A comparison of the machining performance of micro-EDM milling and sinking is proposed considering the fabrication of micro-channels with controlled sloped walls realized in a hardened steel workpiece. Adopting the fine-finishing machining regime for both micro-EDM techniques, the experimental results show that micro-EDM sinking is about 10 times faster than milling in the worst case, though a lack of accuracy in the final micro-features in the former case is detected due to not compensated tool wear. On the contrary, micro-EDM milling provides a better control of the micro-channel dimensions. Finally, a micro-filter mold for medical applications is machined in order to show the potential of the combination of both technologies.

Aluminum alloys offer many machining advantages, such as excellent machinability and finish degree, outstanding tool life, and good corrosion resistance. They also display an elevated thermal exchange and weight reduction, which lead to easier handling compared to steels and make them good candidates for applications in the automotive and aerospace industry and in the field of mould production. Despite these recognized features, the machining accuracy, in particular in the micro-electro discharge machining (micro-EDM) process, needs further improvement. Revealing the nature of the Al alloys in EDM machining, some papers report of resolidifying layers in Al alloys appearing after the EDM process and grain compositions hugely affecting surface roughness. In particular, it has been observed that a thin and strong insulating layer due to the oxidation of the aluminum workpiece after machining leads to frequent tool breakage. In practice, this makes the micro-EDM process harder when micro-tools are meant to be used. However, to the best of our knowledge, the investigation of micro-EDM process performances of Al-Mg has not yet been fully explored. In this work, micro-EDM Al-Mg machining is presented: different energy levels were tested to find the proper parameter combination feasible to process micro-features. The machining geometrical limits are also investigated, putting in relation the energy levels to different electrode tool diameters. The experimental results are discussed on the basis of the evaluation of material removal rate (MRR), tool wear ratio (TWR), surface roughness and sparking gap. The machining of a micro-shaft housing component featuring high aspect ratio (HAR) is also shown as demonstrator to prove the effectiveness of the micro-EDM parameters selected from the previous trials.

In the present paper, a numerical approach to model the layer-by-layer construction of cured material during the Additive Manufacturing (AM) process is proposed. The method is developed by a recursive mechanical finite element (FE) analysis and takes into account forces and pressures acting on the cured material during the process, in order to simulate the behavior and investigate the failure condition sources, which lead to defects in the final part geometry. The study is focused on the evaluation of the process capability Stereolithography (SLA), to build parts with challenging features in meso-micro scale without supports. Two test cases, a cantilever part and a bridge shape component, have been considered in order to evaluate the potentiality of the approach. Numerical models have been tuned by experimental test. The simulations are validated considering two test cases and briefly compared to the printed samples. Results show the potential of the approach adopted but also the difficulties on simulation settings.

The aim of the present study is the assessment of the integration of a low cost optical measurement device into a high-precision machine tool for micro manufacturing applications. The measurement system can be effectively integrated into the working volume of different types of machines allowing both tool and workpiece measurements and avoiding its disassembly from the machine stage for off-line measurements and, consequently, reference losses. The fast measurements of tool and workpiece during the machining contribute to increase the accuracy and reduce the overall machining-measurement iterations. The assessment is achieved by a test case where a low cost USB microscope is applied to a micro-EDM machine. The low cost device has been applied for tool electrode measurements and tool wear evaluation after an accuracy enhanced calibration procedure and high performance image processing algorithms, which effectively reduce the lack of the hardware performance. The measurement performance gives a feedback on the deviations of the machined features from nominal geometry and allows their compensations by an adequate machining strategy.

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.

The present paper reports the design and fabrication of a mould for mass production of a microfluidic device, "opticalstretcher lab-on-chip, a dual-beam optical trap that is used for trapping and deforming micrometer-sized particles.In particular, the mould is designed considering multiple and interchangeable inserts for realizing different microfeaturesadopting different processes. Microchannel, reservoirs and V-grooves have been machined viafemtosecond laser process due its capability to process large surface areas with relatively small depth features andhigh removal rate. On the contrary, complex 3D micro features with high aspect ratio for inverse capillary tubehousing have been manufactured via ?-electro-discharge-machining technology, since fine pulse discharges canbe used to ensure high precision and good surface roughness. Three-dimensional filling numerical analysis hasbeen also performed to improve the device design for the ?-injection moulding process and to set the optimizedprocess parameters. Several prototypes of the Lab-on-chip have been fabricated and experimental tests have beenperformed, showing the feasibility of this technological approach

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.

