Additive 3D Printing Research Articles

Material Extrusion Additive Manufacturing of Wood and Lignocellulosic Filled Composites.

Wood and lignocellulosic-based material components are explored in this review as functional additives and reinforcements in composites for extrusion-based additive manufacturing (AM) or 3D printing. The motivation for using these sustainable alternatives in 3D printing includes enhancing material properties of the resulting printed parts, while providing a green alternative to carbon or glass filled polymer matrices, all at reduced material costs. Previous review articles on this topic have focused only on introducing the use of natural fillers with material extrusion AM and discussion of their subsequent material properties. This review not only discusses the present state of materials extrusion AM using natural filler-based composites but will also fill in the knowledge gap regarding state-of-the-art applications of these materials. Emphasis will also be placed on addressing the challenges associated with 3D printing using these materials, including use with large-scale manufacturing, while providing insight to overcome these issues in the future.

Additive manufacturing in drug delivery applications: A review.

The traditional healthcare method follows 'one-size-fits-all' criteria, which shows some limitations in rendering proper results due to varied pharmacokinetic traits of different patients. Each patient shows a different result to a set of prescribed medicines with respect to other patient. In addition, this empirical criterion is also vulnerable to develop unfavourable side-effects due to overdose or under-dose. The advancements in the field of pharmacogenetic testing has paved the way for searching solutions to achieve the goal of 'personalized medicine'. This concept has the potential to provide more effective results as compared to the traditional technique. The technology of additive manufacturing or 3D printing can cater the need of the patient-centric principle. A wide range of 3D printing techniques provide the independence to work with a number of bio-materials. This paper carries out a systematic review methodology based on the application of this novel technology in the field of drug delivery. The materials, methods of drug administration, techniques used for printing have been elaborated along with the manufacturing of polypills with varied release profiles and geometries. Certain in vivo studies has also been reported to assess the feasibility of this technology. The concept of 4D printing in this direction has also been discussed. Finally, some excerpts on estimated future scope have also been illustrated.

3D printed supercapacitor using porous carbon derived from packaging waste

• A 3D printed supercapacitor based on waste material is reported for the first time. • Electrode material is activated carbon derived from packaging waste. • Device shows highest capacitance among extrusion printed supercapacitors. There is considerable interest in developing sustainable fabrication technologies such as additive manufacturing or 3D printing for solid-state supercapacitors. The 3D printing of supercapacitors offers advantages such as rapid prototyping of 3D electrode structures that can improve device performance. Most of the efforts on 3D printing of such devices till date have faced some challenges including low capacitance shown by printed devices, significant post-processing on printed electrodes, and the use of non-additive fabrication methods to make the solid electrolyte. To better derive the benefits of 3D printing, it is important to address these challenges. In this paper, we demonstrate a solid-state supercapacitor made by extrusion-based 3D printing without post-processing, using a commercial 3D printer. Both the electrodes and electrolyte were 3D printed. The electrode material is activated carbon synthesized from packaging waste. The device shows a capacitance of 328.95 m F/cm 2 at 2.5 mA, the highest among all solid-state supercapacitors made by extrusion-based 3D printing till date. This capacity is attributed to the porous carbon used as active material, and the high loading of this carbon in the electrodes. To the best of our knowledge, this is the first report of a 3D printed solid-state supercapacitor using activated carbon derived from waste material. In the context of sustainable development of supercapacitors, the work described here represents a significant technological advance.

Chemical degradation of 3D printed products

This template describes the behavior of products created with additive 3D printing technology. The tested material used to produce the samples was polyactide acid (PLA). PLA is one of the most favourite material for 3D printing. This polylactide acid contains a metal additive. The standard dog-bone shaped samples reinforced with internal ribs arranged in a grid with 20% of the internal volume of the rib-filled sample were tested for tensile strength. The samples were subjected to different types of chemical degradation prior to the test. As a degradation agent, there was used an organic solvents. The result of the research is the effect of the degradation factor on the mechan-ical properties of these samples and possible use in practice, specifically in technology.

