Manufacturing methods for medical artificial prostheses– a review
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paper_title: Asymmetric Single Point Incremental Forming of Sheet Metal

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The use of computers in manufacturing has enabled the development of several new sheet metal forming processes, which are based upon older technologies. This paper describes modifications that have been made to traditional forming methods such as conventional spinning and shear forming, forming processes in which deformation is localized. Recent advances have enabled this localized deformation to be accurately controlled and studied. Current developments have been focused on forming asymmetric parts using CNC technology, without the need for costly dies. Asymmetric Incremental Sheet Forming has the potential to revolutionize sheet metal forming, making it accessible to all levels of manufacturing. This paper describes the genesis and current state-of-the-art of Asymmetric Incremental Sheet Forming.
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paper_title: Incremental Forming with Local Heating by Laser Irradiation for Magnesium Alloy Sheet

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Abstract An incremental sheet forming system with dynamic local heating by laser irradiation was developed to form magnesium alloy sheet which is typical lightweight hard-to-form sheet metal. In this process, tool contact area of a blank sheet is locally heated by a moving laser beam spot to increase the material ductility and decrease the material strength dynamically and partially. Incremental forming experiments of AZ31 magnesium alloy sheet was carried out under several laser irradiation conditions and forming speeds using the developed forming system. The experimental results show that the formability of AZ31 sheets increased remarkably with increasing laser power. Defocusing distance of laser beam and forming speed also affected the formability. The results also indicate that residual stress of the formed product was markedly reduced to almost zero by local heating.
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paper_title: Application of Incremental Forming process for high customised medical product manufacturing

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Abstract Incremental Forming processes have been introduced in the recent past as an alternative to the money consuming stamping technology, when small batches have to be manufactured. Anyway, they introduce some advantages in terms of flexibility and material formability but, also, some problems such as the dimensional accuracy decreasing. In this paper, a particular application is carried out taking into account the development of an innovative technique to produce a customised ankle support. In this way Incremental Forming process has been selected for the sheet profiling, exalting the role that this technology may play when single complex product has to be manufactured. The producing procedure finishes with a measure of the dimensional accuracy that shown a good result for the desired application.
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paper_title: Experimental investigations on hardness of the biomedical implants prepared by hybrid investment casting

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Abstract In this paper for total hip replacement, a systematic procedure for development of primary (1°) implants of stainless steel has been outlined with fused deposition modeling (FDM) assisted hybrid investment casting process. As the suitability of the implant is mainly assessed by in vitro analysis, the change in microstructure and surface hardness is one of the important parameter/criterion for estimating the functional ability of 1° implants. In order to achieve the increased hardness and improved microstructure of the implants, process parameters of FDM and investment casting process have been identified and optimized in this research work. The analysis of variance has been used to find the percentage contribution of each factor. It has been observed that mold thickness and volume to surface area ratio of the casting plays a significant role in deciding the microstructure and hardness of the castings. Therefore, by controlling these parameters the required microstructure and hardness can be achieved for 1° implants. This study may be used as a yardstick for deciding the levels of coating as secondary (2°) implants (if required) for in vitro and in vivo analysis.
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paper_title: Production of customized hip stem prostheses – a comparison between conventional machining and electron beam melting (EBM)

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Purpose - The purpose of this paper is to study the use of the additive manufacturing (AM) method, electron beam melting (EBM), for manufacturing of customized hip stems. The aim is to investigate ...
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paper_title: Dimensional accuracy and surface finish of biomedical implant fabricated as rapid investment casting for small to medium quantity production

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Abstract In this work the feasibility of combined route of fused deposition modelling (FDM), chemical vapor smoothing (CVS), vacuum casting (VC) and investment Casting (IC) for the development of customized implant for small to medium quantity production has been investigated. Further, an effort has been made to optimize the dimensional accuracy and surface finish of the implant (hip joint) prepared by varying two controllable factors (namely: drying time of primary coating and mould thickness) each at three levels of the IC process. The master pattern of the hip joint has been prepared by FDM followed by the CVS process to enhance the surface finish and multiple replicas were produced by the VC process for batch production. The tolerance grades for the selected dimension of the implant/castings were found to be acceptable as per the ISO standard UNI EN 20286-I (1995). Also, the Cpk value greater than 1.3 indicated that the proposed process is statistically controlled.
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paper_title: Development of Biomedical Implant (Hip Joint) by Combining Fused Deposition Modelling and Investment Casting

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This research work is aimed at the development of biomedical implant (hip joint) by combination of fused deposition modelling (FDM) and investment casting. Three controllable factors of the investment casting process (namely slurry layer combination, viscosity, dry time of primary coating) were studied at three levels each by Taguchi’s parametric approach, and single-response optimization was conducted to identify the main factors controlling dimensional accuracy (Δd). ABS patterns to be used for investment casting were made with FDM process, and castings were produced using stainless steel at recommended parameters through ceramic shell investment casting process. The results of the study suggest that for Δd, contribution of viscosity of primary dip and dry time of primary coating is 23 and 72 %, respectively.
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paper_title: Developments in investment casting process—A review

