Polymer-based Additive Manufacturing Research Articles

Exploring Polymer-Based Additive Manufacturing for Cost-Effective Stamping Devices: A Feasibility Study with Finite Element Analysis.

This research investigates the feasibility of manufacturing stamping devices using Material Extrusion (MEX) Additive Manufacturing (AM) technology, traditionally fabricated from metal, to reduce production costs and time. This study examines polymer-based devices subjected to Finite Element Analysis (FEA) to evaluate their performance in stamping metal sheets of varying thicknesses. The findings reveal that ABS polymer devices, while demonstrating potential, operate near the material's limit under compression forces, particularly for sheet thicknesses up to 1 mm. Specifically, differences of 0.7 mm were observed at the connection radii of 0.25 mm sheets and 1.4 mm for 0.5 mm sheets, with angular deviations of 1.5 degrees for 0.25 mm sheets and 4 degrees for 0.5 mm sheets. Additionally, devices made of Nylon were deemed suitable for reduced-thickness sheets (0.25 mm), performing better than those made of ABS. These results suggest that while ABS devices exhibit significant deviations (up to 45 degrees for 1 mm sheets), the method shows promise for small batch production and prototyping. Further optimisation through material enhancements and mechanical improvements is recommended to minimise deformations and enhance precision.

Surface Finish Optimization of Vapor Smoothened PLA Fabricated Parts with Microstructural Analysis

Additive Manufacturing (AM) is a product creation method done layer-by-layer. This process tends to create an unwanted feature known as staircase effect. Vapor smoothing is considered a viable solution for polymer-based AM products to minimized surface roughness. Research literature concerning vapor smoothing of polylactic acid (PLA) parts generally limited unlike its ABS counterpart. This research aims to identify optimum level for both chamber temperature and exposure time of the AM product. Two methods were used to compare their outputs with one another. The two methods are surface roughness tester and optical microscopy. The results provided an impressive 50.88 and 62.72% improvement based on the two test methods. Lastly, a contour-plot was generated to provide future users a guideline if they want to conduct research similar study.

Mechanism-Based damage and failure of Fused Filament Fabrication components

Fused Filament Fabrication (FFF) is a polymer-based Additive Manufacturing (AM) technology that produces complex layered components. The characterization of the inherited orthotropic properties of FFF components and their failure analysis is a challenging endeavor. In this paper, the failure mechanics of FFF parts are studied via a Mechanism-Based (MB) damage material model. A MB damage criterion is developed by considering that the damage is driven by different failure modes identified according to the printing pattern. The developed criterion is compared to the Tsai–Wu (TW) criterion, which is commonly used for orthotropic materials with different strengths in tension and compression. Also, a MB cracking model that incorporates the orthotropic brittleness of FFF components is developed. The application of this cracking model requires solely two parameters to be defined.Numerical predictions of the cracking of two different experimental tests illustrate the similarities and the differences between the MB and TW damage criteria. The results demonstrate that the MB damage criterion can accurately match the experimental results, while the TW criterion fails to describe correctly the failure modes in complex 3D stress states.

Dimensional Methods Used in the Additive Manufacturing Process.

It is a well-known fact that in the field of modern manufacturing processes, additive manufacturing (AM) offers unexpected opportunities for creativity and rapid development. Compared with classical manufacturing technologies, AM offers the advantages of reducing weight and improving performance and offers excellent design capabilities for prototyping and rapid sample manufacture. To achieve its full potential regarding cost, durability, material consumption, and rigidity, as well as maintaining competitiveness, there are several research directions that have not been explored. One less frequently explored direction is the involvement of dimensional methods in obtaining an optimal and competitive final product. In this review, we intend to discuss the ways in which dimensional methods, such as geometric analogy, similarity theory, and dimensional analysis, are involved in addressing the problems of AM. To the best of our knowledge, it appears that this field of engineering has not fully maximized the advantages of these dimensional methods to date. In this review, we survey mainly polymer-based AM technology. We focus on the design and optimization of highly competitive products obtained using AM and also on the optimization of layer deposition, including their orientation and filling characteristics. With this contribution to the literature, we hope to suggest a fruitful direction for specialists involved in AM to explore the possibilities of modern dimensional analysis.

