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Over the last decade, the enormous potential of metal additive manufacturing (AM) processes has led these technologies to establish their position in many industries. Much effort is being made toward their widespread application; however, much remains to be done to achieve full industrialization of these processes. Therefore, many companies, research centers and universities are investing in comprehensive research and development activities in order to further promote the industrialization of metal AM. This review traces the progress of metal AM technologies through an investigation of patents. In the present study, beam-based metal AM patents were searched through the Orbit Intelligence database. First, the number of patents per year was studied, indicating that, as expected, there is strong growth in AM patenting activities. The patents were afterward examined in order to highlight the key players in the field, and it was found that the main players investing in this market are: multidisciplinary companies, AM machine producers, end users working, especially in the aerospace sector, universities and research centers. The patents were then analyzed to understand the technology domains covered by each key player and their trend of investments. Finally, the patents in the field of Materials and Metallurgy were studied individually to identify the main topics faced by the most used alloy classes: Al-, Ni- and Ti-based alloys and steels. The extensive study of these patents clearly indicated that the main gaps to fill in metal AM are strongly material dependent and that it is possible to find correlations between the alloy classes, their main industrial applications and their specific AM processability issues. The current study provides insights into global trends that can help industrial markets to identify the right investment direction and research to identify topics for future investigation.

3D printing has been widely adopted not only by individuals or people printing in the community, such as the Markers’ movement but also by industries from different sectors. Unlike traditional manufacturing technologies, layer-wise manufacturing enables live monitoring of the process and part quality layer after layer through proper sensors installed in the working volume of the 3d printing system. Therefore, from the sustainability perspective, unnecessary waste of material and energy can be avoided by aborting the fabrication when a serious defect is detected in one or more layers. In this paper, a low-cost camera and computer vision algorithms are used for the implementation of an in-situ monitoring system for open 3D printing. After printing each layer, the step of image capture is introduced by modification of the open ISO G-code file. The image of the single part layer is then compared to the information extracted from the G-code for automatic detection of manufacturing defects. The area of missing or exceeding material is computed and shown to the user, which can decide to cancel the job in case of important flaws to avoid any unnecessary waste in terms of material, time and costs.

Screw-extrusion-based 3D printing or fused granular fabrication (FGF) is a less widespread variant of filament-based 3D printing for polymers. An FGF printer can be fed directly from polymer granules for improved sustainability. Shorter manufacturing routes and the potential of using recycled pellets from waste plastics are key features of FGF in the circular economy framework. A modified version of a standard Prusa i3 plus printer, which was equipped with a Mahor screw extruder, is used to test the mechanical performance of polylactic acid (PLA) processed with different layer infill and printing speed. Rheological and thermal analyses are carried out to characterise the material. The energy consumption of the FGF printer was measured during the fabrication of Dumbbell specimens. Tensile test results are consistent with other investigations presented in the literature. A higher printing speed promotes FGF eco-efficiency without a detrimental effect on the material strength, whereas lower printing speed should be preferred for increased material stiffness.

Leiomyosarcomas are rare and aggressive tumors characterized by a complex karyotype. Surgical resection with or without radiotherapy and chemotherapy is the standard curative treatment. Unfortunately, a high percentage of leiomyosarcomas recurs and metastasizes. In these cases, doxorubicin and ifosfamide represent the standard treatment but with low response rates. Here, we evaluated the induction of proteotoxic stress as a possible strategy to kill leiomyosarcoma cells in a therapeutic perspective. We show that aggressive leiomyosarcomas coexist with high levels of proteotoxic stress. As a consequence, we hypothesized that leiomyosarcoma cells are vulnerable to further increases of proteotoxic stress. The small compound 2c is a strong inducer of proteotoxic stress. In leiomyosarcoma cells, it triggers cell death coupled to a profound reorganization of the mitochondrial network. By using stimulated emission depletion microscopy, we have unveiled the existence of DIABLO/SMAC clusters that are modulated by 2c. Finally, we have engineered a new version of 2c linked to polyethylene glycol though a short peptide, named 2cPP. This new prodrug is specifically activated by proteases present in the tumor microenvironment. 2cPP shows a strong antitumor activity in vivo against leiomyosarcomas and no toxicity against normal cells.