Characterization and Qualification of LPBF Additively Manufactured AISI-316L Stainless Steel Brackets for Aerospace Application

Additive manufacturing or 3D printing is recognized as a revolutionary type of processing to replace the traditionally fabricated components, including castings, wrought products and multiple piece assemblies thereof. 3D printing helps to realize complicated parts within a short time, with minimum material wastage and allowing higher level of design optimization. Two types of brackets in stainless steel AISI-316L grade for aerospace applications were realized through laser powder bed fusion method. Detailed characterization, analysis and structural testing were performed on the powder, test coupons and the component itself to qualify these brackets for the intended application. Significant amount of material removal, excessive machining time and associated problems such as residual stresses and warpage envisaged in the conventional manufacturing route have been avoided. The mechanical properties meet the requirements specified in ASTM F 3184-16 standard and were similar to or better than vis-a-vis that can be achieved through forged route manufacturing. Minor distortion was noticed on thin wall regions which have been avoided in the next hardware by distortion compensation and adding extra stock at thin sections which can be removed by minimum machining. Non-destructive testing was performed by macro CT and brackets were found to be free from defects > 100 µm. Further, there is scope for topology optimization through design for additive manufacturing (DfAM) and achieving weight savings for future requirements.

A review on machine learning in 3D printing: applications, potential, and challenges

Additive manufacturing (AM) or 3D printing is growing rapidly in the manufacturing industry and has gained a lot of attention from various fields owing to its ability to fabricate parts with complex features. The reliability of the 3D printed parts has been the focus of the researchers to realize AM as an end-part production tool. Machine learning (ML) has been applied in various aspects of AM to improve the whole design and manufacturing workflow especially in the era of industry 4.0. In this review article, various types of ML techniques are first introduced. It is then followed by the discussion on their use in various aspects of AM such as design for 3D printing, material tuning, process optimization, in situ monitoring, cloud service, and cybersecurity. Potential applications in the biomedical, tissue engineering and building and construction will be highlighted. The challenges faced by ML in AM such as computational cost, standards for qualification and data acquisition techniques will also be discussed. In the authors’ perspective, in situ monitoring of AM processes will significantly benefit from the object detection ability of ML. As a large data set is crucial for ML, data sharing of AM would enable faster adoption of ML in AM. Standards for the shared data are needed to facilitate easy sharing of data. The use of ML in AM will become more mature and widely adopted as better data acquisition techniques and more powerful computer chips for ML are developed.

A comprehensive review: metrology in additive manufacturing and 3D printing technology

Additive manufacturing (AM) is making a big leap in the manufacturing technology world primarily due to its unique capability to produce parts in a layer-by-layer fashion from the digital 3D model with immense versatility in terms of design complexity. In addition, AM does not require any additional tooling and can produce parts with minimal to no material loss. Despite these technological advantages, AM is not making inroads to its potential, mainly due to a lack of fundamental understanding of all the AM processes and cohesive efforts in standardization, metrology (the science of measurement), qualification and certification. As a result, AM produces parts with higher complexity and features yet lacking dimensional accuracy, precision, the required level of tolerances and intended material properties. Particularly, the process-specific standardized metrology and inspection methods for the parts made by AM play a major role in imparting the desired quality and subsequently facilitate the process of certification of the AM part. Considering this, the present article provides (1) a comprehensive review of generic metrology and in-situ, real-time inspection methods that are currently utilized for the parts produced from conventional manufacturing processes in use, as well as (2) a comprehensive review of metrology and in-situ, real-time inspection methods currently and/or may be utilized for the parts produced from AM processes. In addition to these, the appropriate metrology and inspection methods are recommended here for various AM processes. NSWC Corona, the leading agency for the U.S. Navy’s Metrology and Calibration (METCAL) program, is playing an important role towards addressing these AM metrology challenges.

Screening of pharmaceutical polymers for extrusion-Based Additive Manufacturing of patient-tailored tablets.

The main objective of this work was to explore the potential of coupling hot-melt extrusion (HME) to Fused Filament Fabrication (FFF), also known as Extrusion-Based Additive Manufacturing (EBAM) or 3D Printing, in order to manufacture 3D printed tablets with different release behavior from plasticizer-free filament matrices. The suitability of different thermoplastic polymers towards FFF was investigated, and a link between the mechanical properties of filaments produced by HME and the feeding performance into the FFF printer was established. Model drugs with different aqueous solubility (metoprolol tartrate and theophylline anhydrous) were processed with hydrophilic and hydrophobic polymers, and the influence of the formulation, drug concentration and applied process settings on the release kinetics was investigated. Filaments with up to 40% drug load were successfully extruded with a smooth surface and a diameter of 1.75±0.05mm. However, filaments with high brittleness and low toughness were broken by the feeding gears. In contrast, none of the filaments were squeezed aside by the gears, which indicated that they were sufficiently stiff as indicated by the high Young's moduli of all formulations. For all formulations, the release from the tablets with 50% infill degree was faster as compared to the tablets with 100% infill degree. Theophylline (20% w/w) release from Kollicoat® IR matrix was completed within 40min from 50% infill tablets. In contrast, 80% metoprolol tartrate was released from the hydrophobic Capa® 6506 polymer within 24hrs from 50% infill 3D tablets containing 40% w/w MPT.