3D Printing of sustainable coal polymer composites: Thermophysical characteristics

Recently, there has been a growing interest in enlisting polymer-based additive manufacturing in high-volume structural applications such as wind turbine blade tooling and additive housing construction. However, the availability of sustainable and environmentally friendly 3D printable materials could present a serious challenge, precluding the technology expansion to such applications. This research was focused on developing sustainable and environmentally friendly coal-plastic composites for use in high-volume applications. Polylactic acid, polyethylene terephthalate glycol, high-density polyethylene, and polyamide-12 resins were melt-mixed with bituminous Pittsburgh No. 8 coal at loadings varying from 20 wt % to 70 wt % coal. Thermoplastic composite filaments were extruded and processed with commercial 3D printers. Important thermophysical properties including coefficients of thermal expansion, heat deflection temperatures, glass transition and melt temperatures, specific heat capacities, thermal conductivities, and thermal stabilities of the coal-plastic composites were investigated. Coefficient of thermal expansion values for the composites had an inverse relationship with coal content lending to decreased print warping and consistent 3D printing of high-density polyethylene materials. Coal increased the heat deflection temperature of high-density polyethylene composites while little to no effect was observed for the other plastics. All composites maintained comparable melt temperatures, allowing for processing with commercial equipment. Specific heat capacity and thermal conductivity decreased with coal loading for all composite materials. Thermogravimetric analysis under air showed that the introduction of coal improved the thermal stability of all plastics by increasing the decomposition temperatures at 5 % and 50 % weight loss and by reducing the maximum decomposition rates.

Development of a Reactive Force Field for Simulating Photoinitiated Acrylate Polymerization.

Light-driven and photocurable polymer-based additive manufacturing (AM) has enormous potential due to its excellent resolution and precision. Acrylated resins that undergo radical chain-growth polymerization are widely used in photopolymer AM due to their fast kinetics and often serve as a departure point for developing other resin materials for photopolymer-based AM technologies. For successful control of the photopolymer resins, the molecular basis of the acrylate free-radical polymerization has to be understood in detail. We present an optimized reactive force field (ReaxFF) for molecular dynamics (MD) simulations of acrylate polymer resins that captures radical polymerization thermodynamics and kinetics. The force field is trained against an extensive training set including density functional theory (DFT) calculations of reaction pathways along the radical polymerization from methyl acrylate to methyl butyrate, bond dissociation energies, and structures and partial charges of several molecules and radicals. We also found that it was critical to train the force field against an incorrect, nonphysical reaction pathway observed in simulations that used parameters not optimized for acrylate polymerization. The parameterization process utilizes a parallelized search algorithm, and the resulting model can describe polymer resin formation, crosslinking density, conversion rate, and residual monomers of the complex acrylate mixtures.

Polymer-Based Additive Manufacturing for Orthotic and Prosthetic Devices: Industry Outlook in Canada.

The conventional manufacturing methods for fabricating orthotic and prosthetic (O&P) devices have been in practice for a very long time. Recently, O&P service providers have started exploring different advanced manufacturing techniques. The objective of this paper is to perform a mini review on recent progress in the use of polymer-based additive manufacturing (AM) for O&P devices and to gather insights from the O&P professionals on the current practices and technologies and on the prospect of using AM techniques in this field. In our study, first, scientific articles on AM for O&P devices were studied. Then, twenty-two (22) interviews were conducted with O&P professionals from Canada. The primary focus was on five key areas: cost, material, design and fabrication efficiency, structural strength, functionality, and patient satisfaction. The cost of manufacturing the O&P devices using AM techniques is lower as compared to the conventional methods. O&P professionals expressed their concern over the materials and structural strength of the 3D-printed prosthetic devices. Published articles report comparable functionality and patient satisfaction for both O&P devices. AM also greatly improves design and fabrication efficiency. However, due to a lack of qualification standards for 3D printed O&P devices, 3D printing is being embraced more slowly in the O&P business than in other industries.