Electron beam melting (EBM) process is an additive manufacturing process largely used to produce complex metallic components made of high-performance materials for aerospace and medical applications. Especially, lattice structures made by Ti–6Al–4V have represented a hot topic for the industrial sectors because of having a great potential to combine lower weights and higher performances that can also be tailored by subsequent heat treatments. However, the little knowledge about the mechanical behaviour of the lattice structures is limiting their applications. The present work aims to provide a comprehensive review of the studies on the mechanical behaviour of the lattice structures made of Ti–6Al–4V. The main steps to produce an EBM part were considered as guidelines to review the literature on the lattice performance: (1) design, (2) process and (3) post-heat treatment. Thereafter, the correlation between the geometrical features of the lattice structure and their mechanical behaviour is discussed. In addition, the correlation among the mechanical performance of the lattice structures and the process precision, surface roughness and working temperature are also reviewed. An investigation on the studies about the properties of heat-treated lattice structure is also conducted.

Metal components produced by Additive Manufacturing (AM) technologies usually exhibit a rough surface, that in certain applications can result detrimental for the part’s functionality. Thus, it is of great interest to study the finishing processes that can be applied to the surfaces, both external and internal, of AM components. The aim of this work is the evaluation of the capabilities of a vibro-finishing process in the treatment of samples produced by Laser-Powder Bed Fusion (L-PBF) from AlSi10Mg powders. In this research, the abrasive media is identified, and the surface quality improvement is analysed in terms of surface roughness and modifications induced by the finishing treatment (i.e., edge rounding, material loss) against finishing duration. The cost of the treatment is also evaluated.

Low-cost entry-level 3D printers suffer from reduced optimization, that is a consequence of development cost savings. A student challenge was used to modify four Prusa i3 machines with the aim of enhancing the design and performances by means of self-replicated parts. The challenge results were assessed through benchmarking of the four modified 3D printers, whose dimensional accuracy was evaluated by means of CMM measurements of 3D printed replicas of a reference part. The ISO IT grades related to the dimensional quality of the replicas were considered in the analysis of the CMM measures for the challenge assessment.

This paper provides an overview on the main additive manufacturing/3D printing technologies suitable for many satellite applications and, in particular, radio-frequency components. In fact, nowadays they have become capable of producing complex net-shaped or nearly net-shaped parts in materials that can be directly used as functional parts, including polymers, metals, ceramics, and composites. These technologies represent the solution for low-volume, high-value, and highly complex parts and products.

For more than thirty percent of patients with implant-supported fixed dental prosthesis, various complications can be observed over five-years of function. In some cases, failure can be ascribed to mechanical reasons such as loosening of the retaining screws or fracture of the implant components. The paper evaluates three different failures of implant-supported prostheses. All cases were analyzed by optical and SEM microscopy to identify the failure modes and the possible failure causes. Improper design or errors in finishing operations or in assembly are identified as dental failure causes. A matrix classification is proposed to collect rupture cases of implant-supported prostheses.

Additive manufacturing technologies are currently envisaged to boost the development of a next generation of microwave devices intended for satellite telecommunications. Due to their excellent electromagnetic and mechanical properties, metal waveguide components are key building blocks of several radio frequency (RF) systems used in these applications. This article reports the perspectives deriving from the use of laser powder bed fusion (L-PBF) technology to the production of high-performance microwave waveguide devices. A robust design of filters has been implemented in several prototypes manufactured in AlSi10Mg alloy. The corresponding measured performance confirm the applicability of the L-PBF process to the intended applications

An additive manufacturing process should produce repeatable results as far as the properties of the material and the geometric dimensions that have to be adopted by a company as a production method are concerned. This represents a challenge for such high-volume sectors as the automotive industry, where quality and reliability are extremely important. One way of addressing this challenge is to qualify the process. A common framework has here been identified starting from the analysis of the factors that influence the stability of the result in the main phases of metal powder bed fusion (PBF) processes. A qualification procedure (QP), which offers possible solutions to help reduce risk factors, has been proposed. This procedure is independent of the industrial sectors, of which type of materials and metal PBF processes, and of the manufacturer of the used PBF system.

