Control of Process Settings for Large-Scale Additive Manufacturing With Sustainable Natural Composites

2018 ◽  
Author(s):  
Yadunund Vijay ◽  
Naresh D. Sanandiya ◽  
Stylianos Dritsas ◽  
Javier G. Fernandez
Keyword(s):  
Tensile Strength ◽  
Additive Manufacturing ◽  
Large Scale ◽  
Dimensional Accuracy ◽  
Strength Properties ◽  
Operating Point ◽  
Cross Sectional ◽  
Layer Spacing ◽  
Controllable Process ◽  
Face Centered

We present an additive manufacturing system for 3D printing large-scale objects using natural bio-composite materials. The process, affine to the Direct Ink Writing method, achieves build rate of 2.5cm3/s using a precision dispensing unit mounted on an industrial six-axis robot. During deposition the composite is wet and exhibits thixotropy. As it loses moisture it hardens and shrinks anisotropically. This paper highlights work on controlling the process settings to print filaments of desired dimensions while constraining the operating point to a region where tensile strength is maximum while shrinkage is minimum. Response surface models relating the controllable process settings such as Robot Linear Velocity, Material Feed Rate and Nozzle Offset, to the geometric and physical properties of an extruded filament, are obtained through Face-centered Central Composite Designed experiments. Unlike traditional applications of this technique which involve identifying a fixed optimal operating point, we use these models to first uncover the possible dimensions of a filament that can be obtained within operating boundaries of our system. Process setting predictions are then made through multi-objective optimization of the mathematical models. An interesting outcome of our study is the ability to produce filaments of different shrinkage and tensile strength properties, by solely changing process settings. As a follow up, we identify the optimal lateral overlap and inter-layer spacing parameters to define toolpaths to print 3D structures. If unoptimized, the material’s anisotropic shrinkage and non-linear compression characteristics cause severe delamination, cross-sectional tapering and warpage. Lastly, we show the linear scalability of our shrinkage model in 3D space which allows us to suitably compensate toolpaths to significantly improve dimensional accuracy of 3D printed artifacts.

Control of Process Settings for Large-Scale Additive Manufacturing With Sustainable Natural Composites

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Yadunund Vijay ◽  
Naresh D. Sanandiya ◽  
Stylianos Dritsas ◽  
Javier G. Fernandez
Keyword(s):  
Tensile Strength ◽  
Large Scale ◽  
Dimensional Accuracy ◽  
Interlayer Spacing ◽  
Strength Properties ◽  
Operating Point ◽  
Additive Manufacture ◽  
Cross Sectional ◽  
Face Centered ◽  
Nonlinear Compression

We present a system for 3D printing large-scale objects using natural biocomposite materials, which comprises a precision extruder mounted on an industrial six-axis robot. This paper highlights work on controlling process settings to print filaments of desired dimensions while constraining the operating point to a region of maximum tensile strength and minimum shrinkage. Response surface models relating the process settings to the geometric and physical properties of extruded filaments are obtained through face-centered central composite designed experiments. Unlike traditional applications of this technique that identify a fixed operating point, the models are used to uncover dimensions of filaments obtainable within the operating boundaries of our system. Process-setting predictions are then made through multi-objective optimization of the models. An interesting outcome of this study is the ability to produce filaments of different shrinkage and tensile strength properties by solely changing process settings. As a follow-up, we identify optimal lateral overlap and interlayer spacing parameters to define toolpaths to print structures. If unoptimized, the material’s anisotropic shrinkage and nonlinear compression characteristics cause severe delamination, cross-sectional tapering, and warpage. Finally, we show the linear scalability of the shrinkage model in 3D space, which allows for suitable toolpath compensation to improve the dimensional accuracy of printed artifacts. We believe this first-ever study on the parametrization of the large-scale additive manufacture technique with biocomposites will serve as reference for future sustainable developments in manufacturing.

Additive manufacturing using fine wire-based laser metal deposition

2019 ◽  
Vol 26 (3) ◽  
pp. 473-483
Author(s):  
Muhammad Omar Shaikh ◽  
Ching-Chia Chen ◽  
Hua-Cheng Chiang ◽  
Ji-Rong Chen ◽  
Yi-Chin Chou ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Tensile Strength ◽  
Additive Manufacturing ◽  
High Precision ◽  
Surface Finish ◽  
Dimensional Accuracy ◽  
Laser Metal Deposition ◽  
Cross Sectional ◽  
Content Type ◽  
Fine Wire