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Abstract Investment casting has been used to manufacture weapons, jewellery and art castings during the ancient civilization. Today, its applications include jewellery/art castings, turbine blades and many more industrial/scientific components. The present paper reviews various investigations made by researchers in different stages of investment casting and highlights their importance. The paper initially highlights the investigations made on pattern wax properties, effects of blending, additives and fillers. Different ways through which pattern properties (like surface finish, dimensional accuracy, etc.) could be enhanced by properly controlling the injection processing parameters are thoroughly discussed. The paper also looks into the investigations made to enhance the strength, surface finish, etc. of ceramic shell for ferrous alloys/non-ferrous alloys as well as superalloys in investment casting. Investigations made on incorporation of nylon fibers and polymer additions confirm that a ceramic shell reinforced with nylon fibers attains additional permeability compared to the one with polymer additions. Different investigations carried out on autoclave dewaxing and microwave dewaxing conclude that the wax properties are less altered with microwave dewaxing when compared to an autoclave dewaxing. Some recent investigations carried out on pouring and post-treatment operations are also discussed in the paper. The advent and emergence of rapid prototyping in investment casting are broadly exposed in the subsequent sections of the paper. Various aspects of rapid prototyping like rapid investment casting, rapid freeze prototyping, etc., along with their advantages are projected. The emerging areas of applications of rapid prototyping like dentistry, etc., are duly discussed.
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paper_title: Titanium based cranial reconstruction using incremental sheet forming

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In this paper, we report recent work in cranial plate manufacturing using incremental sheet forming (ISF) process. With a typical cranial shape, the ISF process was used to manufacture the titanium cranial shape by using different ISF tooling solutions with and without backing plates. Detailed evaluation of the ISF process including material deformation and thinning, geometric accuracy and surface finish was conducted by using a combination of experimental testing and Finite Element (FE) simulation. The results show that satisfactory cranial shape can be achieved with sufficient accuracy and surface finish by using a feature based tool path generation method and new ISF tooling design. The results also demonstrate that the ISF based cranial reconstruction has the potential to achieve considerable lead time reduction as compared to conventional methods for cranial plate manufacturing. This outcome indicates that there is a potential for the ISF process to achieve technological advances and economic benefits as well as improvement to quality of life.
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paper_title: Review on the influence of process parameters in incremental sheet forming

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Incremental sheet forming (ISF) is a relatively new flexible forming process. ISF has excellent adaptability to conventional milling machines and requires minimum use of complex tooling, dies and forming press, which makes the process cost-effective and easy to automate for various applications. In the past two decades, extensive research on ISF has resulted in significant advances being made in fundamental understanding and development of new processing and tooling solutions. However, ISF has yet to be fully implemented to mainstream high-value manufacturing industries due to a number of technical challenges, all of which are directly related to ISF process parameters. This paper aims to provide a detailed review of the current state-of-the-art of ISF processes in terms of its technological capabilities and specific limitations with discussions on the ISF process parameters and their effects on ISF processes. Particular attention is given to the ISF process parameters on the formability, deformation and failure mechanics, springback and accuracy and surface roughness. This leads to a number of recommendations that are considered essential for future research effort.
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paper_title: Medical Applications for 3D Printing: Current and Projected Uses

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Medical applications for 3D printing are expanding rapidly and are expected to revolutionize health care.1 Medical uses for 3D printing, both actual and potential, can be organized into several broad categories, including: tissue and organ fabrication; creation of customized prosthetics, implants, and anatomical models; and pharmaceutical research regarding drug dosage forms, delivery, and discovery.2 The application of 3D printing in medicine can provide many benefits, including: the customization and personalization of medical products, drugs, and equipment; cost-effectiveness; increased productivity; the democratization of design and manufacturing; and enhanced collaboration.1,3–6 However, it should be cautioned that despite recent significant and exciting medical advances involving 3D printing, notable scientific and regulatory challenges remain and the most transformative applications for this technology will need time to evolve.3–5,7
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paper_title: Fabrication of micro open structure using 3D laser scanning method in nano-stereolithography

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As interest in fabrication methods for three dimensional (3D) structures has increased, various studies have been conducted to fabricate micro- and nano-structures. The nano-stereolithography process has been recognized as one of the most promising technologies for the fabrication of three-dimensional micro structures with submicron fabrication resolution, and to meet the demand for a process of fabrication of complex 3D micro structures. By considering the surface tension during the fabrication process, it is possible to increase both the fabrication efficiency and the success rate. In this paper, an open structure was fabricated using the 3D laser scanning method. For the fabrication of a perfectly supported open structure, the line width, according to various levels of laser power, was estimated experimentally and the fabrication window was derived with a number of experiments. Compared to the closed structure, the open structure has advantages in terms of fabrication and its functional perspective.
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paper_title: A Review of Additive Manufacturing