Electro-discharge machining (EDM) of thin deep features widens processing opportunities of difficult-to-cut materials, such as Ni-based alloys, towards attractive industrial applications. Conversely, the complex interaction between electrical, thermal, and chemical phenomena in EDM thwarts process modeling and prediction. As a matter of fact, recent experimental discoveries encourage setting forth a new theory of discharge ignition in the gap, based on the role of debris, which lays foundations for a recursive mathematical model showing a chaotic evolution. The paper reports on electro-discharge drilling of small deep holes in Inconel 718. Process performances are measured with varying electrode size and geometry, attesting a pivotal effect of gap pollution on productivity and on the onset of a secondary detrimental removal of material by intergranular corrosion. All findings support the emerging model for discharge ignition via debris bridges, and, most notably, debris chains are documented for the first time in the field of metals, second only to a previous case for a ceramic composite. On the whole, the paper provides conclusive validation of the role of debris in the ignition of discharges.

Electron Beam Melting (EBM) has the potentiality of being an effective system in terms of time and energy consumption. Among the different additive manufacturing processes that are available, the EBM process has shown the lowest Specific Energy Consumption (SEC) and the highest average Deposition Rate (DRa). However, there appears to be a lack of literature on the correlation between SEC and DRa. Moreover, all the literature studies have only an analysis of energy efficiency during the melting of the bulk material phase and have adopted a fixed job design. Therefore, the aim of this study has been to fill this gap. The EBM process is decomposed into small substeps and a bottom-up approach is adopted to provide models that can be used to evaluate the energy of each process subphase and to perform an energy characterisation at the unit process level. A black-box approach is applied to provide a new model for the energy efficiency of the EBM process. Different jobs have been designed to analyse the effect of a part and of manufacturing designs. Bulk material, support and lattice structures have been included. The design has therefore been aimed at investigating the effect of the building height, melted area and process themes on energy efficiency. The jobs have been produced using Arcam A2X and Standard Arcam Ti6Al4V powders. According to this research, the architecture of the machine and its control of the process have the main impact on the relationship between SEC and DRa. The design features of the part and of the job influence the position of the job on this curve and thus the relative energy and time efficiency. Additionally, the empirical approach applied to the machine subunits has highlighted that only a small part of the total energy demand is needed to power the electron beam during the melting phase, while the remaining part guarantees the good machine working conditions.

Purpose – The purpose of this paper is to report an interdisciplinary, cooperative-learning project in a second-year course within the “Enzo Ferrari” Master of Science Degree in Mechanical Engineering. The work aims to raise awareness of the educational impact of additive manufacturing and reverse engineering. Design/methodology/approach – Students are asked to develop, concurrently, the design and the manufacturing solution for an eye-tracker head mount. A digital head model is reverse engineered from an anatomical mannequin and used as an ergonomic mock-up. The project includes prototype testing and cost analysis. The device is produced using additive manufacturing techniques for hands-on evaluation by the students. Findings – Results of the presented case study substantiate the authors’ belief in the tremendous potential of interdisciplinary project-based learning, relying on innovative technologies to encourage collaboration, motivation and dynamism. Originality/value – The paper confirms a spreading conviction that the soon-to-be engineers will need new practice-oriented capabilities to cope with new competitive scenarios. Engineering education must adapt to the social, rather than industrial, revolution that is being brought about by additive fabrication.