Purpose Using wire as feedstock has several advantages for additive manufacturing (AM) of metal components, which include high deposition rates, efficient material use and low material costs. While the feasibility of wire-feed AM has been demonstrated, the accuracy and surface finish of the produced parts is generally lower than those obtained using powder-bed/-feed AM. The purpose of this study was to develop and investigate the feasibility of a fine wire-based laser metal deposition (FW-LMD) process for producing high-precision metal components with improved resolution, dimensional accuracy and surface finish. Design/methodology/approach The proposed FW-LMD AM process uses a fine stainless steel wire with a diameter of 100 µm as the additive material and a pulsed Nd:YAG laser as the heat source. The pulsed laser beam generates a melt pool on the substrate into which the fine wire is fed, and upon moving the X–Y stage, a single-pass weld bead is created during solidification that can be laterally and vertically stacked to create a 3D metal component. Process parameters including laser power, pulse duration and stage speed were optimized for the single-pass weld bead. The effect of lateral overlap was studied to ensure low surface roughness of the first layer onto which subsequent layers can be deposited. Multi-layer deposition was also performed and the resulting cross-sectional morphology, microhardness, phase formation, grain growth and tensile strength have been investigated. Findings An optimized lateral overlap of about 60-70% results in an average surface roughness of 8-16 µm along all printed directions of the X–Y stage. The single-layer thickness and dimensional accuracy of the proposed FW-LMD process was about 40-80 µm and ±30 µm, respectively. A dense cross-sectional morphology was observed for the multilayer stacking without any visible voids, pores or defects present between the layers. X-ray diffraction confirmed a majority austenite phase with small ferrite phase formation that occurs at the junction of the vertically stacked beads, as confirmed by the electron backscatter diffraction (EBSD) analysis. Tensile tests were performed and an ultimate tensile strength of about 700-750 MPa was observed for all samples. Furthermore, multilayer printing of different shapes with improved surface finish and thin-walled and inclined metal structures with a minimum achievable resolution of about 500 µm was presented. Originality/value To the best of the authors’ knowledge, this is the first study to report a directed energy deposition process using a fine metal wire with a diameter of 100 µm and can be a possible solution to improving surface finish and reducing the “stair-stepping” effect that is generally observed for wires with a larger diameter. The AM process proposed in this study can be an attractive alternative for 3D printing of high-precision metal components and can find application for rapid prototyping in a range of industries such as medical and automotive, among others.

scholarly journals Fabricating Pyramidal Lattice Structures of 304 L Stainless Steel by Wire Arc Additive Manufacturing

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3482 ◽  
Author(s):  
Haorui Zhang ◽  
Junjin Huang ◽  
Changmeng Liu ◽  
Yongsheng Ma ◽  
Yafeng Han ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Additive Manufacturing ◽  
Large Scale ◽  
Lattice Structures ◽  
Layer Height ◽  
Superior Mechanical Properties ◽  
Material Utilization ◽  
Wire Arc Additive Manufacturing ◽  
Dendritic Austenite

Lattice structures have drawn considerable attention due to their superior mechanical properties. However, the existing fabrication methods for lattice structures require complex procedures, as they have low material utilization and lead to unreliable node connections, which greatly restricts their application. In this work, wire arc additive manufacturing is used to fabricate large-scale lattice structures efficiently, without any air holes between rods and panels. The principle and the process of fabricating the rods were analyzed systematically. The influence of the two most important parameters, including heat input and preset layer height, is disclosed. Through optical microscopy, the microstructure of the fabricated steel rods is found to consist of dendritic austenite and skeletal ferrite. The tensile strength of the rods can reach 603 MPa, and their elongation reaches 77%. These experimental results demonstrated the feasibility of fabricating lattice structures using wire arc additive manufacturing.

scholarly journals Applicability of finger jointing to circular laminated veneer hollow sections for temporary soil nailing

2020 ◽  
Vol 78 (5) ◽  
pp. 879-889
Author(s):  
Sebastian Hirschmüller ◽  
Roman Marte ◽  
Alexander Englberger
Keyword(s):  
Tensile Strength ◽  
High Performance ◽  
Large Scale ◽  
Beech Wood ◽  
Longitudinal Section ◽  
Tensile Tests ◽  
Strength Properties ◽  
Wood Veneer ◽  
Soil Nail ◽  
Finger Jointing

Abstract This paper investigates the strength properties of circular laminated veneer lumber hollow sections made of beech wood and loaded in tension. These tubular, hollow wooden poles are intended for an innovative geotechnical approach, which utilizes the high tensile strength of beech wood and its limited durability as soil nails for temporary geotechnical slope stabilisation. Due to the standardized design approaches of soil nail walls that prevent a rigid soil body from sliding by using nails as reinforcement elements, primary tension loads will be aligned to the structural elements. Depending on the height of the soil nail wall, nails with a length up to 10 m may be necessary, demanding for high-performance longitudinal section joints due to the natural length limitations of the wood veneer. This paper discusses the applicability of finger jointing to tubular, laminated beech wood veneer poles and presents the results of large-scale tensile tests. Depending on the joint arrangement, the median tensile strength is reduced by 37–43% compared to the unjointed sections of a similar geometry. Thus, finger jointing has been found to be an efficient method of a longitudinal load-carrying connection in combination with a minimized cross section reduction at the joint. However, due to the low sample size of the tests, further improvements are necessary.