Millimeter-Wave Near-Field Evaluations of Polylactic Acid (PLA) Filament Used in Polymer-Based Additive Manufacturing (AM)

ABSTRACT Additive manufacturing (AM) remains to be a rapidly growing industry with applications that are extended beyond metals and to other materials, such as polymers, ceramics, and concrete, to name a few. However, advancement in the development of inspection techniques, particularly in-line nondestructive testing (NDT) methods, lags significantly. Most of the research in developing such methods has focused on metal-based AM. This paper investigates the efficacy of three high-resolution near-field millimeter-wave probes for detecting small voids in the feedstock polymeric filaments used for AM. The electromagnetic (EM) design and optimization of these probes are discussed in this paper. The design of the probes is based on concentrating the interrogating electric field of an open-ended waveguide in a small region corresponding to the area of a thin dielectric slab insert. This results in achieving a higher spatial resolution than when using only the open-ended waveguide. Extending the dielectric slab to an optimum value out of the waveguide makes the electric field more concentrated and potentially further improves the spatial resolution. These modifications also reduce the detection sensitivity as a function of increasing standoff distance. However, the spatial resolution of these probes varies more rapidly as the standoff distance increases. Subsequently, the efficacy of these three probes was studied and compared using a comprehensive set of numerical EM simulations at V-band (50–75 GHz). Afterward, three such probes were fabricated, at V-band (50–75 GHz), and were used to measure the reflection responses of the stock Polylactic Acid (PLA) filaments with a very small hemispherical surface void. Root-Mean-Squared-Error (RMSE), between reference and defective filaments and over the simulated and measured frequency range, was calculated as a criterion to compare the detection capability of the three probes in the entire frequency band. The results showed that at V-band (50–75 GHz) the spatial resolution of the standard open-ended rectangular waveguide is deemed sufficient detecting small surface voids of the stock PLA filaments.

Aluminum foams with complex pore topologies for acoustical applications

Metal foams are used in various industries due to the great variety of properties they possess such as high strength-to-weight ratio, high energy absorption, and the ability to endure extreme conditions. However, despite their desirable properties, traditional metal foams lack acoustic absorption properties because of their stochastic open porous structure—a function of the foaming process. Additive manufacturing (AM) can allow the fabrication of more complex foams; however, current metal AM methods provide significant processing and scalability challenges, especially in printing aluminum parts. Here, we present an alternative method for fabricating open-celled aluminum sound absorbers with controlled cellular architectures. The method relies on modeling the cellular templates using an implicit, field-based modeling method. The templates are then fabricated by combining polymer-based AM techniques and converted into aluminum Duocel® foams using ERG Aerospace Corporation’s proprietary foaming technology. The acoustical properties of the fabricated foams are then measured using a normal incidence impedance tube method. Our results show that this method allows the fabrication of highly complex cellular architectures that may be optimized to obtain application-specific multifunctional performance.

Stiffness Degradation of PolyJet Printed Nano Embedded Configuration with Digital Material

Introduction: Polymer-based additive manufacturing (AM) parts are used in a variety of engineering applications in the automotive, aerospace, and energy industries. However, AM printed parts are a new class of materials and the structural performance of these materials is not yet fully understood, and research on the exact performance of PolyJet printed parts and related digital materials under fatigue loading is still minimal. The present study provides insight into the fatigue damage state, cyclic performance, and comparison between pristine (baseline) and Carbon Nano Fibers (CNFs) modified embedded test coupons formed using tailored digital designs and printed with digital polypropylene from PolyJet printing. Methods: The investigations employed 3-dimensional (3D) test coupons formed using PolyJet printing. The nanomodified coupons were formed using digital design configurations for tailored deposition locations that allowed the integration in a 2-step process. The limitations of the conventional ASTM D638 2-dimensional (2D) test coupon for AM-treated materials caused by the process are eliminated by the homogeneous 3D test coupon used in this work. An analytical model of the accumulated damage state based on stiffness deterioration under cyclic loading is presented along with an empirical model of effective elastic modulus based on the analysis of fatigue data. Additionally, the predicted model and the actual damage accumulation due to cyclic loading are compared. Results: With a high correlation coefficient, R2 of 0.9971 for the baseline and 0.9885 for the CNFs embedded configuration, it is observed that the linear function model can estimate fatigue life with an agreement to experimental results and can be used to extrapolate for other stress levels. CNFs modified resin embedded configuration showed lower fatigue life as compared to baseline. This reduction can be attributed to the stress concentration at the interfaces. Conclusion: This work fills the gap in the literature by characterizing the fatigue life, and cyclic performance of PolyJet printed parts and nano-modified systems with digital material.