Microinjection moulding combined with the use of removable inserts is one of the most promising manufacturing processes for microfluidic devices, such as lab-on-chip, that have the potential to revolutionize the healthcare and diagnosis systems. In this work, we have designed, fabricated and tested a compact and disposable plastic optical stretcher. To produce the mould inserts, two micro manufacturing technologies have been used. Micro electro discharge machining (µEDM) was used to reproduce the inverse of the capillary tube connection characterized by elevated aspect ratio. The high accuracy of femtosecond laser micromachining (FLM) was exploited to manufacture the insert with perfectly aligned microfluidic channels and fibre slots, facilitating the final composition of the optical manipulation device. The optical stretcher operation was tested using microbeads and red blood cells solutions. The prototype presented in this work demonstrates the feasibility of this approach, which should guarantee real mass production of ready-to-use lab-on-chip devices.

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.

In this work, the implementation of an energetic model capable of predicting the energy consumption of a micro-electro discharge (micro-EDM) machine is presented. The developed model requires two main inputs: the estimate of the power absorbed by each subsystem composing the machine tool and the operation times, which includes the machining times. The power contributions can be determined via machine data sheets and via measurements. The energy consumption of a machine tool is due to two main contributions, ascribed to auxiliary units and to the manufacturing process itself. The developed model has been validated considering the micro-EDM milling of a circular pocket. The comparison between the estimated and measured energy consumption shows that the model is not only very accurate, but also very sensitive to the correct estimate of the machining times. Indeed, when the correction of the erosion time is operated by considering the actual value obtained by experiments instead of the one estimated by the CAD/CAM, the error referring to each energy contribution estimated by the model is greatly reduced. Furthermore, it can be noticed that most of the energy consumed by the micro-EDM manufacturing is actually inferable to the chiller unit.

The energetic model of a micro-EDM machine is presented. The model considers the energy required by the axis drivers, the micro-EDM generator, the air compressor and the chiller of the dielectric fluid. The model parameters have been experimentally identified during the micro-EDM machining of a blind hole. The resulting model is quite accurate and presents very small errors with respect to the actual energy used. However, the model is quite sensitive to the estimation of the machining time, which is provided by the CAD/CAM

The power spectral density (PSD) of the voltage and current waveforms acquired during micro-EDM millingexperiments are calculated and analyzed. The estimate of the PSD in the frequency domain allows to identify thepulse energy contribution in relation to the dynamics of the erosion process. The first results show that most of theenergy released by the micro-EDM generator in the sparking gap during the erosion process is concentrated at thefundamental frequency set by the end-user, which in turns means that the process is stable. However, thecontribution to the fundamental frequency is not provided by normal pulses only, but also by arcs. Nonetheless, arelevant number of unpredictable events (arcs and delayed occurrence) leads to several non-negligible subharmoniccontribution, which witnesses the presence of inductive currents generated during the erosion process.

In this paper, the pulse discrimination of gap voltage and discharge current waveforms occurring during micro-EDM milling of micro-channels is analyzed in relation to process parameters variation and machining performance. The pulse classification algorithm discriminates voltage and current waveforms into four defined pulse types: short, arc, delayed and normal. The micro-channels are manufactured in hardened steel using an energy level corresponding to the finishing regime and varying pulse width, frequency, gain and gap. The analysis shows that when the erosion process is stable, normal discharges are predominant. Delayed and short pulses are very sporadic. A major number of arcs can be detected when the gap is decreased and gain increased, i.e. erosion speed and feed rate are increased and affect in particular tool wear. Also the increase of the pulse width has an effect on tool wear, though the percentage of the arcs remains small. On the contrary, material removal rate does not seem to be apparently related to the percentage of arcs as the process parameters are varied, since these values are spread in a constant range for all parameter combinations. The evaluation of the depth errors does not provide any significant insights about the erosion process in relation to the considered process parameters.

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.

Since traditional handling mechanisms have an unpredictable behavior at micro scale, micro-assembly is a bottleneck in the development of hybrid micro-systems, and the development of new approaches is strongly demanded. In this paper, a recent study of the fabrication of a ceramics vacuum micro-gripper to handle parts in the range of hundreds of microns (300-1000) is presented. Among the possible micro manufacturing processes, micro-EDM has been selected as proving to be a very competitive fabrication technology for the manufacturing of ultra miniature components and micro sized features. The influence of the process parameters on the machining performance of interest is firstly investigated; then, the experimental results on machining the micro gripper are presented, finally concluding remarks are given.