A Rapid Manufacturing Process for Extrusion-Based 3D Printers

2019 ◽  
Author(s):  
Andreas Schroeffer ◽  
Matthias Trescher ◽  
Konstantin Struebig ◽  
Yannik Krieger ◽  
Tim C. Lueth
Keyword(s):  
Tensile Strength ◽  
Additive Manufacturing ◽  
Injection Molding ◽  
Manufacturing Process ◽  
Polymer Melt ◽  
Dimensional Accuracy ◽  
Casting Process ◽  
Extrusion Process ◽  
Mechanical Component ◽  
Plastic Parts

Abstract The generation of plastic parts in small volume batches has an enormous economic significance. Application fields for parts in small lot sizes are the fabrication of prototypes in the design process or individualized products. The goal thereby often is not only to produce show objects, but functional parts with specific materials, high dimensional accuracy and proper mechanical properties in a short amount of time. The conventional way to produce thermoplastic plastic parts is given by injection molding and extrusion. Characteristics for this technology are the resulting good and homogeneous mechanical component properties, but shape freedom is limited and the process is time consumptive because an individual tool is needed for each product. Depending on the design of the part the geometry of the tool can be complex and an iterative process is necessary to create a suitable mold. On the other hand, the technology of additive manufacturing is a growing market for the quick and cheap production of parts as prototypes, but still the range of materials is limited and anisotropic mechanical component properties are ongoing problems. The combination of both technologies is known as rapid tooling, where the mold is produced in an additive manufacturing process and then used in an injection molding or casting process. This approach combines the benefits of both technologies in term of time and cost efficiency and good component properties. Problems here are the combination of different materials for mold and component and the missing process knowledge and automatization. In this paper an extrusion-based additive manufacturing technology is used to combine additive manufacturing and injection infill generation for thermoplast in one process. The proposed working principle is to generate the outer contour of the part by filament extrusion as mold to ensure high accuracy and good surface quality and fill the mold using an extrusion process of polymer melt without filament generation. Accordingly, the mold becomes part of the component and the same material can be used for the mold and the infill. Since the viscosity of most thermoplastic polymer melts is too high to fill big structures and undercuts, an algorithm is proposed to generate a chamber structure inside the part. Consequently, the fabrication process consists of several iterative cycles of mold generation and injection processes. For this paper polyamide 6 is used to demonstrate the process. Experiments were performed to find the optimal chamber geometry and size to avoid holes and generate a high quality infill. Several component properties such as density, tensile strength and fabrication time are analyzed. In spite of still existing blowholes, a higher component density could be achieved with the proposed process compared to additive manufacturing. However, the tensile strength is still significantly lower. The failures appeared at the weld lines, where warm polymer melt was injected to already colder chambers below. Still manual processes are sources of possible defects as well. The integration of a RFID chip is shown as an additional feature of the process of easy integration of passive electronic elements.

Increased dryness after pressing and wet web strength by utilizing foam application technology

TAPPI Journal ◽  
2016 ◽  
Vol 15 (11) ◽  
pp. 731-738 ◽  
Author(s):  
KARITA KINNUNEN-RAUDASKOSKI ◽  
KRISTIAN SALMINEN ◽  
JANI LEHMONEN ◽  
TUOMO HJELT
Keyword(s):  
Tensile Strength ◽  
Guar Gum ◽  
Paper Industry ◽  
Reference Sample ◽  
Strength Properties ◽  
Cellulose Microfibrils ◽  
Application Technology ◽  
Ethylene Vinyl Alcohol ◽  
Wet Pressing ◽  
Web Strength

Production cost savings by lowering basis weight has been a trend in papermaking. The strategy has been to decrease the amount of softwood kraft pulp and increase use of fillers and recycled fibers. These changes have a tendency to lower strength properties of both the wet and dry web. To compensate for the strength loss in the paper, a greater quantity of strength additives is often required, either dosed at the wet end or applied to the wet web by spray. In this pilot-scale study, it was shown how strength additives can be effectively applied with foam-based application technology. The technology can simultaneously increase dryness after wet pressing and enhance dry and wet web strength properties. Foam application of polyvinyl alcohol (PVA), ethylene vinyl alcohol (EVOH), carboxymethyl cellulose (CMC), guar gum, starch, and cellulose microfibrils (CMF) increased web dryness after wet pressing up to 5.2%-units compared to the reference sample. The enhanced dewatering with starch, guar gum, and CMF was detected with a bulk increase. Additionally, a significant increase in z-directional tensile strength of dry web and and in-plane tensile strength properties of wet web was obtained. Based on the results, foam application technology can be a very useful technology for several applications in the paper industry.

