Alessandro Bove, Fulvio Lieske, Flaviana Calignano and Luca Iuliano
Material extrusion (MEX) is one of the most known techniques in the additive manufacturing (AM) sector to produce components with a wide range of polymeric and composite…
Abstract
Purpose
Material extrusion (MEX) is one of the most known techniques in the additive manufacturing (AM) sector to produce components with a wide range of polymeric and composite materials. Moisture causes alterations in material properties and for filaments strongly hygroscopic like nylon-based composites this means greater ease of deterioration. Drying the filament to reduce the moisture content may not be sufficient if the humidity is not controlled during printing. The purpose of this study is to achieve the recovery of a commercial nylon-based composite filament by applying process optimization using an open source MEX machine.
Design/methodology/approach
A statistical approach based on Taguchi’s method allowed to achieve an ultimate tensile strength (UTS). A verification of the geometrical capabilities of the process has been performed according to the standard ISO/ASTM 52902-2019. Chemical tests were also carried out to test the resistance to corrosion in acid and basic solutions.
Findings
An UTS of 71.37 MPa was obtained, significantly higher than the value declared by the filament’s manufacturer (Stratasys Inc., USA). The best configuration of process parameters leads to good geometrical deviations for flat surfaces, in a range of 0.01 and 0.38 for flatness, while cylindrical faces showed more important deviations from the nominal values. The good applicability of the material in corrosive environments has been confirmed.
Originality/value
This study examined the performance restoration potential of a nylon composite filament that was significantly affected by storage conditions. For the filament manufacturer, if the material remains in ambient air for an hour or idle in the machine for more than 24 h, the material may no longer be suitable for printing. The study highlighted that the drying of the filament must not be temporary but constant to guarantee printability, and, by acting on the process parameters, it is possible to obtain better mechanical properties than declared by the manufacturer.
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Eleonora Atzeni, Luca Iuliano, Paolo Minetola and Alessandro Salmi
The 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.
Abstract
Purpose
The 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/approach
Comparison 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.
Findings
This 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/implications
As 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 implications
The research assesses the feasibility of making functional and operational plastic parts without the use of traditional manufacturing processes by redesign for RM.
Originality/value
Two 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.
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Maria Grazia Violante, Luca Iuliano and Paolo Minetola
To introduce an innovative method for the design of supporting elements to be applied to the free‐form components during the dimensional control.
Abstract
Purpose
To introduce an innovative method for the design of supporting elements to be applied to the free‐form components during the dimensional control.
Design/methodology/approach
This 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.
Findings
The 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/implications
For 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 implications
The 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/value
The 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.
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Elena Bassoli, Andrea Gatto, Luca Iuliano and Maria Grazia Violante
The 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…
Abstract
Purpose
The 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/approach
Starting 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.
Findings
The 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 implications
The 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/value
The 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.
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Paolo Minetola, Luca Iuliano, Elena Bassoli and Andrea Gatto
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…
Abstract
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.
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Paolo Minetola and Luca Iuliano
– The purpose of this paper is to present a custom-built tribometer that mimics the wear of additive manufactured fixtures used in inspection of sheet metal components.
Abstract
Purpose
The purpose of this paper is to present a custom-built tribometer that mimics the wear of additive manufactured fixtures used in inspection of sheet metal components.
Design/methodology/approach
Referring to the inspection of sheet metal parts, the fixture undergoes sliding wear during loading and unloading phases of the quality control operation. A new wear test is proposed to mimic the actual wearing conditions of the fixtures because the standards are deemed insufficient. In the tribometer, a cylindrical Alumide cantilever beam is made to slide back and forth inside a slightly bigger hole cut into a nickel-plated steel sheet. The sheet is spring loaded such that it applies a force on the specimen. The wear on the beam is measured after every 500 cycles of the beam motion.
Findings
Results of some first test trials are reported to evaluate the durability of Alumide fixtures fabricated by selective laser sintering. The results are also compared to those obtained for a machined fixture made of an Al-Cu alloy.
Practical implications
The proposed wear test estimates the life time of additive manufactured fixtures in terms of numbers of inspected components. The test can be extended to different materials to compare their durability.
Originality/value
Today, the fabrication of custom fixtures by means of additive manufacturing technologies is a reality in many manufacturing industries. The advantage of using those production technologies for custom fixtures is well assessed in literature in terms of manufacturing times and costs, whereas little attention was given to the life time and wear behaviour of fabricated fixtures. For its practical implication, the fixture durability is indeed very important for manufactures.