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Additive manufacturing processes take the information from a computer-aided design (CAD) file that is later converted to a stereolithography (STL) file. In this process, the drawing made in the CAD software is approximated by triangles and sliced containing the information of each layer that is going to be printed. There is a discussion of the relevant additive manufacturing processes and their applications. The aerospace industry employs them because of the possibility of manufacturing lighter structures to reduce weight. Additive manufacturing is transforming the practice of medicine and making work easier for architects. In 2004, the Society of Manufacturing Engineers did a classification of the various technologies and there are at least four additional significant technologies in 2012. Studies are reviewed which were about the strength of products made in additive manufacturing processes. However, there is still a lot of work and research to be accomplished before additive manufacturing technologies become standard in the manufacturing industry because not every commonly used manufacturing material can be handled. The accuracy needs improvement to eliminate the necessity of a finishing process. The continuous and increasing growth experienced since the early days and the successful results up to the present time allow for optimism that additive manufacturing has a significant place in the future of manufacturing.
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paper_title: A review on stereolithography and its applications in biomedical engineering

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Stereolithography is a solid freeform technique (SFF) that was introduced in the late 1980s. Although many other techniques have been developed since then, stereolithography remains one of the most powerful and versatile of all SFF techniques. It has the highest fabrication accuracy and an increasing number of materials that can be processed is becoming available. In this paper we discuss the characteristic features of the stereolithography technique and compare it to other SFF techniques. The biomedical applications of stereolithography are reviewed, as well as the biodegradable resin materials that have been developed for use with stereolithography. Finally, an overview of the application of stereolithography in preparing porous structures for tissue engineering is given.
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paper_title: Manufacturability Analysis of Flatness Tolerances in Solid Freeform Fabrication

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Increasingly, Solid Freeform Fabrication (SFF) processes are being considered for creating functional parts. In such applications, SFF can either be used for creating tooling (i.e., patterns for casting, low volume molds, etc.) or directly creating the functional part itself. In order to create defect free functional parts, it is extremely important to fabricate the parts within allowable dimensional and geometric tolerances. This paper describes a systematic approach to analyzing manufacturability of parts produced using SFF processes with flatness tolerance requirements on the planar faces of the part. Our research is expected to help SFF designers and process providers in the following ways. By evaluating design tolerances against a given process capability, it will help designers in eliminating manufacturing problems and selecting the right SFF process for the given design. It will help process providers in selecting a build direction that can meet all design tolerance requirements. @DOI: 10.1115/1.1326439#
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paper_title: 3D printing with polymers: Challenges among expanding options and opportunities

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OBJECTIVES ::: Additive manufacturing, which is more colloquially referred to as 3D printing, is quickly approaching mainstream adoption as a highly flexible processing technique that can be applied to plastic, metal, ceramic, concrete and other building materials. However, taking advantage of the tremendous versatility associated with in situ photopolymerization as well as the ability to select from a variety of preformed processible polymers, 3D printing predominantly targets the production of polymeric parts and models. The goal of this review is to connect the various additive manufacturing techniques with the monomeric and polymeric materials they use while highlighting emerging material-based developments. ::: ::: ::: METHODS ::: Modern additive manufacturing technology was introduced approximately three decades ago but this review compiles recent peer-reviewed literature reports to demonstrate the evolution underway with respect to the various building techniques that differ significantly in approach as well as the new variations in polymer-based materials being employed. ::: ::: ::: RESULTS ::: Recent growth of 3D printing has been dramatic and the ability of the various platform technologies to expand from rapid production prototypic models to the greater volume of readily customizable production of working parts is critical for continued high growth rates. This transition to working part production is highly dependent on adapting materials that deliver not only the requisite design accuracy but also the physical and mechanical properties necessary for the application. ::: ::: ::: SIGNIFICANCE ::: With the weighty distinction of being called the next industrial revolution, 3D printing technologies is already altering many industrial and academic operations including changing models for future healthcare delivery in medicine and dentistry.
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paper_title: Rapid prototyping of temporal bone for surgical training and medical education