Implementing Model‐Based Systems Engineering for the Development and Support of an Additive‐Layer Manufacturing Plant in the Aerospace Context

AbstractOne of the revolutionary changes of the 21st century in the aerospace industry is the emergence of Additive Layer Manufacturing or 3D printing technology. This is so for a number of reasons. There is virtually no material waste in the production process. Existing aircraft parts of current designs can be produced in less time and for a fraction of the cost, whilst still meeting the ‘form, fit and function’ requirements of those existing parts. Modified parts that are stronger and lighter, but which could not previously be produced with traditional manufacturing methods and tools, can be designed and produced. Going even beyond parts, new designs will increasingly be enabled with larger ALM machines that are capable of printing much larger components, which have most of the traditional parts already integrated. This dramatically reduces manufacturing and assembly times and costs, as well as weight, while increasing the level of functional integration by such components.This paper reports on the application of MBSE for the development and support of a new ALM Plant in the UK. The establishment of this ‘ALM System’ followed years of cutting‐edge research activities on laser and electron beam powder bed technologies. The requirements for and the solution architecture of the ALM System were developed using various methods and supporting tools, until the requirements cascade and part of the corresponding system design, down to the level of certain detailed production processes, was modeled in SysML using MagicDraw.

Additive Opto-Thermomechanical Nanoprinting and Nanorepairing under Ambient Conditions.

We demonstrate an opto-thermomechanical (OTM) nanoprinting method that allows us not only to additively print nanostructures with sub-100 nm accuracy but also to correct printing errors for nanorepairing under ambient conditions. Different from other existing nanoprinting methods, this method works when a nanoparticle on the surface of a soft substrate is illuminated by a continuous-wave (cw) laser beam in a gaseous environment. The laser heats the nanoparticle and induces a rapid thermal expansion of the soft substrate. This thermal expansion can either release a nanoparticle from the soft surface for nanorepairing or transfer it additively to another surface in the presence of optical forces for nanoprinting with sub-100 nm accuracy. Details of the printing mechanism and parameters that affect the printing accuracy are investigated. This additive OTM nanoprinting technique paves the way for rapid and affordable additive manufacturing or 3D printing at the nanoscale under ambient conditions.

Protocols for 3D-printing pieces by fused deposition modeling for research purposes: from modeling to post-printing treatment

Additive manufacturing or 3D-printing is a revolutionary technique for prototyping and building objects for final use. Since the first registers at ~1890 the improved technology has boosted the applications of such technique, decreasing its market price. The most affordable 3D-print technique is Fuse Deposition Modeling (FDM), which is based on a layer-by-layer deposition of a fused polymer on a cooled table. Although FDM has been used by industrials, students and researchers, there are few published protocols dealing with small challenges and daily problems. Here we use a basic object to detail pre- and post-printing steps. This technical note offers the reader tools to model, print and treat the 3D-object. We point out basic challenges, such as positioning the objects on the virtual table of the slicing software, that may lead towards undesirable printed pieces. The protocols described here do not cover the uncountable possibilities of 3D-printing by FDM, but surely help researchers and industrials to start working with it. DOI: http://dx.doi.org/10.30609/JETI.2020-8625

3D printing of clay for decorative architectural applications: Effect of solids volume fraction on rheology and printability

The effect of varying the solids volume fraction of an aqueous clay paste suspension on its printability via an Additive Manufacturing (AM) or 3D printing technique, Direct Ink Writing (DIW) or material extrusion, has been studied. DIW is a cost-effective and straightforward fabrication technology suitable for adoption at a larger scale by the traditional ceramics industry and the creative community. The pastes were prepared with volume fraction of solids ranging from 25–57 vol%. Their rheological properties (storage modulus and apparent yield stress) were measured by dynamic oscillatory rheometry. The relationships between solids content, rheological behaviour and print parameters were evaluated. An equation based on rheological properties to delineate between printable and non-printable conditions has been proposed. Several decorative pieces have been produced for architectural purposes.

Comparison of the Accuracy of Implant Position Using Surgical Guides Fabricated by Additive and Subtractive Techniques.

