In the last decades, metallic foams found commercial and industrial interests, thanks to their physical properties combined with good mechanical characteristics. Metal foam structures are very light and they can be used to reduce the weight of machinery without compromise the mechanical behavior. In this work, a study of the direct junction of metal foam with metal massive components was carried outbecause in literature there are few references to the formation of an intermetallic phase between aluminum foams and massive metal shells. Aluminium foams were manufactured starting from commercial foamable precursors: first of all, attention was paid to the repeatability of foaming process. Then, a direct connection between the foamed samples and the steel shell elements was pursued. The materials that seemed to facilitate the formation of an intermetallic layer were studied and the geometry of the steel mould and the most useful way to place the precursor in the steel mould and then in the furnace were considered. To evaluate the produced aluminum foam, morphological and mechanical characterizations were done. Results showed that, keeping constant the contour conditions, it was possible to control the process and a first result, in term of interaction between foam and mould, was obtained using an X210Cr12 steel as mould material. The SEM observation revealed the presence of an intermetallic phase between the two different materials.

In this study the Taguchi method is used to find the optimal process parameters for aluminium foammanufacturing. Porous metals are the unique materials used for light weight structural components, for filters andelectrodes and for shock or sound absorbing products. Recently, interesting foaming technology developments haveproposed metallic foams as a valid commercial chance. Metallic foam manufacturing techniques include solid statepowder methods, gas blowing processes, metal deposition onto a polymer precursor and liquid state processing.The aluminium foams presented in this study are produced by the powder metallurgy route starting fromaluminium powders with titanium hydride as the foaming agent. During the experimental work, many samples aremade by utilizing the combination of process parameters based on Taguchi orthogonal design. Three manufacturingparameters are studied: the silicon carbide content in powder mixture, the compaction pressure and the foamingtemperature. The Taguchi method is applied to design an orthogonal experimental array and a multi-objectiveoptimization approach is then proposed by simultaneously minimizing the relative density and maximizing theabsorbed energy. Verification test is also performed to prove the effectiveness of the presented technique.

In questo lavoro sono stat e studiate le relazioni esistenti tra le condizioni di processo, la struttura e leproprietà di provini ottenuti mediante la tecnologia di micro-stampaggio a iniezione. I micro-provini consistono in"dog-bone" di dimensioni molto contenute in poliossimetilene (POM), che è un polimero semi-cristallino largamente impiegato per la realizzazione di componenti meccanici per le ottime caratteristiche meccaniche, la stabilità all'umiditàe la buona lavorabilità. In particolare, sono state ricercate le correlazioni tra le temperature di processo (temperatura del fuso polimerico e dello stampo), le caratteristiche microstrutturali del materiale e le proprietà meccaniche dei micro-manufatti. I risultati mostrano che in funzione delle temperature di processo impiegate, si ottengono microstrutture caratterizzate da diversi livelli di orientazione dei domini cristallini di POM; le differenze sono tali da riflettersi sul comportamento meccanico dei micro-provini.

This paper reports on design, fabrication, and characterization of a microfilter to be used in biomedical applications. The microfilter, with mesh of 80 ?m, is fabricated by micro-injection molding process in polymeric material (polyoxymethylene (POM)) using a steel mold manufactured by micro-electrical discharge machining process. The characteristics of the filter are investigated by numerical simulation in order to define a suitable geometry for micro-injection molding. Then, different process configurations of parameters (melt temperature, injection velocity, mold temperature, holding pressure and time, cooling time, pressure limit) are tested in order to obtain the complete part filling via micro-injection molding process preventing any defects. Finally, the component is dimensionally characterized and the process parameters optimized to obtain the maximum filtration capacity.

This paper reports on design, fabrication and characterization of a micro-filter for hearing aid, dialysis media and inhaler. The microfilter is fabricated by micro injection moulding process in polymeric material (Polyoxymethilene - POM) using a steel mould manufactured by micro electrical discharge machining process. A novel filter configuration is proposed and, in the design step, the characteristics of the filter are investigated by numerical simulation in order to define a suitable geometry for micro-injection moulding. Then, different process configuration of parameters (melt and mould temperature, injection velocity, holding time and pressure, cooling time, pressure limit) are tested in order to obtain the complete part filling. Finally the component is dimensionally characterized and the process parameters optimized to obtain the maximum filtration capacity.