Specific features of software for computer aided inspection are detailed.Six commercial software packages are tested and compared through a fuzzy AHP analysis.GD&T functions and algorithms are not mature yet to provide consistent results.More expensive software with advanced features provide higher performances.The freeware Gom Inspect is a valid choice for basic inspection activities. Industrial metrology of mechanical components has been facing a gradual revolution recently through the application of contactless 3D scanners in computer aided inspection. Following the industrial trend and request, new modules for quality control activities on scan data have been integrated in reverse engineering software packages.The aim of this work is to propose a structured methodology for the screening and comparison of reverse engineering programs that are suitable for inspection activities. Specific features that distinguish this kind of software are described and detailed. Six different commercial software are tested using invariant scan data from a reference part that was specifically designed for inspection purposes.The selected packages are then compared by means of a multicriteria fuzzy AHP analysis that considers quantitative and qualitative criteria. The criteria were grouped into three categories related with the user, the vendor and the technical requirements. Two different scenarios are considered for the choice of the software that best suits to computer aided inspection activities.

The paper addresses the dimensional tolerance and assembly accuracy of prosthetic components obtained by different manufacturing processes. The success of single tooth implant replacements hangs on the stability of the hexagonal connection, but no standard control procedures are available for its evaluation. The research aims at proposing a new protocol for the dimensional assessment of implant-abutment connections, based on non-contact measurement and statistical data processing. The procedure is applied to machined- and cast-on abutments, as well of the matching implants. Samples are measured using an optical measuring microscope and data are processed to obtain the international tolerance (IT) grade. The rotational misfit is then calculated using the apothems of the external and the internal hexagon. As to the results, all the components are classified between IT8 and IT9 and the maximum rotational misfit is around 4° for all the assemblies, inferior to the critical limits for the screw joint stability. An objective dimensional characterization of prosthetic components and assemblies is reported, which is the basis for their reliability in clinical applications. From a wider perspective, an original measuring protocol is proposed, independent of parts assembly and based on international tolerances.

Additive Manufacturing (AM) and 3D printing are drivers for material savings in manufacturing. Owing to the continuous diffusion of 3D printing driven by low-cost entry-level material extrusion printers, sustainability of a so popular AM technology is of paramount importance. Therefore, recycling 3D printed wastes and 3D parts again at the end of their life is an important issue to be addressed. Research efforts are directed towards the improvement of the biodegradability of 3D printing filaments and the replacement of oil based feedstock with bio-based compostable plastics. The aim of this work is to describe the state of the art about development and use of recycled or biodegradable filaments in 3D printing. Beyond a critical review of the literature, open issues and research opportunities are presented.

Casting process simulation is nowadays established as a strategic tool in process optimisation to improve product quality. However, sometimes the required three-dimensional mathematical model of the casting is not available, because the original drawings are not-up-to date and parts are subjected to design changes. In these cases, reverse engineering (RE) is the most suitable method to reconstruct the geometrical model of the casting. In this paper, a RE-based procedure is proposed to obtain the three-dimensional CAD model of a casting from its physical equipment. The proposed procedure involves four phases: pre-digitising, digitising of equipment parts, surface reconstruction, and three-dimensional CAD modelling. An aeronautical part fabricated by sand casting is selected as case study to verify the feasibility of this approach. Outcomes prove that the RE methodology is adequate to virtually reconstruct the geometry of each single part of the equipment as well as the whole geometry of the assembl...

