Additive manufacturing (AM) alias 3D printing translates computer-aided design (CAD) virtual 3D models into physical objects. By digital slicing of CAD, 3D scan, or tomography data, AM builds objects layer by layer without the need for molds or machining. AM enables decentralized fabrication of customized objects on demand by exploiting digital information storage and retrieval via the Internet. The ongoing transition from rapid prototyping to rapid manufacturing prompts new challenges for mechanical engineers and materials scientists alike. Because polymers are by far the most utilized class of materials for AM, this Review focuses on polymer processing and the development of polymers and advanced polymer systems specifically for AM. AM techniques covered include vat photopolymerization (stereolithography), powder bed fusion (SLS), material and binder jetting (inkjet and aerosol 3D printing), sheet lamination (LOM), extrusion (FDM, 3D dispensing, 3D fiber deposition, and 3D plotting), and 3D bioprinting....

Polymers for 3D Printing and Customized Additive Manufacturing

The use of 3D printing for rapid tooling and manufacturing has promised to produce components with complex geometries according to computer designs. Due to the intrinsically limited mechanical properties and functionalities of printed pure polymer parts, there is a critical need to develop printable polymer composites with high performance. 3D printing offers many advantages in the fabrication of composites, including high precision, cost effective and customized geometry. This article gives an overview on 3D printing techniques of polymer composite materials and the properties and performance of 3D printed composite parts as well as their potential applications in the fields of biomedical, electronics and aerospace engineering. Common 3D printing techniques such as fused deposition modeling, selective laser sintering, inkjet 3D printing, stereolithography, and 3D plotting are introduced. The formation methodology and the performance of particle-, fiber- and nanomaterial-reinforced polymer composites are emphasized. Finally, important limitations are identified to motivate the future research of 3D printing.

3D printing of polymer matrix composites: A review and prospective

Additive manufacturing (AM) is poised to bring about a revolution in the way products are designed, manufactured, and distributed to end users. This technology has gained significant academic as well as industry interest due to its ability to create complex geometries with customizable material properties. AM has also inspired the development of the maker movement by democratizing design and manufacturing. Due to the rapid proliferation of a wide variety of technologies associated with AM, there is a lack of a comprehensive set of design principles, manufacturing guidelines, and standardization of best practices. These challenges are compounded by the fact that advancements in multiple technologies (for example materials processing, topology optimization) generate a "positive feedback loop" effect in advancing AM. In order to advance research interest and investment in AM technologies, some fundamental questions and trends about the dependencies existing in these avenues need highlighting. The goal of our review paper is to organize this body of knowledge surrounding AM, and present current barriers, findings, and future trends significantly to the researchers. We also discuss fundamental attributes of AM processes, evolution of the AM industry, and the affordances enabled by the emergence of AM in a variety of areas such as geometry processing, material design, and education. We conclude our paper by pointing out future directions such as the "print-it-all" paradigm, that have the potential to re-imagine current research and spawn completely new avenues for exploration. The fundamental attributes and challenges/barriers of Additive Manufacturing (AM).The evolution of research on AM with a focus on engineering capabilities.The affordances enabled by AM such as geometry, material and tools design.The developments in industry, intellectual property, and education-related aspects.The important future trends of AM technologies.

The status, challenges, and future of additive manufacturing in engineering

Additive manufacturing (AM) technology has been researched and developed for more than 20 years. Rather than removing materials, AM processes make three-dimensional parts directly from CAD models by adding materials layer by layer, offering the beneficial ability to build parts with geometric and material complexities that could not be produced by subtractive manufacturing processes. Through intensive research over the past two decades, significant progress has been made in the development and commercialization of new and innovative AM processes, as well as numerous practical applications in aerospace, automotive, biomedical, energy and other fields. This paper reviews the main processes, materials and applications of the current AM technology and presents future research needs for this technology.

Additive manufacturing: technology, applications and research needs

Along with extensive research on the three-dimensional (3D) printing of polymers and metals, 3D printing of ceramics is now the latest trend to come under the spotlight. The ability to fabricate ceramic components of arbitrarily complex shapes has been extremely challenging without 3D printing. This review focuses on the latest advances in the 3D printing of ceramics and presents the historical origins and evolution of each related technique. The main technical aspects, including feedstock properties, process control, post-treatments and energy source–material interactions, are also discussed. The technical challenges and advice about how to address these are presented. Comparisons are made between the techniques to facilitate the selection of the best ones in practical use. In addition, representative applications of the 3D printing of various types of ceramics are surveyed. Future directions are pointed out on the advancement on materials and forming mechanism for the fabrication of high-performance ceramic components.

3D printing of ceramics: A review

Rapid Prototyping (RP) technologies provide the ability to fabricate initial prototypes from various model materials. Stratasys Fused Deposition Modeling (FDM) is a typical RP process that can fabricate prototypes out of ABS plastic. To predict the mechanical behavior of FDM parts, it is critical to understand the material properties of the raw FDM process material, and the effect that FDM build parameters have on anisotropic material properties. This paper characterizes the properties of ABS parts fabricated by the FDM 1650. Using a Design of Experiment (DOE) approach, the process parameters of FDM, such as raster orientation, air gap, bead width, color, and model temperature were examined. Tensile strengths and compressive strengths of directionally fabricated specimens were measured and compared with injection molded FDM ABS P400 material. For the FDM parts made with a 0.003 inch overlap between roads, the typical tensile strength ranged between 65 and 72 percent of the strength of injection molded ABS P400. The compressive strength ranged from 80 to 90 percent of the injection molded FDM ABS. Several build rules for designing FDM parts were formulated based on experimental results.