Due to the sensitive nature of applications of the micro injection moulding process, such as medical and aerospace, achieving high quality parts with high dimensional accuracy is crucial. In this work, simulation and an experimental study was performed to analyse the effect of four main parameters (melt and mould temperature, injection speed and holding pressure) on dimensional accuracy of a micro feature. Moreover, the focus was also to assess the process capability of a screwless/two plungers micro moulding machine in processing polyoximethilene (POM) and liquid crystal polymers (LCP). Results showed that mould temperature and injection speed was the most effective on dimensional accuracy respectively for POM and LCP and high settings for all the parameters improved the accuracy of the ribs. For LCP achieving process reproducibility was more difficult than POM even if the obtained dimensional errors are considerably lower.

Metal foams are conquering an increasing interest in the industrial stage. Aluminium foams have ahigh potential for use in weight-sensitive construction parts. The stiffness to weight ratio is themain criteria for material selection in light-weight design. Many processes are available tomanufacture metal foams classified according to the state in which the metal is processed (liquid,solid, vapour or a solution of metal ions) and similarly different techniques can be applied to jointhe foam to bulk elements. In this context, the aim of this work is to perform an experimentalstudy of laser welding for realising parts with an aluminium foam core (AlSi10 and AlSi0.6Mg1) anda steel external skin. The goal of the paper is to point out the feasibility of the process with theformation of an intermetallic phase between steel and aluminium and then the influence of themain process parameters. The experimentation was carried out in two steps: a preliminary studyabout an overlapped joint between steel and foam sheets and then the joining of steel hollowprofile and aluminium foam obtained by a precursor material foamed directly inside the profile. A fullfactorial plan was designed by varying different process parameters referred to the laser (power ofthe laser source, execution speed, heat input and focal distance of the laser beam) while, exceptthe precursor material, all the factors relative to the foam were kept constant. As results anintermetallic phase formation between aluminium foams and a stainless steel sheets and mouldshave been obtained observed by micrograph examination.

In this work, aluminium foams produced by the powder metallurgy route are evaluated. This kind of aluminium foams have a high potential in weight-sensitive construction parts. The aim of this study is to evaluate the properties (in terms of foam morphology and plateau stress) and to optimize three control factors chosen: temperature, precursor material and mean of cooling. AlSi10 and AlSi0.6Mg1commercial foamable precursors are the starting materials. Different set of samples are realized following the DoE approach; manufactured samples have been morphologically and mechanically analyzed to evaluate what level of each parameter better influences the final quality of the foam. Temperature and mean of cooling have a great influenceon the mechanical behavior of the foamed structure.

Due to its ability to produce low-cost and high repeatable micro polymeric parts, injection moulding of micro components is emerging as one of the most promising enabling technologies for the manufacturing of polymeric micro-parts in in many different fields, from IT to Healthcare, to Medicine. However, when approaching the micro-scale, different issues related to the process should be addressed, especially as the depth of the mould cavity becomes very thin. In particular, the mould roughness could affect the surface quality of the produced micro components, like in macro moulding, as well as the complete filling of the parts. Although micro-injection moulding process has been extensively studied, further research on the effect of mould roughness conditions and on non-Newtonian fluid flow in micro-cavities are required. This will shed a light and open up new paths for a deeper understanding of the moulding scenario. The main objective of the present paper is the evaluation of the influence of the mould roughness on the polymer flow during micro injection moulding process. The test parts have been realized in POM material and have thickness lower than 250 ?m. The test part design has been properly conceived in order to neglect the effect of dimensions and geometry and to highlight the roughness contribution during the filling phase of micro injection moulding process. The experimentation has been performed considering cavities with different roughness values (3 levels) and decreasing depths (3 levels), for a total of nine test parts manufactured by micro-electrical discharge machining process (?-EDM). The results of the experiments are discussed in the paper and show that cavity surface roughness affects the injection process as the moulding scale level is decreased. In particular, when the cavity depths are reduced, higher surface roughness promotes the filling of components and this finding could be ascribed to the increase of wall slip effect.