Measuring 3D micro-features is a challenging task that is usually performed using high-cost systems generally based based on technologies with narrow working ranges and very accurate control of the sensor positions. Well-known image analysis methods, such as Photogrammetry, would likely lower the costs of 3D inspection of micro-features and add texture information to the 3D models; however, the behaviour of Photogrammetry is strongly affected by the scaling method because it retrieves a model that must be scaled after its computation. In this paper, an experimental study of the validity of a hybrid 3D image processing method for measuring micro-features is presented. This method exploits the Depth-from-Focus method to retrieve the correct scale for a photogrammetric model. The measurement of properly-designed and manufactured specimens was performed by following and adapting the German guideline VDI/VDE 2634, Part 3 to validate the method using calibrated specimens. The proposed system has been demonstrated to be very promising can achieve an error of less than 10 ?m.

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

In this paper, the influence of tool path variation on micro-EDM milling performance of square micro-cavities havingthree different fill factors (FF, ratio between electrode toolsection area and feature section area) is presented. Threecavities for each considered FF have been machined and theexperimental results have been evaluated in terms of materialremoval rate (MRR) and tool wear ratio (TWR). The analysisshow that the machining of the cavity with medium FF displaysa MRR which is unexpectedly smaller than the onemeasured for the smallest cavity. The reason of such resultshas been investigated by analyzing the influence of tool pathon working conditions. Hence, a new set of micro-cavities hasbeen machined varying the path lengths. The new resultsconfirmed that, in dependence on the FF and cavity depth(expressed in terms of aspect ratio, AR), the proper setting ofthe tool path lengths can significantly improve the machiningperformance, in particular, in terms of MRR.

Advanced engineering ceramics display excellent mechanical properties such as high hardness, highcompressive strength, chemical stability, wear and thermal shock resistance. Due to their superior performance overother materials, the use of ceramics in a range of different applications is increasing year by year. Bio-ceramics, such asalumina, zirconia, titania, Si3N4-TiN, just to mention a few, have been of interest for many years for orthopaedic anddental applications. However, a number of challenges in their application still remain, including improvements in thematerial properties (mechanical and 'bio-compatible' feasibilities) and in the manufacturing process chain toward thefinal product. Electrical Discharge Machining (EDM) can be successfully employed to machine complex 3D geometriesalso on hard materials exhibiting a brittle behaviour, such as ceramics, on the condition that the limit of their lowelectrical resistivity is overcome. To this aim, some ceramic composites are synthesized using second electroconductivephases comprising Titanium, resulting in ZrO2-TiN, Si3N4-TiN, B4C-TiB2. Moreover, when ceramic-basedscaffolds and prostheses are fabricated, this additional phase seems to have a good physiological impact on cell growthand proliferation. In this paper, micro-EDM manufacturing of different micro-textures for scaffold realization made onSi3N4-TiN is presented and discussed. Different experiments have been performed in order to define optimal micro-EDM electrical parameters in terms of material removal rate (MRR) and tool wear ratio (TWR). Micro-electrodes withdifferent diameters are used for different machining regimes, roughing, semi-finishing and finishing, with the goal ofidentifying minimum geometrical limits on micro-pins textures machining and also taking into account that highaveraged surface roughness is required for this application.

This paper discusses the applications and development of magnetic actuators for meso-scale mechanisms. Due to their small sizes, meso-scale parts cannot be actuated using techniques typical of macro-scale mechanisms, such as servos or ball screws. Similarly, the techniques used in micro-actuation, such as the use of electrostatic force in MEMS devices, cannot be easily scaled up to the meso-scale. As a result, the use of magnetic forces for actuating meso-scale mechanisms may be capable of filling this void of actuation methods.A case study of a fixturing mechanism meant for meso-scale end-milling was analyzed. This mechanism uses two fixed-fixed beams in order to actively tune the harmonic modes of the machining operation in order to improve the stability of the cutting. It also uses magnetic forces to actuate the fixturing platform in order to provide close-loop feedback of cutting force. This mechanism was then scaled down to create a meso-scale mechanism that can be used for a variety of purposes. It is possible that this research could have applications in biomedicine, where magnets can be used to remotely actuate clamping devices; consumer electronics, where it can provide added stability for devices such as digital video cameras; and small satellites, where it can be used to help prevent damage to fragile parts

