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

Additive manufacturing: scientific and technological challenges, market uptake and opportunities

Three-dimensional (3D) printing has numerous applications and has gained much interest in the medical world. The constantly improving quality of 3D-printing applications has contributed to their increased use on patients. This paper summarizes the literature on surgical 3D-printing applications used on patients, with a focus on reported clinical and economic outcomes. Three major literature databases were screened for case series (more than three cases described in the same study) and trials of surgical applications of 3D printing in humans. 227 surgical papers were analyzed and summarized using an evidence table. The papers described the use of 3D printing for surgical guides, anatomical models, and custom implants. 3D printing is used in multiple surgical domains, such as orthopedics, maxillofacial surgery, cranial surgery, and spinal surgery. In general, the advantages of 3D-printed parts are said to include reduced surgical time, improved medical outcome, and decreased radiation exposure. The costs of printing and additional scans generally increase the overall cost of the procedure. 3D printing is well integrated in surgical practice and research. Applications vary from anatomical models mainly intended for surgical planning to surgical guides and implants. Our research suggests that there are several advantages to 3D-printed applications, but that further research is needed to determine whether the increased intervention costs can be balanced with the observable advantages of this new technology. There is a need for a formal cost–effectiveness analysis.

/pdf/3d-printing-techniques-in-a-medical-setting-a-systematic-53jv953e7s.pdf

3D-printing techniques in a medical setting: a systematic literature review

Additive manufacturing (AM) is a technology which has the potential not only to change the way of conventional industrial manufacturing processes, adding material instead of subtracting, but also to create entirely new production and business strategies. Since about three decades, AM technologies have been used to fabricate prototypes or models mostly from polymeric or metallic materials. Recently, products have been introduced into the market that cannot be produced in another way than additively. Ceramic materials are, however, not easy to process by AM technologies, as their processing requirements (in terms of feedstock and/or sintering) are very challenging. On the other hand, it can be expected that AM technologies, once successful, will have an extraordinary impact on the industrial production of ceramic components and, moreover, will open for ceramics new uses and new markets.

Additive Manufacturing of Ceramics: Issues, Potentialities, and Opportunities

A cost-effective method of complex ceramic parts manufacturing using stereolithography has been developed. The process consists in fabricating ceramic pieces by laser polymerization of an UV curable monomeric system, subsequent removal of organic components and sintering. Highly concentrated suspensions of well dispersed ceramic particles (up to 60 vol%) in a reactive acrylic monomer, with a suitable rheological behaviour for the spreading of thin layers (down to 25 μm) were defined. Adequate cured depth (higher than 200 μm) is obtained even at high scanning speeds. Nevertheless, a compromise has to be found between the cured depth and the cured width to improve the dimensional resolution. The dimensional resolution reached on alumina partterns is about 200 μm with an energy density of 0.05 J · cm−2.

Stereolithography of structural complex ceramic parts

Among the different rapid prototyping technologies, solid freeform fabrication (SFF) is the most suitable for ceramics. Here a stereolithographic technique is presented that allows the usage of pastes composed of ceramic particles dispersed in a photocurable resin for the fabrication of alumina pieces. They exhibit a similar flexural strength than alumina parts made by classical techniques like pressing.

Stereolithography for manufacturing ceramic parts

Introduction Neurosurgery and Maxillofacial Surgery Departments of Limoges University Hospital Centre have developed a new concept of a custom made ceramic implant in hydroxyapatite (HA) for the reconstruction of large and complex craniofacial bone defects (more than 25 cm 2 ). Materials and methods The manufacturing process of the implants used a stereolithography technique that produces implants with three-dimensional shapes derived directly from the scan file of the patient's skull without moulding or machining. Eight patients received 8 implants between 2005 and 2008. Results The surgical procedure is simple and fast. The post-operative follow-up was 12 months. No major complications (infection or fracture of the implant) were observed. The cosmetic result was considered satisfactory by both patients and surgeons. Conclusions These new implants are well suited for reconstruction of large craniofacial bone defects (greater than 25 cm 2 ) in adults and children over 8 years.

A new custom made bioceramic implant for the repair of large and complex craniofacial bone defects.

The multiple light scattering in concentrated alumina suspensions adapted to stereolithography can be modeled using diffuse reflectance measurements coupled to the Kubelka-Munk model. The penetration depth of UV radiation can be related to the scattering coefficient allowing the prediction of the cure depth with an accuracy of 20%.

Optical characterization of stereolithography alumina suspensions using the Kubelka-Munk model

Complex ceramic parts, designed by 3D electromagnetic simulations for microwave devices of high performances, are difficult, even impossible, to elaborate by classical ceramic processing routes. This paper demonstrates the direct fabrication of useful complex microwave devices in millimeter and submillimeter wavelength domains, with a high dimensional resolution, by the numerical techniques of stereolithography and microstereolithography. Alumina and zirconia formulations have been developed with a powder loading 450 vol%, a suitable rheology to spread thin (25-50 lm) and homogeneous layers, and with a sufficient reactivity to UV for polymerization. Devices built with a satisfying manufacturing accuracy have presented excellent experimental electrical behaviors in good agreement with the theoretical ones.

Christophe Chaput

Papers

Stereolithography of structural complex ceramic parts

Stereolithography for manufacturing ceramic parts

A new custom made bioceramic implant for the repair of large and complex craniofacial bone defects.

Optical characterization of stereolithography alumina suspensions using the Kubelka-Munk model

Fabrication of Millimeter Wave Components Via Ceramic Stereo- and Microstereolithography Processes