Nowadays, the study of polymer nanocomposites is an active area of materials development because nanofillers and in particular Multi-Wall Carbon Nanotubes (MWCNTs) can significantly improve or adjust the properties of the materials into which they were incorporated such as optical, electrical, mechanical and thermal properties. MWCNTs have been adopted in quite a number of applications, but advancements in their properties are needed for spreading their potential. Moreover their behaviour and filling properties in micro injection moulding process have still to be studied.Therefore, in this work, experimental and statistical studies were performed to analyze the parameters effect on replicating capability of micro parts manufactured in POM/MWCNT by micro injection moulding process. Two compounds with different filler fraction (3 and 6 wt%) were tested and processed with different conditions and their operating range have been pointed out and compared with that of pristine POM (PolyOxyMethilene).The results show that the filler content has the effect to change slightly the operative range of the micro injection process parameters and to increase the replicating capability. The most effective parameters on replicating capability of micro ribs, evaluated by a dimensional index, are the mould temperature for the POM/MWCNT 3% and injection velocity for the 6% filler fraction.

The increasing demand for small and even micro scale parts is boosting the development of reliable micro system technologies. Micro-fabrication process capabilities should expand to encompass a wider range of materials and geometric forms, by defining processes and related process chains that can satisfy the specific functional and technical requirements of new emerging multi-material products, and ensure the compatibility of materials and processing technologies throughout these manufacturing chains. Micro injection moulding is the process of transferring the micron or even submicron precision of microstructured metallic moulds to a polymeric products. It represents one of the key technologies for micro manufacturing because its mass production capability and relatively low production cost. Polymers have relatively low cost, and offer good mechanical and thermal strength, electrical insulation, optical transparency, chemical stability and biocompatibility.In this work the authors investigate the micro injection moulding process parameters on the overall quality of a miniaturized dog-bone shaped specimen. The aim of the experimentation is to calibrate the process and set the machine for the correct filling of the component. A set of injection parameters are selected for study by experimental plan and simulation tool and then discussed. Simulation results are used to better understand the polymer flow behaviour during the filling phase. A commercial software is used and input data, collected during the micro injection moulding process, are included using as performance indicators flow front position and moulded mass. Process simulation can provide, at the present time, mostly qualitative input to the designer and process engineer. Two different polymers materials are tested and evaluated in relation to the process replication capability: Polyoxymethylene (POM) and Liquid Cristal Polymer (LCP). Finally, the moulding factors with significant statistical effects are identified. The holding pressure and holding time for POM and the holding pressure and injection velocity for LCP show the highest influence on achieving high part mass.

Due to its ability to produce low-cost and high repeatable micro-polymeric parts, micro-injection molding is emerging as one of the most promising enabling technologies in many different fields. When approaching the micro-scale, different issues related to the process should be addressed, especially as the thickness of the cavities becomes very thin. In particular, the mold roughness affects the surface quality of the micro-components produced, like in macro-molding, but this could also encompass the complete filling of the parts. The main objective of the present paper is to evaluate the roughness influence of the mold on the non-Newtonian fluid flow during the micro-injection process in thin micro-cavities where the mold surface condition could affect the process due to the phenomena neglected in macro- or mesoscale as less important boundary conditions. The part design was properly conceived in order to neglect the effect of dimensions and geometry and to highlight the roughness contribution during the filling phase. The experimentation was performed using cavities with different roughness values and decreasing depths from 200 to 50 ?m, considerably lower than 250 ?m found in literature and manufactured by the micro-electrical discharge machining (?-EDM). The results of the experiments are discussed and show that cavity-surface roughness affects the process as the molding scale is decreased. In particular, in thin cavities, higher surface roughness promotes the filling of component.