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Objective The skills of ear surgery are best developed by dissecting a temporal bone. However, only a limited number of trainees can be afforded this opportunity because of the scarcity of available bones. The aim of this study was to investigate the validity of a prototype temporal bone model for surgical training and education. Material and Methods A simulated 3D model of a human temporal bone was made using a selective laser sintering method. The powder layers were laser-fused based on detailed CT data and accumulated to create a 3D structure. Conventional surgical instruments were used to dissect the model under a microscope. Results The model was as hard as real bone and surface structures were accurately reproduced. The model could be shaved using a surgical drill, burr and suction irrigator in the same way as a real bone. The malleus and incus were reproduced. The semicircular canals and the oval and round window niches were identified. Cavity structures, such as the semicircular canal, vestibule, ...
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paper_title: Error analysis of FDM fabricated medical replicas

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Purpose – Recent advancement in fused deposition modelling (FDM) rapid prototyping technology has made it a viable technology for application in reconstructive surgery. The purpose of this paper is to investigate the errors generated during the fabrication stage of complex anatomical replicas derived from computed tomography coupled with the technique of FDM.Design/methodology/approach – An evaluation on the errors generated during the fabrication process of two anatomical parts (skull or mandible) for different human sizes (infant, female or male) is carried out. A comparison between the linear measurements of 11 landmarks on the virtual model of a skull and nine for the mandible of patient specific and its replica is conducted. Furthermore, eight landmarks are chosen to evaluate the bone thickness variation over the fabricated replicas.Findings – Although the FDM technology proved the ability to manufacture and to fit prosthesis to a patient's unique proportions quickly and with relatively low cost, the...
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paper_title: Prospective study on cranioplasty with individual carbon fiber reinforced polymere (CFRP) implants produced by means of stereolithography

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Abstract Background The aim of this study was to evaluate the value of carbon fiber reinforced polymere (CFRP) cranial implants produced by means of 3-dimentional (3D) stereolithography (SL) and template modeling for reconstructions of complex or extensive cranial defects. Patients A series of 41 cranioplasties with individual CFRP implants was performed in 37 patients between April 1996 and November 2002. Only patients with complex and/or large cranial defects were included, most of them having extended scarring or dural calcification and poor quality of the overlying soft-tissue cover after infection or multiple preceding operations. Involvement of frontal sinus, a known risk factor for complications after cranioplasty, was the case in 21 patients (51.2%). Methods A computer-based 3D model of the skull with the bony defect was generated by means of stereolithography after acquisition, evaluation and transfer of the patient's helical computed tomography (CT) data. A wax template of the defect that was used to design the individual prosthesis-shape was invested in dental stone. Then, the cranial implant was fabricated out of CFRP by loosen mold. Results Reconstruction of defects measuring up to 17 × 9 cm was performed. The intra-operative fit of the implants was excellent in 36 (87.8%), good in 1 (2.4%), and fair in 4 (9.8%) of the cases. Problems of implant fit occurred because of extended scarring and poor quality of soft-tissue cover. Adverse reactions were observed in 5 patients (1 subdural, 1 subcutaneous hematoma, 2 infections, 1 allergic reaction). Excellent contours and a solid stable reconstruction have been maintained in 30 out of 35 remaining plates (mean follow-up 3.6 years). No adverse effects concerning postoperative imaging, the accuracy of electroencephalograms and radiation therapy have been observed. Conclusions The authors believe that this relatively new technique represents an advance in the management of complex and large cranial defects, but seems less suitable for simple defects because of cost-intensive techniques. Because of the high mechanical strength, biocompatibility, innovative design, and especially radiolucency, CFRP implants should, however, be considered in smaller defects if further imaging investigations or irradiation therapies are necessary.
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paper_title: A volumetric approach for STL generation from 3D scanned products

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Reverse engineering and rapid prototyping are competitive tools for quick distributed product design and enhancement. The possibility to send data over the Internet for the reproduction of physical prototypes in different geographic locations is very attractive, especially in the context of globalization and distributed manufacturing. Currently, the most immediate link between these technologies is the solid to layer (STL) tessellation file that has become one of the industrial standard exchange formats. As a consequence the creation of robust STL files is a crucial task both for direct rapid prototyping purposes and data exchange purposes. Several methodologies have been developed to perform mesh construction, starting from point clouds. In this paper, an efficient volumetric method based on voxelization is presented and validated with several case studies.
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paper_title: A Novel Low-Cost Stereolithography Process Based on Vector Scanning and Mask Projection for High-Accuracy, High-Speed, High-Throughput, and Large-Area Fabrication