Anisotropic material properties of fused deposition modeling ABS

Objective: The aim of this study was to determine how head and neck postures vary when using two media tablet (slate) computers in four common user configurations. Methods: Fifteen experienced media tablet users completed a set of simulated tasks with two media tablets in four typical user configurations. The four configurations were: on the lap and held with the user's hands, on the lap and in a case, on a table and in a case, and on a table and in a case set at a high angle for watching movies. An infra-red LED marker based motion analysis system measured head/neck postures. Results: Head and neck flexion significantly varied across the four configurations and across the two tablets tested. Head and neck flexion angles during tablet use were greater, in general, than angles previously reported for desktop and notebook computing. Postural differences between tablets were driven by case designs, which provided significantly different tilt angles, while postural differences between configurations were driven by gaze and viewing angles. Conclusion: Head and neck posture during tablet computing can be improved by placing the tablet higher to avoid low gaze angles (i.e. on a table rather than on the lap) and through the use of a case that provides optimal viewing angles.

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Touch-screen tablet user configurations and case-supported tilt affect head and neck flexion angles.

Rapid Prototyping (RP) technology has been advanced to fabricate initial prototypes from various materials. Stratasys’ Fused Deposition Modeling (FDM) is one of the typical RP processes that provide functional prototypes of ABS plastic. In order to predict the behavior of final ABS parts, it is critical to understand the material properties of the raw FDM process material, and the effect that FDM build parameters have on composite material properties. In this paper, we seek t the properties of ABS parts fabricated by the FDM 1650. Using the Design of Experiment (DOE) approach, the process parameters of FDM, such as raster orientation, air gap, bead width, color, and model temperature were examined. Tensile strengths of crisscross specimens, [45 °/-45°], cross specimens, [0 °/90°], and directionally fabricated tensile specimens ([0°] and [90 °]) were measured and compared with the injection molded FDMABS P400 material. For the FDM parts made with a –0.003” air gap, the typical tensile strength ranged between 65 percent and 72 percent of the strength of injection molded ABS P400. From the experiment s, several build rules for designing FDM parts were obtained.

/pdf/material-characterization-of-fused-deposition-modeling-fdm-2dev0p3u04.pdf

Material Characterization of Fused Deposition Modeling (FDM) ABS by Designed Experiments

BACKGROUND: Due to its rapid growth in popularity, there is an imminent need for ergonomic evaluation of the touch-screen tablet computing form-factor. OBJECTIVE: The aim of this study was to assess postures of the shoulders and wrists and their associated muscle activity during touch-screen tablet use. METHODS: Fifteen experienced adult tablet users completed a set of simulated software tasks on two media tablets in a total of seven user configurations. Configurations consisted of a combination of a support condition (held with one hand, two hands or in a case), a location (on the lap or table surface), and a software task (web browsing, email, and game). Shoulder postures were measured by using an infra-red LED marker based motion analysis system, wrist postures by electro-goniometry, and shoulder (upper trapezius and anterior deltoid) and forearm (flexor carpi radialis, flexor carp ulnaris, and extensor radialis) muscle activity by surface electromyography. RESULTS: Postures and muscle activity for the wrist significantly varied across configurations and between hands, but not across the two tablets tested. Wrist extension was high for all configurations and particularly for the dominant hand when a tablet was placed on the lap (mean = 38 ◦ ). Software tasks involving the virtual keyboard (e-mailing) corresponded to higher wrist extensor muscle activity (50 th percentile = 9.5% MVC) and wrist flexion/extension acceleration (mean = 322 ◦ /s 2 ). High levels of wrist radial deviation were observed for the non-dominant hand when it was used to tilt and hold the tablet (mean = 13 ◦ ). Observed differences in posture and muscle activity of the shoulder were driven by tablet location. CONCLUSION: Touch-screen tablet users are exposed to extreme wrist postures that are less neutral than other computing technologies and may be at greater risk of developing musculoskeletal symptoms. Tablets should be placed in cases or stands that adjust the tilt of the screen rather than supporting and tilting the tablet with only one hand.

Wrist and shoulder posture and muscle activity during touch-screen tablet use: Effects of usage configuration, tablet type, and interacting hand

This study quantified postures of users working on a notebook computer situated in their lap and tested the effect of using a device designed to increase the height of the notebook when placed on the lap. A motion analysis system measured head, neck and upper extremity postures of 15 adults as they worked on a notebook computer placed on a desk (DESK), the lap (LAP) and a commercially available lapdesk (LAPDESK). Compared with the DESK, the LAP increased downwards head tilt 6 degrees and wrist extension 8 degrees . Shoulder flexion and ulnar deviation decreased 13 degrees and 9 degrees , respectively. Compared with the LAP, the LAPDESK decreased downwards head tilt 4 degrees , neck flexion 2 degrees , and wrist extension 9 degrees. Users reported less discomfort and difficulty in the DESK configuration. Use of the lapdesk improved postures compared with the lap; however, all configurations resulted in high values of wrist extension, wrist deviation and downwards head tilt. STATEMENT OF RELEVANCE: This study quantifies postures of users working with a notebook computer in typical portable configurations. A better understanding of the postures assumed during notebook computer use can improve usage guidelines to reduce the risk of musculoskeletal injuries.

Dan Odell

Papers

Anisotropic material properties of fused deposition modeling ABS

Touch-screen tablet user configurations and case-supported tilt affect head and neck flexion angles.

Material Characterization of Fused Deposition Modeling (FDM) ABS by Designed Experiments

Wrist and shoulder posture and muscle activity during touch-screen tablet use: Effects of usage configuration, tablet type, and interacting hand

Notebook computer use on a desk, lap and lap support: Effects on posture, performance and comfort