To evaluate the accuracy of implant position using surgical guides fabricated by additive and subtractive techniques. A partially edentulous standardized mandibular implant model with different bone densities and soft tissue was duplicated and a diagnostic wax-up was performed for the #30 area. A reference radiographic guide was fabricated and cone beam computed tomography (CBCT) was made with the reference radiographic guide in place. A surgical guide was designed using BlueSky Plan 4 software and a reference implant was placed in the #30 region. The STL file of the surgical guide was exported and specimens (n = 15) were fabricated by two different techniques: additive (3D printing) and subtractive (milling). The standardized mandibular model was surface-scanned and duplicated with printed dental model resin (n = 30). Each surgical guide was used to place an implant in thirty duplicate printed models. Differences in implant position as compared to the reference were measured from digital scans with scan bodies in place. The angular deviations, differences in depth, coronal and apical deviations were measured using GeoMagic Control X software. Results were analyzed by Wilcoxon-Mann-Whitney test and PERMANOVA (Permutational Multivariate Analysis of Variance). Intraclass correlation was used to assess measurement reproducibility with Bonferroni adjustment for multiple testing as needed (α = 0.05). There were no significant differences in accuracy of implant placement using guides fabricated using additive vs subtractive techniques. The mean angular deviations between the reference and actual position of implant in mesio-distal cross-section were 0.780 ± 0.80° for printed group and 0.77 ± 0.72° for the milled group. The differences in bucco-lingual cross-section were 1.60 ± 1.22° in in printed group and 1.77 ± 0.76° in the milled group. The differences in depth (mm) were measured at the top of the scan body at four locations: mesial, distal, buccal and lingual. The mean differences in depth for the group that used printed surgical guides were (mesial) 0.37 ± 0.29 mm, (distal) 0.32 ± 0.23 mm, (buccal) 0.24 ± 0.23 mm, and (lingual) 0.25 ± 0.17 mm. The mean differences in depth for the group that used milled surgical guides were (mesial) 0.51 ± 0.33 mm, (distal) 0.40 ± 0.32 mm, (buccal) 0.22 ± 0.23 mm, and (lingual) 0.23 ± 0.12 mm in those four aspects, respectively. The mean coronal deviation showed 0.32 mm in the printed group and 0.27 mm in the milled group. For the apical deviation, the results of this study showed mean apical deviation 0.84 mm in the printed group and 0.80 mm in the milled group. Results indicate that 3D-printed surgical guides are statistically as accurate as milled guides for guided-implant surgery with the benefits of high accuracy, ease of fabrication, less waste compared to subtractive techniques, and reduction of laboratory time thereby increasing cost-effectiveness.

Protocols for 3D-printing pieces by fused deposition modeling for research purposes: from modeling to post-printing treatment

Additive manufacturing or 3D-printing is a revolutionary technique for prototyping and building objects for final use. Since the first registers at ~1890 the improved technology has boosted the applications of such technique, decreasing its market price. The most affordable 3D-print technique is Fuse Deposition Modeling (FDM), which is based on a layer-by-layer deposition of a fused polymer on a cooled table. Although FDM has been used by industrials, students and researchers, there are few published protocols dealing with small challenges and daily problems. Here we use a basic object to detail pre- and post-printing steps. This technical note offers the reader tools to model, print and treat the 3D-object. We point out basic challenges, such as positioning the objects on the virtual table of the slicing software, that may lead towards undesirable printed pieces. The protocols described here do not cover the uncountable possibilities of 3D-printing by FDM, but surely help researchers and industrials to start working with it.
 
 DOI: http://dx.doi.org/10.30609/JETI.2020-8625

Modelling of an Additive 3D-Printing Process Based on Design of Experiments Methodology

Purpose: The implementation of additive manufacturing (AM) or 3D-printer manufacturing for technical prototyping, preproduction series and short production series can bring benefits in terms of reducing cost and time to market in product development. These technologies are beginning to be applied in different industrial sectors and have a great possibility of development. As these technologies are still in development, there is a need to define the capacity of the 3D machines to establish minimum standards for producing high-quality parts.Methodology/Approach: The proposed methodology is based on a design of experiments (DOE) approach, which serves as a guide for engineers when it comes to executing any experimental study. The following steps were followed (Unzueta et al., 2019): Phase 1: define; Phase 2: measure; Phase 3: plan; Phase 4: execute experimentation; Phase 5: analyse the results; Phase 6: improve via confirmation experiments; Phases 7-8: control and standardise.Findings: The proposed methodology is based on a design of experiments (DOE) approach, which serves as a guide for engineers when it comes to executing any experimental study. The following steps were followed (Unzueta et al., 2019): Phase 1: define; Phase 2: measure; Phase 3: plan; Phase 4: execute experimentation; Phase 5: analyse the results; Phase 6: improve via confirmation experiments; Phases 7-8: control and standardise.Originality/Value of paper: This study uses a methodological approach to demonstrate how the 3D printing technology can be enriched with statistical testing techniques (DOE). It defines numerical prediction models to obtain high-quality parts with a new AM technology, using a planning process with a minimum amount of experimentation.