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Photopolymerization based process is one of the most popular additive manufacturing processes. Two primary configurations for this process are laser based vector by vector scanning (0D) and projection based layer by layer exposing (2D). With the highly focused fine laser, the scanning based process can accomplish very high surface finishing and precision, however, due to the serial nature of scanning, this process suffers from the problem of slow speed. In contrast with laser scanning, projection based process can form the whole layer in one exposure, which leads to higher fabrication efficiency. However, due to the limited resolution of projection device and various optical defects, the surface quality will be significantly deteriorated for large area fabrication. To solve this problem, a novel hybrid process by integrating vector scanning and mask projection has been presented. In this process, laser is focused into a fine spot and used to scan the boundary of the layer, whereas the projector is focused onto a large platform surface and used to form the interior area of the layer. An efficient slicing method is proposed for extracting the contour for laser scanning. A slice to image conversion algorithm is also developed to convert the offset contour to grayscale image for mask projection. Experimental results have verified that the proposed hybrid process can significantly improve the fabrication speed without losing the surface quality.Copyright © 2014 by ASME
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paper_title: Fused deposition modeling with polypropylene

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Abstract This paper addresses the potential of polypropylene (PP) as a candidate for fused deposition modeling (FDM)-based 3D printing technique. The entire filament production chain is evaluated, starting with the PP pellets, filament production by extrusion and test samples printing. This strategy enables a true comparison between parts printed with parts manufactured by compression molding, using the same grade of raw material. Printed samples were mechanically characterized and the influence of filament orientation, layer thickness, infill degree and material was assessed. Regarding the latter, two grades of PP were evaluated: a glass-fiber reinforced and a neat, non-reinforced, one. The results showed the potential of the FDM to compete with conventional techniques, especially for the production of small series of parts/components; also, it was showed that this technique allows the production of parts with adequate mechanical performance and, therefore, does not need to be restricted to the production of mockups and prototypes.
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paper_title: Continuous liquid interface production of 3D objects

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Additive manufacturing processes such as 3D printing use time-consuming, stepwise layer-by-layer approaches to object fabrication. We demonstrate the continuous generation of monolithic polymeric parts up to tens of centimeters in size with feature resolution below 100 micrometers. Continuous liquid interface production is achieved with an oxygen-permeable window below the ultraviolet image projection plane, which creates a “dead zone” (persistent liquid interface) where photopolymerization is inhibited between the window and the polymerizing part. We delineate critical control parameters and show that complex solid parts can be drawn out of the resin at rates of hundreds of millimeters per hour. These print speeds allow parts to be produced in minutes instead of hours.
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paper_title: Layerless fabrication with continuous liquid interface production

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Despite the increasing popularity of 3D printing, also known as additive manufacturing (AM), the technique has not developed beyond the realm of rapid prototyping. This confinement of the field can be attributed to the inherent flaws of layer-by-layer printing and, in particular, anisotropic mechanical properties that depend on print direction, visible by the staircasing surface finish effect. Continuous liquid interface production (CLIP) is an alternative approach to AM that capitalizes on the fundamental principle of oxygen-inhibited photopolymerization to generate a continual liquid interface of uncured resin between the growing part and the exposure window. This interface eliminates the necessity of an iterative layer-by-layer process, allowing for continuous production. Herein we report the advantages of continuous production, specifically the fabrication of layerless parts. These advantages enable the fabrication of large overhangs without the use of supports, reduction of the staircasing effect without compromising fabrication time, and isotropic mechanical properties. Combined, these advantages result in multiple indicators of layerless and monolithic fabrication using CLIP technology.
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paper_title: Selective laser melting of Ti6Al4V alloy for biomedical applications: temperature monitoring and microstructural evolution

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Selective laser melting of Ti6Al4V alloy for biomedical applications: Temperature monitoring and microstructural evolution
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paper_title: Metallurgy of additive manufacturing: Examples from electron beam melting

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Abstract The metallurgy of selected metal and alloy components fabricated by additive metallurgy using electron beam melting (EBM) is presented for a range of examples including Ti-6Al-4V, Co-Cr-Mo super alloy, Ni-base super alloy systems (Inconel 625, 718 and Rene 142), Nb and Fe. Precursor and pre-alloyed powders are preheated and selectively melted using a range of EBM process parameters including beam scan strategies, beam current variations, and cooling rate features. Microstructures and residual mechanical properties are discussed for selected systems in contrast to more conventional wrought and cast products. Novel features of EBM fabrication include columnar microstructural architectures which result by layer-by-layer melt-solidification phenomena.
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paper_title: A fundamental investigation on ultrasonic vibration-assisted laser engineered net shaping of stainless steel