Injection molding of micro components is more and more an emerging technology for its ability to manufacture low cost and high repeatable micro polymeric parts relevant to many different fields, from IT to healthcare, to medicine. In particular, micro injection molding of thin cavities is an interesting challenge due to the large surface to volume ratio that characterizes the process. This condition emphasizes the heat transfer at the polymer/mold interface, especially when the depth of the mold cavity becomes very thin. Furthermore, the boundary conditions, neglected in macro scale, affect the process and hence the mold surfaces show high influence during products filling and not only on their final quality. Thus, the mold roughness should be considered in evaluating the polymer flow behaviour in filling micro thin cavities. In this work, three inserts were designed to evaluate roughness contribution during molding and were manufactured by micro electrical discharge machining process obtaining three thin cavities (depth of 100µm and different roughness values). These inserts were used for molding polymeric micro plates and the flow lengths, reached inside these parts, were measured as process quality response. The results show that the cavity roughness affects the micro injection process favouring the filling of the thin cavities. In fact, the samples, molded with the insert having the highest roughness, show the longest flow length. Finally, wettability measurements were performed on the mold inserts and also these results sustain the occurred relation suggesting a decrease of the heat transfer in the process at the increase of mold surface roughness.

Injection moulding of micro components is becoming more and more important for applications of micro system technologies in different fields (IT, Healthcare, Medicine) due to its ability to produce low-cost and high repeatable micro polymeric parts. However, when approaching micro scale level, different issues related to the process should be addressed, especially as the depth of the mould cavity becomes very thin. In particular, the mould roughness could affect not only the surface quality of the produced micro components, like in macro moulding, but also the complete filling of the moulded parts. This work aims to identify experimentally the effect of the roughness of thin mould cavity on filling capability in micro injection moulding process. Preliminary results of the experiments, carried out using POM material, are discussed in the paper and show that the surface roughness favours filling of the micro cavity.

The large surface area to volume ratio that characterized the micro injection molding process makes interfacial phenomena particularly critical and fundamental for the overall effectiveness of the process. This is more evident for micro injection molding of thinner part, where the roughness is comparable to at least one between the overall dimensions of the cavity. In this case, the contact situation between polymer and mold, significantly affects the heat transfer at interface, which strongly influences the polymer flow behavior. Therefore, in this paper, the effects of the polymer-tool interface on polymer flow were investigated. In particular, the filling of a representative micro part with a thickness of 100 ?m was studied as a function of surface roughness and mold wettability

Micro injection moulding process represents a key technology for realizing micro components and micro devices used in several fields: IT components, biomedical and medical products, automotive industry, telecommunication area and aerospace. The development of new micro parts is highly dependent on manufacturing systems that can reliably and economically produce micro components in large quantities. In this work the authors investigate the process parameters on the overall quality of a miniaturized dog-bone shaped specimen. The factors affecting micro flow behavior and components mass were studied byexperimentation (designed using DoE methodology) and simulation tool and then discussed. Different polymer materials, particularly indicated for the injection molding applications due to their flowability and stability, are tested and evaluated in relation to the process replication capability.It has been found that the holding pressure and holding time for Polyoxymethylene (POM) and holding pressure and injection velocity for Liquid Cristal Polymer (LCP) have the higher influence on achieving high part mass.

The increasing demand for small and cheap parts is boosting the development of reliable micro-system technologies. Fabrication process capabilities should expand to encompass a wider range of materials and geometric forms, which can satisfy the specific requirements of new emerging micro-products, and ensure the compatibility of new materials and processing technologies. Polymeric composites are very promising materials, since they offer new combinations of properties not available in traditional homogeneous materials. Because of their advantageous light weight, high strength, fatigue life, and corrosion resistance, they are forecast to replace conventional materials in several applications. Among the plastic process technologies, injection moulding is one of the key technologies for manufacturing miniaturised components due to its mass production capability and relatively low production cost. Micro-injection moulding allows to transfer micron and even submicron precision features to small products. Since final product properties strongly depend on materials and production processes and parameters, the process conditions of compounding as well as of product manufacturing have to be carefully studied and controlled. This is particularly important for the manufacturing of micro-products, since, at the micro-scale, some phenomena negligible at the macro-scale (as hesitation effect or capillarity forces for examples) can become important. However, only few studies concern the micro-injection of nanocomposites. Therefore, in this paper the micro-injection of two composites made of polyoxymethylene and carbon nanotubes has been studied. First, the electrical properties of the compounds have been measured; the fillers are dispersed in the matrix and form a network that dramatically increases the conductivity of the composites in comparison with the pristine resin. Then the compounds have been injected using a micro-injection machine and the components have been analysed. The mechanical analysis, based on tensile tests and dynamic-mechanical experiments on miniaturised dog-bone specimens, shows a slight reinforcing effect of the filler; however, the ductility is considerably reduced. This is likely due to a scarce adhesion of the carbon nanotubes and the polymer and the presence of some agglomerates. Moreover, as expected, the mould temperature affects the mechanical properties of the specimens, probably due to its effect on the internal structure of the solidified materials. The dimensional analyses carried out on micro-rib specimens show that replication capability is increased by the presence of the filler and using high values of the process parameters. Finally, microscopic analyses have been done in order to verify the dispersion and orientation of the fillers in the compounds. These effects have been observed only when high shear rates are involved.