3D printing is widely used in the entertainment industry by filmmakers, effect studios and game designers to easily and fast fabricate characters or objects that are first virtually modelled through Computer Graphics. There are several commercial proposals in the field of low-cost 3D printers, with prices starting from a few hundred euros for kits that the users should assemble by themselves. However, their performances in terms of part accuracy are quite limited and are basically the consequence of a lack of optimization both in mechanical terms as in software. Starting from these considerations, an optimization project was assigned to the students of the Specializing Master in Industrial Automation of the Politecnico di Torino. The Master is developed in collaboration with COMAU S.p.a., a company worldwide leader in automation expecially for the automotive sector. The task of enhancing the performances of the 3D printer Prusa i3, that is supplied in the assembly box, was assigned to sixteen engineers attending the Master who were divided into 4 groups. The activities have led to the birth of four new 3D printers: Fluo, Ghost, Metallica and Print-Doh. In order to assess and validate the improvements, a benchmarking activity was carried out to evaluate the dimensional accuracy of the four printers. The benchmarking was based on the manufacturing of an innovative reference artifact whose geometrical features are designed to fit within different ISO basic sizes. Each group printed a replica of the reference part with their own new printer and then the replicas were measured by means of a coordinate measuring machine (CMM). Measures were used to compare the performances of the four printers and the results of the benchmarking considers the dimensional accuracy of the replicas in terms of ISO IT grades, but also the form errors of the geometrical features through GD&T tolerances.

An innovative benchmark representing a dental arch with classic features corresponding to different kinds of prepared teeth is proposed. Dental anatomy and general rules for tooth preparation are taken into account. This benchmark includes tooth orientation and provides oblique surfaces similar to those of real prepared teeth. The benchmark is produced by additive manufacturing (AM) and subjected to digitization by a dental three-dimensional scanner. The evaluation procedure proves that the scan data can be used as reference model for crown restorations design. Therefore this benchmark is at the basis for comparative studies about different CAD/CAM and AM techniques for dental crowns.

In foundry industries as well as in many other sectors, inspection practice has been facing a gradual revolution through the introduction and development of optical scanners in recent years. The main advantage of contactless quality control is that the external geometry of the cast tool or cast part can be completely inspected in short times by retrieving the coordinates of hundreds of thousands of points. The role and importance of the alignment operation in part inspection is undeniable since any error leads to an unreliable inspection of the part. Therefore, the definition of part reference systems on scan data for computer aided inspection is a crucial operation. The aims of this paper are to highlight this issue and to point out how an improper procedure for part alignment can lead to an incorrect evaluation of real part deviations, especially when the accuracy of the scan data is low.

PurposeThe purpose of this paper is to highlight how rapid manufacturing (RM) of plastic parts combined with part redesign could have positive repercussion on cost saving.Design/methodology/approachComparison between two different technologies for plastic part production, the traditional injection molding (IM) and the emergent RM, is done with consideration of both the geometric possibilities of RM and the economic aspect. From an extended literature review, the redesign guidelines and the cost model are identified and then applied to a component selected for its shape complexity. It is an assembly that was redesigned for RM purpose, in order to take advantage of additive manufacturing potentialities. The geometric and economic differences between IM and RM are discussed.FindingsThis research evidences that currently in Western Europe RM combined with redesign can be economically convenient and competitive to IM for medium volume production of plastic parts. Consequently, this is a great opportunity to keep the production in Europe instead of moving it overseas.Research limitations/implicationsAs regards manufacturing costs, results presented in this study are mainly based on cost estimation provided by Italian companies and it is assumed that the plant is located in Western Europe.Practical implicationsThe research assesses the feasibility of making functional and operational plastic parts without the use of traditional manufacturing processes by redesign for RM.Originality/valueTwo different kinds of research papers comparing RM and IM exist in literature: on the one hand, the two techniques are evaluated from the economical point of view, on the other, the part redesign is analyzed. No paper considers the interrelation between redesign and cost estimation. In this work, these aspects are combined to point out that a remarkable cost reduction is obtained when the component shape is modified to exploit RM advantages.

Many automotive applications require deep drilling on pressure die-cast parts in Aluminium alloys. The aim of the research was to understand if common cutting practices, usually determined on raw materials, can be successful on semimanufactured parts as well, having an inhomogeneous microstructure. A specific investigation was carried out on deep drilling of an EN AB-46000 cylinder block, varying technological parameters (cutting speed, feed, tool, lubrication). Dimensional tolerance and surface roughness were measured and statistically analyzed. The quantitative analysis of the process macroscopic performances was combined with an investigation of microstructural aspects of the material, their effects on chip formation and tool-chip interaction.