Reading Direct-Part Marking Data Matrix Code in the Context of Polymer-Based Additive Manufacturing.

A novel approach to detect and decode direct-part-marked, low-contrast data matrix codes on polymer-based selective laser sintering manufactured parts, which is able to work on lightweight devices, is presented. Direct-part marking is a concept for labeling parts directly, which can be carried out during the additive manufacturing's design process. Because of low contrast in polymer-based selective laser sintering manufactured parts, it is a challenging task to detect and read codes on unicolored parts. To achieve this, at first, codes are located using a deep-learning-based approach. Afterwards, the calculated regions of interest are passed into an image encoding network in order to compute readable standard data matrix codes. To enhance the training process, rendered images, improved with a generative adversarial network, are used. This process fulfills the traceability task in assembly line production and is suitable for running on mobile devices such as smartphones or cheap sensors placed in the assembly line. The results show that codes can be localized with 97.38% mean average precision, and a readability of 89.36% is achieved.

Exploring Machine Learning-Based Fault Monitoring for Polymer-Based Additive Manufacturing: Challenges and Opportunities

Three-dimensional printing, often known as additive manufacturing (AM), is a groundbreaking technique that enables rapid prototyping. Monitoring AM delivers benefits, as monitoring print quality can prevent waste and excess material costs. Machine learning is often applied to automating fault detection processes, especially in AM. This paper explores recent research on machine learning-based mechanical fault monitoring systems in fused deposition modeling (FDM). Specifically, various machine learning-based algorithms are applied to measurements extracted from different parts of a 3D printer to diagnose and identify faults. The studies often use mechanical-based fault analysis from data gathered from sensors that measure attitude, acoustic emission, acceleration, and vibration signals. This survey examines what has been achieved and opens up new opportunities for further research in underexplored areas such as SLM-based mechanical fault monitoring.

An overview of additive manufacturing methods, materials, and applications for flexible structures

Various types of additive manufacturing (AM) methods (also called 3D printing), and materials have been increasingly studied in the field of additive manufacturing of flexible structures such as fabrics, and flexible electronics. Polymer-based AM processes allow the flexibility, rapid, and low-cost fabrication of complex geometries depending on the types of materials used. The purpose of this review article is to summarize the major AM methods, materials, and their emerging applications to additively manufacture the flexible structures. In the AM methods section, Fused Deposition Modeling (FDM), and Selective Laser Sintering (SLS) are reviewed for fabrics, and Direct Ink Writing (DIW) for electronics. In the Materials section, the manufacturing methods, chemical structures, properties, advantages, and limitations of some of the widely used materials in three-dimensional (3D) printing of polymers are reviewed. Third, the applications of these methods and materials for fabrics, and electronics are covered. Finally, the associated opportunities and challenges in 3D printing process of flexible structures are described. The future research should be related to the exploration of combinations and development of innovative materials, printing process parameters, detail study on improving the properties, and hybrid 3D printing process.

3-D Printed Plug and Play Prototyping for Low-Cost Sub-THz Subsystems

Polymer-based additive manufacturing using 3-D printing for upper-millimeter-wave ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ca.</i> 100 to 300 GHz) frequency applications is now emerging. Building on our previous work, with metal-pipe rectangular waveguides and free-space quasi-optical components, this paper brings the two media together at G-band (140 to 220 GHz), by demonstrating a compact multi-channel front-end subsystem. Here, the proof-of-concept demonstrator integrates eight different types of 3-D printed components (30 individual components in total). In addition, the housing for two test platforms and the subsystem are all 3-D printed as single pieces, to support plug and play development; offering effortless component assembly and alignment. We introduce bespoke free-space TRM calibration and measurement schemes with our quasi-optical test platforms. Equal power splitting plays a critical role in our multi-channel application. Here, we introduce a broadband 3-D printed quasi-optical beamsplitter for upper-millimeter-wave applications. Our quantitative and/or qualitative performance evaluations for individual components and the complete integrated subsystem, demonstrate the potential for using consumer-level desktop 3-D printing technologies at such high frequencies. This work opens-up new opportunities for low-cost, rapid prototyping and small-batch production of complete millimeter-wave front-end subsystems.