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Abstract Laser engineered net shaping (LENS), a laser beam deposition additive manufacturing method, has been utilized as a key technology in the direct manufacturing or repairing of metal parts. However, deposition defects such as pores, cavity, micro-cracks, residual stress, and uncertain microstructures always exist in the LENS fabricated parts, which will greatly affect the qualities and mechanical properties. In this paper, a novel ultrasonic vibration-assisted (UV-A) LENS process is proposed to reduce or eliminate the common defects due to the nonlinear actions and influences of ultrasonic vibration in molten materials. An experimental investigation is conducted on the effects of ultrasonic vibration on fabricated part geometry, powder utilization efficiency, surface roughness, geometry of molten pool and dilution zone, pores and micro-cracks, and grain size of the LENS-deposited AISI 630 stainless steel. The mechanical properties including tensile properties and hardness of the fabricated parts are evaluated and compared between UV-A LENS and LENS without ultrasonic vibration. The results show that process with ultrasonic vibration led to higher powder utilization efficiency, smaller flatness and surface roughness, and larger molten pool dimensions. Pores and micro-cracks were successfully reduced and crystal grains were significantly refined in UV-A LENS process. The improvement of these geometrical and microstructural characteristics induced by ultrasonic vibration further led to the increase in both tensile properties and hardness of LENS fabricated parts. The fundamental investigation in this work will help to establish an efficient and effective process for additive manufacturing and remanufacturing of metal parts with significantly improved qualities.
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paper_title: Production of customized hip stem prostheses – a comparison between conventional machining and electron beam melting (EBM)

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Purpose - The purpose of this paper is to study the use of the additive manufacturing (AM) method, electron beam melting (EBM), for manufacturing of customized hip stems. The aim is to investigate ...
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paper_title: Binding mechanisms in selective laser sintering and selective laser melting

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Purpose – This paper provides an overview of the different binding mechanisms in selective laser sintering (SLS) and selective laser melting (SLM), ::: thus improving the understanding of these processes. Design/methodology/approach – A classification of SLS/SLM processes was developed, based on the binding mechanism occurring in the process, in ::: contrast with traditional classifications based on the processed material or the application. A broad range of commercial and experimental SLS/SLM ::: processes – found from recent articles as well as from own experiments – was used to explain the different binding mechanism categories. ::: Findings – SLS/SLM processes can be classified into four main binding mechanism categories, namely “solid state sintering”, “chemically induced ::: binding”, “liquid phase sintering – partial melting” and “full melting”. Most commercial processes can be classified into the latter two categories, ::: which are therefore subdivided. The binding mechanism largely influences the process speed and the resulting part properties. ::: Research limitations/implications – The classification presented is not claimed to be definitive. Moreover some SLM/SLM processes could be ::: classified into more than one category, based on personal interpretation. ::: Originality/value – This paper can be a useful aid in understanding existing SLS/SLM processes. It can also serve as an aid in developing new SLS/SLM ::: processes.
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paper_title: Selective laser melting of AlSi10Mg alloy: Process optimisation and mechanical properties development

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Abstract The influence of selective laser melting (SLM) process parameters (laser power, scan speed, scan spacing, and island size using a Concept Laser M2 system) on the porosity development in AlSi10Mg alloy builds has been investigated, using statistical design of experimental approach, correlated with the energy density model. A two-factor interaction model showed that the laser power, scan speed, and the interaction between the scan speed and scan spacing have the major influence on the porosity development in the builds. By driving the statistical method to minimise the porosity fraction, optimum process parameters were obtained. The optimum build parameters were validated, and subsequently used to build rod-shaped samples to assess the room temperature and high temperature (creep) mechanical properties. The samples produced using SLM showed better strength and elongation properties, compared to die cast Al-alloys of similar composition. Creep results showed better rupture life than cast alloy, with a good agreement with the Larson–Miller literature data for this alloy composition.
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paper_title: Electron Beam Additive Manufacturing of Titanium Components: Properties and Performance

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This research evaluates the fatigue properties of Ti-6Al-4V specimens and componentsproduced by Electron Beam additive manufacturing. It was found that the fatigue per-formance of specimens produced by additive manufacturing is signiﬁcantly lower thanthat of wrought material due to defects such as porosity and surface roughness. However,evaluation of an actual component subjected to design fatigue loads did not result in pre-mature failure as anticipated by specimen testing. Metallography, residual stress, staticstrength and elongation, fracture toughness, crack growth, and the effect of post process-ing operations such as machining and peening on fatigue performance were alsoevaluated. [DOI: 10.1115/1.4025773]Keywords: additive manufacturing, electron beam, titanium, fatigue, fracture
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paper_title: Accuracy of medical models made by additive manufacturing (rapid manufacturing).