PurposeThe purpose of this paper is to verify the feasibility and evaluate the dimensional accuracy of two rapid casting (RC) solutions based on 3D printing technology: investment casting starting from 3D‐printed starch patterns and the ZCast process for the production of cavities for light‐alloys castings.Design/methodology/approachStarting from the identification and design of a benchmark, technological prototypes were produced with the two RC processes. Measurements on a coordinate measuring machine allowed calculating the dimensional tolerances of the proposed technological chains. The predictive performances of computer aided engineering (CAE) software were verified when applied to the ZCast process modelling.FindingsThe research proved that both the investigated RC solutions are effective in obtaining cast technological prototypes in short times and with low costs, with dimensional tolerances that are completely consistent with metal casting processes.Practical implicationsThe research assessed the feasibility and dimensional performances of two RC solutions, providing data that are extremely useful for the industrial application of the considered technologies.Originality/valueThe paper deals with experimental work on innovative techniques on which data are still lacking in literature. In particular, an original contribution to the determination of dimensional tolerances and the investigation on the predictive performances of commercial CAE software is provided.

Purpose – The purpose of this paper is to evaluate how the direct access to additive manufacturing (AM) systems impacts on education of future mechanical engineers, within a Master’s program at a top Italian University. Design/methodology/approach – A survey is specifically designed to assess the relevance of entry-level AM within the learning environment, as a tool for project development. The survey is distributed anonymously to three consecutive cohorts of students who attended the course of “computer-aided production (CAP)”, within the Master of Science Degree in Mechanical Engineering at Politecnico di Torino. The course includes a practical project, consisting in the design of a polymeric product with multiple components and ending with the production of an assembled prototype. The working assembly is fabricated by the students themselves, who operate a fused deposition modelling (FDM) machine, finish the parts and evaluate assemblability and functionality. The post-course survey covers diverse aspects of the learning process, such as: motivation, knowledge acquisition, new abilities and team-working skills. Responses are analyzed to evaluate students’ perception of the usefulness of additive technologies in learning product design and development. Among the projects, one representative case study is selected and discussed. Findings – Results of the research affirm a positive relationship of access to AM devices to perceived interest, motivation and ease of learning of mechanical engineering. Entry-level additive technologies offer a hands-on experience within academia, fostering the acquisition of technical knowledge. Research limitations/implications – The survey is distributed to more than 200 students to cover the full population of the CAP course over three academic years. The year the students participated in the CAP course is not tracked because the instructor was the same and there were no administrative differences. For this reason, the survey administration might be a limitation of the current study. In addition to this, no gender distinction is made because historically, the percentage of female students in Mechanical Engineering courses is about 10 per cent or lower. Although the answers to the survey are anonymous, only 37 per cent of the students gave a feedback. Thus, on the one hand, impact assessment is limited to a sample of about one-third of the complete population, but, on the other hand, the anonymity ensures randomization in the sample selection. Practical implications – Early exposure of forthcoming designers to AM tools can turn into a “think-additive” approach to product design, that is a groundbreaking conception of geometries and product functionalities, leading to the full exploitation of the possibilities offered by additive technologies. Social implications – Shared knowledge can act as a springboard for mass adoption of AM processes. Originality/value – The advantages of adopting AM technologies at different levels of education, for diverse educational purposes and disciplines, are well assessed in the literature. The innovative aspect of this paper is that the impact of AM is evaluated through a feedback coming directly from mechanical engineering students.