This research is carried out to cover the gap in producing high-precision micro-components using SLM as well as to study the potential of using µ-EDM in the field of additive manufacturing. The process offers an optimized technique to manufacture high-quality micro implantable components with the highest density and the best surface finish

In spite of significant improvements in micro-replication techniques, methods to fabricate well-defined net shape microstructures are still in a developing stage. Soft lithography has the capability to manufacture complex micro- and nanostructures. Although it is considered a robust technique, a major limitation is related to the distortion encountered in the fabricated structures during the drying process. In the present work, a manufacturing technology has been developed that emerges the benefits of soft lithography and micro-electrical discharge machining (u-EDM) to produce stainless steel precise micro-components for micro-implantable devices. The micro-parts produced by soft lithography were subsequently surface processed via u-EDM in order to improve the surface quality. In addition to this, it was found that u-EDM drastically improved the surface roughness of stainless steel micro-components from Ra = 3.4 um to Ra = 0.43 um

Micro Electrical Discharge Machining (liEDM) technology is widely used to process conductive materials, regardless to their hardness and strength, and realize micro-sized feature components for industrial application. liEDM proves to be a very competitive fabrication technology since micro-sized features within 1 Lim of accuracy and with high surface quality (<0.1 Lim Ra) can be attained. When High Aspect Ratio (HAR) micro-features are machined via liEDM milling, the main problem is to identify the technological parameters and settings mainly affecting the process performance. In the present study the influence of the adjustment factor and flushing conditions are investigated and discussed for the machining of HAR cavities with different Fill Factor (FF). Material Removal Rate (MRR) and Tool Wear Ratio (TWR) are evaluated when deep cavities having variable square sections are machined on Ni-Cr-Mo steel workpiece. All tests are performed using a state of the art micro-EDM milling machine, with a Tungsten Carbide electrode tool and a dielectric oil for flushing. The experimental results presented here highlight different trends in the machining performance in dependence of AR and FF. In particular, MRR exhibits a decreasing trend where the curve slopes are strictly related to the FF and the initial adjustment factor. On the contrary,TWR, for higher FF, displays two distinct trends characterized by opposite slopes in each curve. Finally a nozzle for micro-injection with varying Aspect Ratio and Fill Factor is machined and presented as demonstrator.

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.

The fabrication of personalized implants, tailored on patient needs, is a key issue for the future of several surgical fields. The presence of a prototyping service inside the hospital would be an added value for improving clinical activity. In this context, micro-Electro Discharge Machining is exploited to customize fixation devices in orthopedic surgery. An overview of the main devices is carried out in order to identify the main characteristics and to define the common fixation system specifications. The experimentation includes a technological evaluation of the proper micro-EDM technology, chosen according to the final design of the components. Two materials are investigated for the device fabrication: titanium and Si3N4-TiN ceramic composite. An optimization of the main technological parameters is performed in order to maximize the material removal rate ensuring the accuracy of the micro-features required. Finally, a test case is selected in order to evaluate the entire fabrication process chain.

This presentation reports the comparison of the machining performance of micro-EDM milling and sinking for the fabrication of micro-channels with controlled sloped walls realized in a hardened steel workpiece. The machining regime used for both micro-EDM sinking and milling is the fine-finishing. The results show that micro-EDM sinking is about 9 times faster than milling, though the effects of tool wear become relevant inducing a lack of accuracy in the final micro-features. Despite the slower machining time, micro-EDM milling provides a better control of the micro-channel dimensions and draft angles of the walls. No difference related to surface roughness is detected, since the energy level used in both approaches is the same. A micro-filter for hearing aid, dialysis media and inhaler, having a diameter of 2.3 mm characterized by a grid of 76 micro-pins, is machined in order to show the potential of the combination of both technologies

This work deals with the investigation of the micro Electrical Discharge Machining (micro-EDM) behaviour of a commercially available ZrO2-TiN ceramic composite. The study is performed on an advanced engineering EDM equipment dedicated to micro EDM applications. Taguchi orthogonal array and one factor variation design are employed as investigation methodology for the understanding of the influence of the electrical parameters on the micromachining performance and its optimisation, respectively. The response is evaluated in terms of volumetric Material Removal Rate (MRR), Relative Tool Wear (RTW) and surface quality. Due to the importance that surface integrity has on the mechanical behaviour of ceramics during service, the study focuses on the semi-finishing/finishing regime. The material investigated displays MRR up to 0.22 mm3/min and RTW being in the range of ~ 5-15 %. Surface roughness lower than 0.2 ?m are achievable. Due to the ideal flexural strength and fracture toughness of ZrO2-TiN composites, a micro-aerodynamic thrust bearing surface is realized as application example.