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BACKGROUND ::: Additive manufacturing (AM) is being increasingly used for producing medical models. The accuracy of these models varies between different materials, AM technologies and machine runs. ::: ::: ::: PURPOSE ::: To determine the accuracy of selective laser sintering (SLS), three-dimensional printing (3DP) and PolyJet technologies in the production of medical models. ::: ::: ::: MATERIAL ::: 3D skull models: "original", "moderate" and "worse". SLS, 3DP and PolyJet models, and a coordinate measuring machine (CMM). ::: ::: ::: METHODS ::: Measuring balls designed for measurements were attached to each 3D model. Skull models were manufactured using SLS, 3DP and PolyJet. The midpoints of the balls were determined using CMM. The distances between these points were calculated and compared with the 3D model. ::: ::: ::: RESULTS ::: The dimensional error for the PolyJet was 0.18 ± 0.12% (first measurement) and 0.18 ± 0.13% (second measurement), for SLS 0.79 ± 0.26% (first model) and 0.80 ± 0.32% (second model), and for 3DP 0.67 ± 0.43% (original model, first measurement) and 0.69 ± 0.44% (original model, second measurement), 0.38 ± 0.22% (moderate model) and 0.55 ± 0.37% (worse model). Repeatability of the measurement method was 0.12% for the PolyJet and 0.08% for the 3DP. ::: ::: ::: CONCLUSION ::: A novel measuring technique was developed and its repeatability was found to be good. The accuracy of the PolyJet was higher when compared with SLS or 3DP.
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paper_title: Mechanical evaluation of porous titanium (Ti6Al4V) structures with electron beam melting (EBM).

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Abstract Patient specific porous implants for the reconstruction of craniofacial defects have gained importance due to their better performance over their generic counterparts. The recent introduction of electron beam melting (EBM) for the processing of titanium has led to a one step fabrication of porous custom titanium implants with controlled porosity to meet the requirements of the anatomy and functions at the region of implantation. This paper discusses an image based micro-structural analysis and the mechanical characterization of porous Ti6Al4V structures fabricated using the EBM rapid manufacturing process. SEM studies have indicated the complete melting of the powder material with no evidence of poor inter-layer bonding. Micro-CT scan analysis of the samples indicate well formed titanium struts and fully interconnected pores with porosities varying from 49.75%–70.32%. Compression tests of the samples showed effective stiffness values ranging from 0.57 ( ± 0.05 ) − 2.92 ( ± 0.17 ) GPa and compressive strength values of 7.28 ( ± 0.93 ) − 163.02 ( ± 11.98 ) MPa . For nearly the same porosity values of 49.75% and 50.75%, with a variation in only the strut thickness in the sample sets, the compressive stiffness and strength decreased significantly from 2.92 GPa to 0.57 GPa (80.5% reduction) and 163.02 MPa to 7.28 MPa (93.54 % reduction) respectively. The grain density of the fabricated Ti6Al4V structures was found to be 4.423 g/cm 3 equivalent to that of dense Ti6Al4V parts fabricated using conventional methods. In conclusion, from a mechanical strength viewpoint, we have found that the porous structures produced by the electron beam melting process present a promising rapid manufacturing process for the direct fabrication of customized titanium implants for enabling personalized medicine.
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paper_title: Rapid Fabrication of Eutectic Ceramic Structures by Laser Engineered Net Shaping

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Abstract Rapid fabrication of dense ceramic structures with high-purity and complex geometry is of high demand, however, it is difficult to attain by traditional solid-phase sintering. In this paper, laser engineered net shaping system and Al 2 O 3 , Y 2 O 3 powders were utilized to fabricate ceramic structures directly without doping any binders. Influences of laser power on shaping feature were investigated by experiments and optimal process parameters were successfully achieved. Net-shaped structures of thin-wall and hollow cylinder were attained with about 15 mm section sizes. Microstructure features and properties of fabricated specimens were studied by XRD, SEM and Vickers, respectively. The deposited ceramic shows almost 100% density and stable phases mainly consisting of α-Al 2 O 3 and YAG. Microhardness is comparable to that of the product fabricated by laser zone surface melting method. The results of this research indicates that this new fabrication technique for ceramic has more flexibility compared to traditional solid-phase sintering process, and can be used for rapid fabricating of pure and complex ceramic structures.
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paper_title: Graded microstructure and mechanical properties of additive manufactured Ti–6Al–4V via electron beam melting

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Abstract Electron beam melting (EBM®)-built Ti–6Al–4V has increasingly shown great potential for orthopedic implant and aerospace applications in recent years. The microstructure and mechanical properties of EBM-built Ti–6Al–4V have been systematically investigated in this work. Its microstructure consists of columnar prior β grains delineated by wavy grain boundary α and transformed α/β structures with both cellular colony and basket-weave morphology as well as numerous singular α bulges within the prior β grains. The β phase is found to form as discrete flat rods embedded in continuous α phase and its volume fraction is determined to be ∼3.6%. Moreover, α′ martensite was not observed as it has decomposed into α and β phases. In particular, the α/β interface was studied in detail combined transmission electron microscopy with atom probe tomography. Of note is that graded Ti–6Al–4V microstructure i.e. both prior β grain width and β phase interspacing continuously increase with the build height, was observed, which mainly arises from the decreasing cooling rate. Furthermore, an increasingly pronounced strain hardening effect was also observed as the previously built layers undergo a longer annealing compared to the subsequent layers. As a result, graded mechanical properties of Ti–6Al–4V with degraded microhardness and tensile properties were found. A good agreement with the Hall–Petch relation indicates that the graded property takes place mainly due to the graded microstructure. In addition, this graded microstructure and mechanical properties were discussed based on a quantitative characterization.
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paper_title: Laser additive manufacturing of metallic components: materials, processes and mechanisms

