made in recent years in the materials development of liquid-based 4D printing. Nevertheless, employing additive materials such as nanoparticles for enhancing printability and shape memory characteristics is still challenging. Herein, we provide an overview of recent developments in liquid-based 4D printing and highlights of novel 4D-printable polymeric resins and their nanocomposite components. Recent advances in additive manufacturing technologies that utilise liquid resins, such as stereolithography, digital light processing, material jetting and direct ink writing, are considered in this review. The effects of nanoparticle inclusion within liquid-based resins on the shape memory and mechanical characteristics of 3D-printed nanocomposite components are comprehensively discussed. Employing various filler-modified mixture resins, such as nanosilica, nanoclay and nanographene, as well as fibrous materials to support various properties of 3D printing components is considered. Overall, this review paper provides an outline of liquid-based 4D-printed nanocomposites in terms of cutting-edge research, including shape memory and mechanical properties. Full article

(This article belongs to the Special Issue Recent Advances in Processes and Design Methods for Additive Manufacturing)

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