Thermomechanical behavior of polymeric periodic structures

Additive manufacturing (AM) enables the fabrication of periodic structures with regular repeat units and tailorable mechanical properties. Polymer-based AM processes, such as fused filament fabrication (FFF), permit rapid, low-cost fabrication of periodic structures from a wide range of materials. However, the mechanical properties of polymers are strongly affected by temperature, especially near the glass transition temperature (T g ), which has a significant impact on the design and application of the structures. Herein, we utilize a coupled experimental and computational approach to evaluate the mechanical behavior of polymeric periodic structures (PPS) with uniform and spatially varying temperatures that span T g . Individual unit cells (square, auxetic, and honeycomb) are additively manufactured from polylactic acid (PLA) (T g = 54 °C) and experimentally evaluated by dynamic mechanical analysis (DMA) using a tension test fixture and thermal chamber. The unit cells are subjected to sequential tension and compression tests, up to a maximum of +/−20% strain, which are repeated from 40 °C to 65 °C in 5 °C increments. Maximum forces vary by two orders of magnitude when temperature varies across T g , and a hysteresis loop is observed for temperatures 14 °C below T g . This indicates that viscoelasticity has a significant impact on the mechanical properties of the structure below T g and that the structures are capable of dissipating energy. Experimental force-displacement and energy dissipation results agree favorably with results from a multiphysics finite element framework, which utilizes bulk material properties as inputs. The computational framework is then applied to structures comprising tessellated unit cells to evaluate the effects of uniform temperatures and temperature gradients on mechanical properties. The results demonstrate that non-uniform temperature fields can produce spatial variation of mechanical properties, such as Poisson’s ratio, throughout the structure. Insight obtained in this investigation provides guidelines for the design, fabrication, and implementation of PPS operating across a range of temperatures that passively modifies their mechanical properties and energy dissipation characteristics. • Thermomechanical analysis of square, honeycomb, and auxetic periodic structures. • Experimental and computational analysis of 3D printed PLA across glass transition. • Thermal gradients spatially affect array mechanical properties (Poisson’s ratio). • Square unit cell and honeycomb array dissipate highest energy per unit mass. • Applicable to other polymers and structures by updating bulk finite element inputs.

Recent Advances in Polymer-based 3D Printing for Wastewater Treatment Application: An Overview

The introduction of Industrial Revolution (IR) 4.0 has signalled a transformation of traditional manufacturing landscape to intelligent production systems and advanced technologies. Additive manufacturing (AM) is a vital element in this latest revolution due to its remarkable potential in providing a green fabrication alternative with advanced design flexibility that surpasses the traditional manufacturing methods. At present, polymer-based additive manufacturing has drawn considerable interest in wastewater research due to its notable design freedom in manufacturing of novel, geometrically complex, and porous structures used in membrane modules and spacers, adsorption, advanced oxidation process, bioreactor, and microfluidic technology. In this work, recent advances of additively manufactured polymeric materials and 3D printing techniques used for various wastewater research are reviewed. Furthermore, the challenges in the fabrication techniques are assessed, alongside with the discussion on future perspectives of polymer-based AM technologies to develop a versatile and sustainable wastewater treatment system at commercial scale.

Polymer-Based Additive Manufacturing: Process Optimisation for Low-Cost Industrial Robotics Manufacture

The robotics design process can be complex with potentially multiple design iterations. The use of 3D printing is ideal for rapid prototyping and has conventionally been utilised in concept development and for exploring different design parameters that are ultimately used to meet an intended application or routine. During the initial stage of a robot development, exploiting 3D printing can provide design freedom, customisation and sustainability and ultimately lead to direct cost benefits. Traditionally, robot specifications are selected on the basis of being able to deliver a specific task. However, a robot that can be specified by design parameters linked to a distinctive task can be developed quickly, inexpensively, and with little overall risk utilising a 3D printing process. Numerous factors are inevitably important for the design of industrial robots using polymer-based additive manufacturing. However, with an extensive range of new polymer-based additive manufacturing techniques and materials, these could provide significant benefits for future robotics design and development.