This paper reports the comparison of the machining performance of micro-EDM milling and sinking for the fabrication of micro-channels with controlled sloped walls realized in a hardened steel workpiece. The machining regime used for both micro-EDM sinking and milling is the fine-finishing. The results show that micro-EDM sinking is about 9 times faster than milling, though the effects of tool wear become relevant inducing a lack of accuracy in the final micro-features. Despite the slower machining time, micro-EDM milling provides a better control of the micro-channel dimensions and draft angles of the walls. No difference related to surface roughness is detected, since the energy level used in both approaches is the same. A micro-filter for hearing aid, dialysis media and inhaler, having a diameter of 2.3 mm characterized by a grid of 76 micro-pins, is machined in order to show the potential of the combination of both technologies.

The mechanical behaviour of specimens fabricated using FDM machine has been thoroughly studied and several works have been presented. However, they are focused on few materials, in particular ABS, while very few papers analysed the mechanical properties of FDM samples made by PLA filament. Even though ABS is well known for its superior mechanical properties, some applications might require materials with other properties, such as PLA.Therefore, a deeper investigation of the effect of the process on its properties is needed. In this study, at first, the influence of the main FDM process parameters, such as raster angle, extrusion width, air gap and extrusion temperature, on mechanical performance of PLA samples has been evaluated. The mechanical tests have been carried out on miniaturized tensile specimens focusing on the tensile test main properties: ultimate tensile stress, Young modulus and elongation at break. Moreover, an experimental campaign has been carried out on the effect of a thermal post-processing, in order to evaluate the effects of the treatment and its relation with the process parameters on the mechanical properties of the specimens.

This paper addresses the production by micro Electrical Discharge Machining (EDM) milling ofceramics thrust bearing surfaces to be inserted in an air bearing unit for high speed (up to 500 krpm)turbomachinery applications. A ZrO2-TiN electrical conductive ceramic composite is here selected as structuralmaterial in order to fulfil the functional requirements of the component and allow its accurate and flexiblemachining via EDM. EDM experiments are firstly conducted towards the definition of suitable machiningconditions. The components are realized by applying a layer-by layer milling strategy. The surface quality andgeometrical accuracy are finally evaluated; the surface roughness obtained is 0.23 mm and the overall accuracy iswithin 2 mm.

Photogrammetry can be used for the measurement of small objects with micro-features, with good results, low costs, and thepossible addition of texture information to the 3D models. The performance of this technique is strongly affected by the scalingmethod, since it retrieves a model that must be scaled after its elaboration. In this paper, a fully automated multi-step scalingsystem is presented, which is based on machine vision algorithms for retrieving blurred areas. This method allows researchers tofind the correct scale factor for a photogrammetric micro model and is experimentally compared to the existing manual methodbasing on the German guideline VDI/VDE 2634, Part 3. The experimental tests are performed on millimeter-sized certifiedworkpieces, finding micrometric errors, when referred to reference measurements. As a consequence, the method is candidate tobe used for measurements of micro-features. The proposed tool improves the performance of the manual method by eliminatingoperator-dependent procedures. The software tool is available online as supplementary material and represents a powerful tool toface scaling issues of micro-photogrammetric activities.