In the industrial field, the fabrication of custom fixtures was historically one of the first applications of Rapid Prototyping technologies for end-product manufacturing. The advantage of using additive manufacturing custom fixtures is well assessed in literature in terms of production times and costs, whereas little attention was given to the life time and wear behaviour of additive manufacturing fixtures. A specific apparatus was designed for a novel wear test, whose results provide information about the durability of fixtures fabricated by fused deposition modelling to be used for the inspection of sheet metal parts

In this work a procedure to obtain the three-dimensional CAD model of a casting from the physical equipment is proposed. In fact, the actual geometry of the cast part cannot be used for process simulation because of the shrinkage and deformation occurring during the casting process. The procedure is based on reverse engineering tools and involves four steps: pre-digitizing, digitizing, surfaces reconstruction, and three-dimensional CAD modelling. Critical issues are identified and discussed in this paper. To verify this procedure, it is applied to an aeronautical part fabricated by sand casting. Results prove that this RE approach is adequate to virtually reconstruct the single geometry of each equipment part and of the whole assembled mould. The three-dimensional CAD model is demonstrated to be suitable for CAE analysis, leading to a finite element mesh that meets requirements of casting simulation. Furthermore it is easily editable to adapt the design according to numerical outputs

In recent years, digitizing and automation have gained an important role in manufacturing of dental devices. Instead of the traditional plaster model procedure, scanning techniques may be used for the geometry acquisition. Point clouds are processed and converted into standard CAD models, from which metal tooth cap can be fabricated by milling, integrating CAM tool, or by rapid manufacturing (RM) techniques. Good quality control is critical to ensure the crown fit: an improper fit could cause crown falling off. So far there is no standard procedure for evaluating quality of both 3D digitization and milling/RM cap making processes. Thus, a specific benchmark is designed to represent critical features of a stone replica, like a dental arch with studs resembling teeth prepared for crowns installation. The benchmark is then produced and measured by means of a coordinate measuring machine

Modern CAD/CAM techniques together with five-axis high-speed milling allow to reduce moulds manufacturing time and costs. Nevertheless, in order to put a mould into use, operations of manual finishing and fitting are still always required. Such operations, performed manually by mould makers, modify the milled surfaces of moulds. Reverse engineering techniques can be employed in quality control to evaluate dimensions and geometrical tolerances on moulds after machining and fitting. Changes in the product’s shape are sometimes decided after a mould has already been machined. In such cases, if possible, the mould maker directly modifies the mould. Thus the final real geometry of the mould does not reflect the one of the original CAD model. The aim of this paper is to point out the benefits of non-contact quality control and to illustrate a procedure, based on reverse engineering techniques, to reconstruct and update the mathematical model of the mould after it has been polished and fit. The procedure was tested on a mould for the production of a plastic camera body that was previously inspected by means of a structured light scanner.

PurposeTo introduce an innovative method for the design of supporting elements to be applied to the free‐form components during the dimensional control.Design/methodology/approachThis paper shows an innovative procedure based on reverse engineering and rapid prototyping techniques for the realization of fixtures fitting the geometry of free‐form elements. The application of the procedure have been made on a sheet metal free‐form element. After the design and manufacturing of the supporting elements, some uniformly distributed measurements have been made on the sheet metal component. A coordinate measuring machine (CMM) has been used in order to get dimensional information and to give the IT class location of the component.FindingsThe use of the CMMs for the dimensional control of the production elements requires the availability of an adequate supporting system above all if the control concerns free‐form components with complex forms. This influences considerably the final quality of the measurements mainly if the control concerns free‐form components with complex forms, not bound to classic geometric entities. The supporting systems commonly used foresee the utilization of standard elements (clamps, magnets, suction cups and plates and others) ideal for the parts with regular geometry but that can cause inconveniences if applied to free‐form elements and long times for the part supporting. The supporting elements of our paper fit to the geometry of free‐form component.Research limitations/implicationsFor the production of the supporting elements, the chosen technique has been the selective laser sintering with the use of the Pa‐Al powders (alumide). This material has a limited mechanical resistance such to guarantee a control up to 500 parts. For this reason, in a future research we would produce these fixtures using sintered metal materials.Practical implicationsThe possibility to guarantee a correct dimensional control in the case of free form components using fixtures that fit to the geometry of free form components.Originality/valueThe paper shows an innovative procedure to get fixturing elements that fit to the geometry of free‐form component and provide stability and immobility to the component during the inspection phase.