Micro components and micro devices are strongly used in several fields: IT components, biomedical and medical products, automotive industry, telecommunication area and aerospace. A micro component is characterized by small dimensions of the product itself or small dimensions of the functional features. The development of new micro parts is highly dependent on manufacturing systems that can reliably and economically produce micro components in large quantities. In this context, micro-electrical discharge machining (EDM) for mould production and micro-injection moulding of polymer materials are the key technologies for micro manufacturing. This paper will focus on the production and quality evaluation of polymeric micro components manufactured by micro injection moulding. In particular the authors want to investigate the process parameters on the overall quality of the product. The factors affecting micro flow behavior, components weights and dimension definition are experimentally studied basing on DoE approach and then discussed.

Due to its high efficiency for the large scale production of polymeric parts, micro injection moulding is one of the key technologies of the new millennium. Although a lot of researches have been conducted to identify the most effective processing conditions for micro injection moulding, the comprehension of the influence of all parameters on the quality, the properties and the reliability of the moulded parts is still an issue. In this context, this study aims to evaluate the effects of the micro injection moulding process conditions on the tensile properties of micro parts, investigating the influence of three main process parameters: the injection speed, the mould temperature and the melt temperature. A full factorial plan has been applied to study the contributions of these parameters and a second study has been performed to understand the synergic interaction between the two temperatures on the tensile strength. Due to its high level of potential crystallinity, a typical semi-crystalline thermoplastic resin was used in the experiments. The results of the analysis showed a great influence of the mould temperature (T mould) on the ultimate tensile strength and of the melt temperature (T melt) on the deformation at the point of breaking; whereas the injection speed was significant on the overall mechanical performance. A new studied factor (T melt-T mould) could affect the resulting molecular structure and consequently the mechanical behaviour, but itself is not sufficient to thoroughly explain the observed behaviour. Moreover, the visual inspection of the deformation mechanism at break shows three distinctive trends demonstrating the great variability of the mechanical properties of micro-injected specimens due to process conditions.

Many research efforts have gone in the production of carbon nanotubes (CNT) composites for functional and structural applications and many processing methodologies have been experimented. Twin-screw extrusion appears to be the most suitable way from the perspective of production scale up and commercialization of these composites. At the same time, micro-injection molding process is considered as the key manufacturing technology for the mass production of miniaturized components and devices. Despite the massive literature about nanocomposites and microinjection molding process, few articles focus on the interaction between the compounding process and the following micro-injection molding transformation processes. This article aims at analyzing the influence of the screw configuration used in compounding process on the rheological and technological properties of the resulting nanocomposites. Two different combinations of screw elements have been tested to incorporate CNTs in two different resins: LCP (liquid crystal polymer) and POM (polyoxymethylene) typically used in micro-injection molding. The effects of the process set up have been observed studying first the rheology and then the moldability of nano-compounds microinjected ribs with high aspect ratio. The nanofiller dispersion has been evaluated via light and transmission electron microscopy. The results confirm that, the screws show different capacity at promoting the dispersion of the nanofiller, which affects the moldability of micro-injected CNT nanocomposites. The viscosity of the polymer seems a critical factor as well, because it influences first the dispersion of CNT bundle during extrusion and then the injection moldability of the composites in the micro-channels. POLYM. COMPOS., 38:349-362, 2017. © 2015 Society of Plastics Engineers. © 2015 Society of Plastics Engineers

Injection moulding of micro-featured plastic parts is becoming more and more important for applications of micro system technologies in different fields (IT, healthcare, medicine) due to its capacity to produce low-cost and high repeatable micro polymeric parts. However, approaching the micro world, different issues related to the process should be addressed, especially as the depth of the mould cavity becomes very thin. In particular, the characteristics of mould surface could affect not only the surface quality of micro components, but also the filling of injected parts. This work aims to identify the effect of the superficial texture on the filling capability of thin cavity in micro injection moulding process, and to evaluate the influence when the texture is obtained by different machining processes. The results of the experiments, carried out using a polymeric material, are discussed in the paper and show that, when the surface has an isotropic texture, the filling is proportional to the increase of the surface roughness, whereas an oriented direction of the texture longitudinal to the flow front favours the injection process.