Mechanical and fatigue performance of pressurized vessels fabricated with Multi Jet Fusion™ for automotive applications

Multi Jet Fusion™ (MJF) is a new proprietary form of Additive Manufacturing (AM) from Hewlett Packard (HP) developed to manufacture structures with design and functional complexity while simultaneously providing a dramatic increase in the production rate relative to other forms of polymer-based AM. The increased rate is now enabling more efficient production of mid-volume products, and coupled with the additional benefits of geometric freedom, the technology is particularly well suited for the fabrication of complex manifold gas delivery systems. This paper describes a comprehensive study to evaluate the utility of MJF structures for maintaining pressures under static and dynamic conditions. The static pressure and gas confinement was applied to cylindrical structures at 345 and 689 kPa and pressure drops were measured in real-time. Similarly, fatigue pressure testing was performed for 10 5 cycles under 1724 kPa, and the cylinders demonstrated to be effective at maintaining a constant pressure under both ambient and high temperature (90 °C) conditions. Additional analyses relevant to the automotive industry were performed and included (a) gas permeation testing conducted with oxygen and carbon dioxide gas to study the gas storage performance on printed Polyamide-12 and (b) an oil chemical exposure experiment was performed to investigate mechanical performance degradation.

Additively manufactured respirators: quantifying particle transmission and identifying system-level challenges for improving filtration efficiency

The COVID-19 pandemic has disrupted the supply chain for personal protective equipment (PPE) for medical professionals, including N95-type respiratory protective masks. To address this shortage, many have looked to the agility and accessibility of additive manufacturing (AM) systems to provide a democratized, decentralized solution to producing respirators with equivalent protection for last-resort measures. However, there are concerns about the viability and safety in deploying this localized download, print, and wear strategy due to a lack of commensurate quality assurance processes. Many open-source respirator designs for AM indicate that they do not provide N95-equivalent protection (filtering 95% of SARS-CoV-2 particles) because they have either not passed aerosol generation tests or not been tested. Few studies have quantified particle transmission through respirator designs outside of the filter medium. This is concerning because several polymer-based AM processes produce porous parts, and inherent process variation between printers and materials also threaten the integrity of tolerances and seals within the printed respirator assembly. No study has isolated these failure mechanisms specifically for respirators. The goal of this paper is to measure particle transmission through printed respirators of different designs, materials, and AM processes. The authors compare the performance of printed respirators to N95 respirators and cloth masks. Respirators in this study printed using desktop- and industrial-scale fused filament fabrication processes and industrial-scale powder bed fusion processes were not sufficiently reliable for widespread distribution and local production of N95-type respiratory protection. Even while assuming a perfect seal between the respirator and the user’s face, although a few respirators provided >90% efficiency at the 100−300 nm particle range, almost all printed respirators provided <60% filtration efficiency. Post-processing procedures including cleaning, sealing surfaces, and reinforcing the filter cap seal generally improved performance, but the printed respirators showed similar performance to various cloth masks. The authors further explore the process-driven aspects leading to low filtration efficiency. Although the design/printer/material combination dictates the AM respirator performance, the identified failure modes originate from system-level constraints and are therefore generalizable across multiple AM processes. Quantifying the limitations of AM in producing N95-type respiratory protective masks advances understanding of AM systems toward the development of better part and machine designs to meet the needs of reliable, functional, end-use parts.

Full Issue Download Vol. 13 No. 1 2021 The Importance of the Measurement Infrastructure in Economic Recovery from the COVID-19 Pandemic Richard J. C. Brown , Fiona Auty, Eugenio Renedo, Mike King NCSLI Measure | Vol. 13 No. 1 (2021) | doi.org/10.51843/measure.13.1.1 Publisher NCSL International | Published February 2021 | Pages 18-21 Abstract: This paper describes the many, evidenced-based benefits

Facilitating the uptake of established methodologies for risk-based decision-making in product conformity assessment taking into account measurement uncertainty by providing dedicated software is the aim of the European project EMPIR CASoft(2018–2020), involving the National Measurement Institutes from France, Sweden and the UK, and industrial partner Trescal (FR) as primary supporter. The freely available software helps end-users perform the required risk calculations in accordance with current practice and regulations and extends that current practice to include bivariate cases. The software is also aimed at supporting testing and calibration laboratories in the application of the latest version of the ISO/IEC 17025:2017 standard, which requires that“…the laboratory shall document the decision rule employed, taking into account the level of risk […] associated with the decision rule and apply the decision rule.” Initial experiences following launch of the new software in Spring 2020 are reported.