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AbstractUnlike conventional materials removal methods, additive manufacturing (AM) is based on a novel materials incremental manufacturing philosophy. Additive manufacturing implies layer by layer shaping and consolidation of powder feedstock to arbitrary configurations, normally using a computer controlled laser. The current development focus of AM is to produce complex shaped functional metallic components, including metals, alloys and metal matrix composites (MMCs), to meet demanding requirements from aerospace, defence, automotive and biomedical industries. Laser sintering (LS), laser melting (LM) and laser metal deposition (LMD) are presently regarded as the three most versatile AM processes. Laser based AM processes generally have a complex non-equilibrium physical and chemical metallurgical nature, which is material and process dependent. The influence of material characteristics and processing conditions on metallurgical mechanisms and resultant microstructural and mechanical properties of AM proc...
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paper_title: Material properties and selection for selective laser sintering process

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Nowadays, to produce better quality products with less cost, shorter lead times, more customer delights have become the key requirements to remain competitive in the global market. To fulfil these requirements, additive manufacturing (AM) provides a technological tool for making solid free form products. Selective laser sintering (SLS) is one of the AM techniques using wide range of materials developed by various groups of technology for producing high strength parts with good aesthetic quality satisfying the customer needs. To make this technology viable, more investigation is required to improve the properties of fabricated parts, its accuracy and development of new materials for various applications. Currently, limited materials are available with very high cost that impedes growing number of applications of AM. Knowledge of SLS material properties and fabrication parameter relationship leads to appropriate selection of material for various applications without compromising the value and quality of the SLS fabricated part and customer satisfaction.
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paper_title: Additive manufacturing of biomedical implants: A feasibility assessment via supply-chain cost analysis

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Abstract The adoption of additive manufacturing (AM) for fabricating biomedical implants at hospitals provides many potential benefits. Relative to biomedical implants fabricated via traditional manufacturing (TM), typically available by suppliers out of the immediate region, biomedical implants fabricated through AM provides an opportunity to receive more patient-specific, customized parts with faster response, a lower inventory level, and reduced delivery costs. Despite the promising features of AM technologies, the make-or-buy decisions are not straightforward and require careful investigation due to the relatively high AM machine and production costs. Most of the existing studies focus on the analysis of process-level costs, which are usually evaluated/calculated based on individual AM processes. No research efforts, to the best of our knowledge, have been dedicated to the quantitative analysis of the costs of supply chains integrated with AM facilities, e.g., inventory cost, transportation cost, product lead time, etc. In this study, we propose a stochastic cost model to quantify the supply-chain level costs associated with the production of biomedical implants using AM techniques, and investigate the economic feasibility of using such technologies to fabricate biomedical implants at the sites of hospitals. The problem is formulated in the form of a stochastic programming model, which determines the number of AM facilities to be established and volume of product flow between manufacturing facilities and hospitals. A customized Sample Average Algorithm (SAA) is developed to obtain the solutions. We apply the cost model to a real-world case study that focuses on the use of biomedical implants for hospitals in the state of Mississippi (MS), and identify the conditions and cost parameters that have significant impact on the economic feasibility of AM. We find that the ratio between the unit production costs of AM and TM (ATR), as well as product lead time and demands, are key cost parameters that determine the economic feasibility of AM.
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Title: Manufacturing Methods for Medical Artificial Prostheses– A Review

Section 1: INTRODUCTION
Description 1: Provide an overview of the field of prosthetics, its objectives, different types of prostheses, and the importance of manufacturing methods for medical applications.

Section 2: Conventional Manufacturing Methods
Description 2: Discuss traditional methods such as machining, incremental sheet forming (ISF), and investment casting, including their processes, advantages, and limitations.

Section 3: Additive Manufacturing Methods
Description 3: Detail the various additive manufacturing technologies such as Fused Deposition Manufacturing (FDM), Stereolithography (SLA), Continuous Liquid Interface Production (CLIP), Selective Laser Sintering (SLS), and Electron Beam Melting (EBM), focusing on their applications, benefits, and drawbacks.

Section 4: Platform
Description 4: Describe powder-based AM, including Laser Engineered Net Shaping (LENS) and other relevant technologies, discussing their specific applications in medical prostheses manufacturing.

Section 5: CONCLUSION
Description 5: Summarize the advancements in manufacturing technologies for medical implants, comparing conventional and additive methods, and discuss future trends and potential improvements in the field.