Micro-injection moulding is becoming increasingly important among the available proc-esses for production of micro-electromechanical systems (MEMS) and microsystem tech-nologies (MSTs), and higher number of polymer products is being manufactured by thisprocess. Due to the sensitive nature of applications of this process, such as medical andaerospace applications, achieving high quality parts with high dimensional accuracy iscrucial. In this work, a design of experiment (DoE) approach is used. The aim is to studythe effects of three process parameters which are commonly used for research in this do-main, on the dimensional accuracy of microchannels with different sizes; they are injec-tion velocity, injection pressure, and melt temperature. The study focuses on twopolymers, polyoxymethylene (POM) and liquid crystal polymer (LCP). Experimentalresults showed that higher melt temperature and injection pressure resulted in higherdimensional accuracy. Nevertheless, high settings for the three parameters resulted inhigher percentage of flash in most cases. In conclusion, the most influential factors wereshown to be melt temperature and injection pressure.

Micro-injection moulding is one of the key manufacturing technologies for thermoplastic polymeric materials for the mass production of high value miniaturized components. However, this process is not just a straightforward down scaling of the conventional injection moulding technique. Indeed, during the micro-injection the polymer melt is forced to flow at high strain rates through very small channels in nonisothermal conditions; this can lead to complex microstructures and to parts with unexpected performances. In this work, the relationships among the processing conditions, the mechanical properties and the microstructural characteristics of polyoxymethylene miniaturized specimens obtained by injection moulding were investigated. The attention was focused on the influence of the process temperatures on the mechanical behavior, examined by uniaxial tensile tests, and on the microstructural characteristics of the specimens, examined by differential scanning calorimetry, wide-angle X-ray diffraction, polarized light microscopy, and dynamic-mechanical thermal analysis. The results highlighted that material ductility in the miniaturized specimens is significantly affected by the mould temperature, because of the sample microstructure. Different degrees of orientation of polymer crystallites and different morphologies of the skin/core transition region were observed in dependence on the process temperatures.

Achieving high quality parts is a crucial task for the micro injection moulding process due to the sensitive nature of applications as medical and aerospace. In this work, simulation and an experimental study are performed to analyse the effect of four main parameters (injection speed, melt and mould temperature, and holding pressure) on replicating capability of a micro feature by injection moulding process that is the main focus of the present paper. This work also assesses the performance of a screwless-two plungers micro moulding machine in processing polyoximethilene (POM) and liquid crystal polymers (LCP). Results show that mould temperature and injection speed are the most effective parameters on replicating capability respectively for {POM} and {LCP} and high parameters setting improved the dimensions of the feature and thus the quality. For LCP, achieving process reproducibility is more difficult than for {POM} even if the obtained replication fidelity is considerably higher.

Micro injection moulding process represents a key technology for realizing micro components and micro devices used in several fields: IT components, biomedical and medical products, automotive industry, telecommunication area and aerospace. The development of new micro parts is highly dependent on manufacturing systems that can reliably and economically produce micro components in large quantities. In this work, the authors investigate the process parameters on the overall quality of a miniaturised dog-bone-shaped specimen in order to determine the process constraints. The factors affecting parts aspects and mass are studied by experimentation designed using DoE methodology and then discussed. Two polymer materials (polyoxymethylene and liquid crystal polymer), particularly suitable for injection moulding applications due to their flowability and stability, are tested and evaluated in relation to the process replication capability. It has been found that the holding pressure and holding time for POM and holding pressure and injection velocity for LCP have the highest influence on achieving high part mass. Differently, melt temperature has the highest influence on minimising the process variability for both tested polymers. A further investigation has been carried out on the relationship between the holding pressure and the part mass and dimensions demonstrating the existence of a linear correlation between specimens mass and dimensions.