Dimensional accuracy and surface finish are the cornerstone of Rapid Prototyping (RP) especially if the models will be used for the production of tools as mould or EDM electrodes. The paper deals with the development, manufacture and testing of benchmark to investigate dimensional accuracy and surface finish. A new technique of checking the machine quality of a RP workpiece according to the ANSI-ISO standards is presented. Moreover the surface of RP model were observed by SEM microscope.

The diffusion of Fused Deposition Modeling (FDM) was recently boosted by the expiration of the FDM patent and the subsequent worldwide development of low cost FDM machines by a huge number of small companies. In most of the cases, FDM machines are worth what they cost. Thus the performance of expensive industrial FDM systems is better than that of low cost machines, also known as 3D printers.In this paper a benchmarking is carried out between a Dimension EliteTM by Stratasys and a 3D TouchTM by Bits from Bytes (BFB). The study and comparison is based on a reference part that was designed to fit into the building volume of most of low cost FDM machines. The part includes several classic geometries (planes, cylinders, spheres and cones) of different sizes to cover several ranges of basic sizes as defined by the ISO 286 standard. Geometric features appear both in the concave and convex shapes to account for all design possibilities. The proposed reference part allows to consider a higher number of features for each range of basic sizes with respect to other benchmarking models presented in the literature. Moreover the part does not require support structures for its production, allowing for manufacturing on 3D printers that come with a unique extruder. Replicas of the reference part are printed out of ABS (acrylonitrile butadiene styrene) material with different layer thicknesses using the compared machines. After inspecting the replicas by means of a Coordinate Measuring Machine (CMM), the dimensional accuracy of the compared FDM systems is reported through part quality using IT grades associated with the ISO basic sizes. GD&T values are also evaluated for some of the geometric features appearing on the reference part.

In this work a procedure for evaluating the accuracy of novel manufacturing methods of dental crowns is proposed. The procedure is based on a benchmark specifically designed for dental application. The evaluation procedure starts with the achievement of the Reference Model (ReM), consisting of actual dimensions of the reference artefact. Then the benchmark is digitized. The point-cloud (Virtual Benchmark -VB) is inspected by using a specific RE software to evaluate the accuracy of the digitization step. Thereafter caps are designed and manufactured. After fabrication, the coupling surface of each manufactured cap is inspected and compared with the VB and the ReM to provide information about the accuracy of the manufacturing process and of the whole crown restoration production process, respectively. Two recent techniques are analysed: investment casting of cobalt-chromium (CoCr) alloy from drop-on-demand (DoD) wax patterns and milling of zirconia

Direct Metal Laser Sintering (DMLS) is capable of producing complex shaped metallic parts with superior mechanical properties than those obtained from conventional processes. Thus the application of this technology is increasing in aerospace, automotive and also in medical fields. The high mechanical performances of metal parts are mainly due to the rapid melting and solidification of the powder. As a consequence a very fine microstructure is obtained. Moreover the parts are subjected to further post-processing operations, such as shot-peening or polishing, to improve the outer surface finish. This article is focused on the investigation of the mechanical properties of AlSi10Mg parts produced by DMLS. Thus tensile and Charpy specimens are produced and tested in the "as-built" status and after different post-processing conditions. The results show that the post-processing operations enhance the mechanical properties of DMLS parts.

The recent development of non-contact digitizing systems dedicated to dental applica- tions has introduced innovative procedures, based on Reverse Engineering techniques, for the production of artificial teeth. Starting from the reconstructed 3D model of each tooth, first the mould CAD model is created and then the milling path is computed for machining. At the moment there is no indication of the quality of such innovative procedure, so it is investigated in this study by evaluating the deviation intro- duced by each manufacturing step. A machined mould for the production of acrylic molars and premo- lars is inspected by means of a contactless scanner and some teeth are selected as manufactured samples. Scan data of such samples allow to evaluate the deviations introduced by each operation. A comparison of two optical digitizers is based on the results of this study and economic considerations related to costs and times are also included.