Characterizing cement mixtures for concrete 3D printing

The need to automate the construction process for civil infrastructures has been ceaselessly propelled by the reported number of detrimental site accidents, enormous time, and material wastages in current labor-intensive approaches. Additive 3D printing could revolutionize the construction-site. Notable advantages of concrete 3D printing include wider build customizability, safer work ambiance, reduced construction time and cost. The major challenge in concrete printing is to identify and maintain the mixture characteristics suitable for printing and stacking up in layers. In this study, ready-to-print fresh cementitious mixtures with silica fume and superplasticizer were characterized for printability based on their rheological properties.

Surface modification and tribological behavior of plasma nitrided Inconel 718 manufactured via direct melting laser sintering method

Currently employed in aerospace, defense, oil, and gas applications, Inconel 718 (IN718) is an indispensable alloy with excellent thermo-mechanical properties and hot corrosion resistance. Inconel (IN718) has become the gold standard to manufacture turbine blades, bearing housing parts, compressor seals, drive couple gears, side pocket mandrels, wellheads, packers, and safety valves. Additive Manufacturing (AM) or 3D printing technology is a promising alternative to fabricate and repair nickel-based superalloy components, characterized by challenging processing through conventional methods due to the mechanical strength of the alloys or the geometric complexity of the piece. Furthermore, many applications require surface protection features, such as high hardness, corrosion, and wear resistance. These properties can be achieved by applying hard coatings and/or surface thermochemical treatments such as plasma nitriding. This study reports the effect of plasma nitriding applied on Laser Powder Bed Fusion (LPBF) additively manufactured IN718. Depending on the time, the treatment produced a 1.5–2.8 μm nitrided protective bi-layer composed by an outer CrN containing layer followed by an inner austenitic expanded γN layer. The growing kinetics analysis shows that the nitriding process follows a parabolic behavior. The nitriding process also increases the surface roughness as a result of case hardening formation reaching ~ 60 nm within 2 h. No measurable wear on the plasma nitrided additively manufactured IN718 alloy was recorded.

Additive manufacturing for energy storage: Methods, designs and material selection for customizable 3D printed batteries and supercapacitors

Abstract Additive manufacturing and 3D printing in particular have the potential to revolutionize existing fabrication processes, where objects with complex structures and shapes can be built with multifunctional material systems. For electrochemical energy storage devices such as batteries and supercapacitors, 3D printing methods allows alternative form factors to be conceived based on the end use application need in mind at the design stage. Additively manufactured energy storage devices require active materials and composites that are printable, and this is influenced by performance requirements and the basic electrochemistry. The interplay between electrochemical response, stability, material type, object complexity and end use application are key to realising 3D printing for electrochemical energy storage. Here, we summarise recent advances and highlight the important role of methods, designs and material selection for energy storage devices made by 3D printing, which is general to the majority of methods in use currently.

Architected porous metals in electrochemical energy storage

Porous metallic structures are regularly used in electrochemical energy storage devices as supports, current collectors or active electrode materials. Bulk metal porosification, dealloying, welding or chemical synthesis routes involving crystal growth or self-assembly for example, can sometimes provide limited control of porous length scale, ordering, periodicity, reproducibility, porosity and surface area. Additive manufacturing and 3D printing has shown the potential to revolutionize the fabrication of architected metals many forms, allowing complex geometries not usually possible by traditional methods, but enabling complete design freedom of a porous metal based on the required physical or chemical property to be exploited. We discuss properties of porous metal structures in EES devices and provide some opinions on how architected metals may alleviate issues with electrochemically active porous metal current collectors, and provide opportunities for optimum design based on electrochemical characteristics required by batteries, supercapacitors or other electrochemical devices.

Global Diffusion of Innovation during the Fourth Industrial Revolution: The Case of Additive Manufacturing or 3D Printing

Additive manufacturing can be considered an innovative and high-technology and one of its characteristics is that it has limited dependency on the location. The purpose of this study is to examine this aspect by investigation how additive manufacturing is spreading globally. The focus is on established manufacturers of industrial additive manufacturing machines. It was found that the early-stage diffusion of this technology is primarily in advanced economies. Furthermore, many of the currently established companies that manufacture industrial 3D printers come from already existing companies that expanded into AM or that led to spin-off companies. The complexity of AM which requires expert knowledge across a range of fields may be the key reason for this finding. Recommendations for further research are provided.