Large-Scale Cross-Sectional Study of the Problem Areas in Diabetes Survey among Japanese Patients with Type 2 Diabetes Mellitus

Diabetes ◽  
2018 ◽  
Vol 67 (Supplement 1) ◽  
pp. 2393-PUB
Author(s):  
KENICHIRO TAKAHASHI ◽  
MINORI SHINODA ◽  
RIKA SAKAMOTO ◽  
JUN SUZUKI ◽  
TADASHI YAMAKAWA ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Type 2 Diabetes ◽  
Type 2 Diabetes Mellitus ◽  
Large Scale ◽  
Japanese Patients ◽  
Cross Sectional Study ◽  
Sectional Study ◽  
Cross Sectional ◽  
Diabetes Survey

Knowledge and awareness about MERS-CoV among the dental students in Chennai

2020 ◽  
Vol 11 (SPL1) ◽  
pp. 847-851
Author(s):  
Nithyanandham Masilamani ◽  
Dhanraj Ganapathy
Keyword(s):  
College Students ◽  
Large Scale ◽  
Preventive Measures ◽  
Positive Impact ◽  
Educational Programs ◽  
Dental Students ◽  
Professional Organizations ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
Mode Of Transmission

Middle East Respiratory Syndrome (MERS) induced by new ß coronavirus MERS-(CoV) had first been described in Saudi Arabia in September 2012. MERS-CoV communication inside the population is often identified with clustered households and cramped communal spaces. The purpose of the study is to assess the knowledge and awareness of MERS-CoV among dental students in India. This was a questionnaire-based cross-sectional survey of 100 dental college students in Chennai. The self-designed questionnaires contained ten questions focused on the knowledge and awareness of MERS-CoV amongst dental college students. Questionnaires were circulated through an online website survey planet. After the responses were received from 100 participants, data were collected and analyzed, .87% are aware of MERS-CoV through media 13% from professional channels. 84%are aware of the clinical manifestation of MERS-CoV. 81%Are aware of the mode of transmission of MERS-CoV. 76%are aware of the preventive measures against MERS -CoV.68%. Are aware of the incubation period of MERS-CoV. 74%aware of PCR as a diagnostic test for MERS-CoV. This study concluded that dental students had strong awareness and knowledge of MERS. Also, there are a few differences in information and behaviours that require change. Large-scale health educational programs on MERS also should be facilitated by professional organizations to expand their reach and to strengthen knowledge to have a positive impact on their behaviour.

Gambling-like video game practices: A cross-sectional study of links with problem gambling and disordered gaming

2019 ◽  
Author(s):  
David Zendle
Keyword(s):  
Video Games ◽  
Problem Gambling ◽  
Video Game ◽  
Large Scale ◽  
Significant Degree ◽  
Cross Sectional Study ◽  
Video Gaming ◽  
Cross Sectional ◽  
Streaming Services ◽  
Clinically Significant

A variety of practices have recently emerged which are related to both video games and gambling. Most prominent of these are loot boxes. However, a broad range of other activities have recently emerged which are also related to both gambling and video games: esports betting, real-money video gaming, token wagering, social casino play, and watching videos of both loot box opening and gambling on game streaming services like Twitch.Whilst a nascent body of research has established the robust existence of a relationship between loot box spending and both problem gambling and disordered gaming, little research exists which examines whether similar links may exist for the diverse practices outlined above. Furthermore, no research has thus far attempted to estimate the prevalence of these activities.A large-scale survey of a representative sample of UK adults (n=1081) was therefore conducted in order to investigate these issues. Engagement in all measured forms of gambling-like video game practices were significantly associated with both problem gambling and disordered gaming. An aggregate measure of engagement was associated with both these outcomes to a clinically significant degree (r=0.23 and r=0.43). Engagement in gambling-like video game practices appeared widespread, with a 95% confidence interval estimating that 16.3% – 20.9% of the population engaged in these activities at least once in the last year. Engagement in these practices was highly inter-correlated: Individuals who engaged in one practice were likely to engage in several more.Overall, these results suggest that the potential effects of the blurring of lines between video games and gambling should not primarily be understood to be due to the presence of loot boxes in video games. They suggest the existence of a convergent ecosystem of gambling-like video game practices, whose causal relationships with problem gambling and disordered gaming are currently unclear but must urgently be investigated.

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