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Manickavasagam Krishnan, Eleonora Atzeni, Riccardo Canali, Flaviana Calignano, Diego Manfredi, Elisa Paola Ambrosio and Luca Iuliano
The aim of this research is to reach a deep understanding on the effect of the process parameters of Direct Metal Laser Sintering process (DMLS) on macroscopic properties…
Abstract
Purpose
The aim of this research is to reach a deep understanding on the effect of the process parameters of Direct Metal Laser Sintering process (DMLS) on macroscopic properties (hardness and density) of AlSi10Mg parts and resulting microstructure.
Design/methodology/approach
A full factorial design of experiment (DOE) was applied to determine the most significant process parameter influencing macroscopic properties of AlSi10Mg parts manufactured by DMLS process. The analysis aims to define the optimum process parameters and deduce the process window that provides better macroscopic properties of AlSi10Mg parts. Optical microscopy observations are carried out to link the microstructure to macroscopic properties.
Findings
Macroscopic properties of DMLS parts are influenced by the change in process parameters. There is a close correlation between the geometry of scan tracks and macroscopic properties of AlSi10Mg parts manufactured by DMLS process.
Originality/value
The knowledge of utilizing optimized process parameters is important to fabricate DMLS parts with better mechanical properties. The present research based on applying experimental design is the first analysis for AlSi10Mg parts produced in DMLS process.
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Elena Bassoli, Andrea Gatto and Luca Iuliano
Additive manufacturing is today a viable industrial solution alongside traditional processes. Techniques like selective laser sintering (SLS) address the issues of digital…
Abstract
Purpose
Additive manufacturing is today a viable industrial solution alongside traditional processes. Techniques like selective laser sintering (SLS) address the issues of digital production and mass customization in a variety of materials. Composite parts can be obtained with specific functional and mechanical properties. Building orientation during additive manufacturing often causes anisotropy of parts' properties that is still unspecified in technical information. The purpose of this paper is to investigate the mechanical performances and failure mechanisms of an aluminium‐filled polyamide and of a new alumina‐polyamide composite produced by SLS, in comparison with unfilled PA.
Design/methodology/approach
A specific focus is set on the evaluation of primary and secondary anisotropy in the case of metal or ceramic filler, as well as on the specific contribution of powder distribution modes and joining phenomena. Macroscopic mechanical tests and the observation of joining and failure micro‐mechanisms are integrated.
Findings
The results prove the absence of relevant anisotropy amongst specimens that are produced with the axis parallel to the plane of powder deposition. Samples whose axis is parallel to the growth direction Z, instead, reveal a significantly different response with respect to other orientations.
Originality/value
An original explanatory model is assumed and validated, based on an anisotropic distribution of the reinforcing particles during parts' production, which determines the efficacy of the strengthening mechanisms during crack propagation.
Details
Keywords
Andrea Gatto, Elena Bassoli, Lucia Denti, Luca Iuliano and Paolo Minetola
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…
Abstract
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.
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G. Berti, L. D'Angelo, A. Gatto and L. Iuliano
This paper aims to develop a deep characterization of PA‐Al2O3 composite for selective laser sintering (SLS). Tension test is used to determine main mechanical characteristics of…
Abstract
Purpose
This paper aims to develop a deep characterization of PA‐Al2O3 composite for selective laser sintering (SLS). Tension test is used to determine main mechanical characteristics of the material, both at room temperature and at 100°C. An accurate knowledge of the parts' performances as a function of the building orientation, is fundamental to understand the manufacturing anisotropy. Particular attention is dedicated to the joining and failure micromechanisms ruling the macroscopic characteristics, on the basis of the knowledge developed by the authors on SLS of both metal and polymeric powders.
Design/methodology/approach
Specimens have been built with different orientations in regard to powder deposition plane and laser path. Tension test is used to determine main mechanical characteristics of the material, both at room temperature and at 100°C. A particular attention is dedicated to the joining and failure micromechanisms ruling the macroscopic characteristics of the composite material by means of optical and scanning electron microscope (SEM) observations.
Findings
The sintered material shows an evident anisotropy in the growth direction (z‐axis), as well as it seems to be not sensitive to the sintering direction at room temperature (x, y, xy). At 100°C the effect of sintering direction becomes more evident and a different behaviour results considering x‐ and y‐direction, respectively. Accurate SEM characterization has been carried out to understand the effect of the manufacturing anisotropy on the mechanical performances, both in terms of additive construction and laser sintering strategy. The observation of the rupture surfaces showed that cracks originate from the external surface and propagate initially by the ductile failure of the polymeric matrix, up to the sudden fracture of the whole section.
Originality/value
Previous studies concerning polyamide charged parts confirm the importance of fabrication parameters and geometry on the final performances, due to anisotropic heat supply and transfer phenomena. The originality of the paper is in the investigation on both at room temperature and at 100°C. Moreover, a model is proposed where it is hypothesized that the layer‐by‐layer construction is only marginally responsible of the anisotropic behaviour of the material.