In this paper, the study of the micro-EDM milling of 3D sloped pockets realized in Si3N4-TiN ceramic composite is reported. The goal of the analysis is the investigation of geometrical errors affecting the surface accuracy of inclined walls, characterized by different draft angles. Preliminary experiments have been performed using two different levels of energy and varying the layer thickness used to implement the layer-by-layer strategy. Also the number of electrical touches done to monitor tool wear rate and depth error during each erosion process has been changed. The experimental results obtained by the measurements performed directly on the micro-EDM milling machine show that most of the errors on the manufacturing of inclined surfaces are found in the first part of the erosion process. These errors are mainly due to: the number of touches (control number) and the proper initial setting of the parameter assigned to compensate tool wear, the adjustment factor. Morphological measurements performed using a 3D high precision conoscopic holography scanner have confirmed that the surfaces of the inclined walls suffer of some defects on the top of the pockets. However the surface profiles of the inclined walls are quite good and no step-like trends have been detected, suggesting that the layer thicknesses for all trials have been properly set. Moreover, the draft angles values are very close to the ideal ones

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.

The present study explores the design of an effective process chain that combines micro Abrasive Waterjet (micro-AWJ) and micro Wire Electro Discharge Machining (micro-WEDM) technologies. An experimental spring component is chosen as leading test case, since fine geometric features machining and low roughness on the cut walls are required. The advantages deriving from the two technologies combination are discussed in terms of machining time, surface roughness and feature accuracy. First, the performance of both processes are assessed by experimentation and discussed. Successively, different process chains are conceived for realizing two test cases with different size, displaying the advantages and drawbacks of the combinations.

In this paper, gap voltage and discharge current waveforms occurring during micro-EDM milling of micro-channels realized in a Si3N4-TiN workpiece are monitored and discriminated. The analysis is performed by implementing a design of experiment for the identification of the relationship existing among process parameters, machining performance and pulse type distribution. A pulse classification algorithm gathers gap voltage and current waveforms into four defined pulse types: short, arc, delayed and normal. The micro-channels are manufactured using an energy level corresponding to the finishing regime and varying pulse width, frequency and gap. The results show that material removal rate (MRR) benefits from the increase of normal and delayed pulses as expected. However, also arcs seems to increase MRR. Tool wear ratio (TWR) grows when normal pulses increases, whilst no particular influence is observed by delayed pulses. The peculiarity in TWR is found when arcs are considered: the values slightly decreases when arcs are more frequent, according to MRR behavior, but on the contrary with previous analysis done on different workpiece materials. This issue is currently under investigation

This paper discusses the performance of micro-electro-discharge machining (micro-EDM) process using different flushing media. Several tests have been performed considering a hardened steel thin workpiece machined via micro-EDM drilling and through-trench and different flushing fluids: deionized water, tap water, deionized water with Garnet, tap water with Garnet. Garnet is the abrasive material exploited in the micro-AWJ and the concentration per liter of water considered in micro-EDM experiments is the same as required in micro-abrasive water jet (micro-AWJ) machining. A customized system has been built on micro-EDM Sarix SX 200 HP machine to allow the water-based fluid refill and liquid level monitoring during the experiments. The micro-EDM trials have been carried out considering two machining regimes, roughing and semi finishing. The different water-based fluids have different electrical conductivities, which lead to different machining performance. Material removal rate (MRR) and tool wear ratio (TWR) have been estimated in terms of average and standard deviation. The results show that the presence of Garnet does not affect MRR consistently, since the particles do not play an active role in the erosion process but affect surface quality, as proved by the inspection of crater morphology and dimensions estimation performed via confocal microscope. For the considered experiments, MRR is generally increased as the conductivity decreases, in particular when semi-finishing regime is used. Also TWR decreases dramatically with the use of water-based fluids, since a protective recast layer is also deposited on the tool tip preventing wearing. Our analysis shows that micro-EDM can be successfully performed using the same liquid (water and abrasive) used in micro-AWJ, and so paves the way towards the implementation of a hybrid process based on micro-AWJ and micro-EDM technologies.

Micro-manufacturing emerged in the last years as a new engineering area with the potential of increasing peoples' quality of life through the production of innovative micro-devices to be used, for example, in the biomedical, micro-electronics or telecommunication sectors. The possibility to decrease the energy consumption makes the micro-manufacturing extremely appealing in terms of environmental protection. However, despite this common belief that the micro-scale implies a higher sustainability compared to traditional manufacturing processes, recent research shows that some factors can make micro-manufacturing processes not as sustainable as expected. In particular, the use of rare raw materials and the need of higher purity of processes, to preserve product quality and manufacturing equipment, can be a source for additional environmental burden and process costs. Consequently, research is needed to optimize micro-manufacturing processes in order to guarantee the minimum consumption of raw materials, consumables and energy. In this paper, the experimental results obtained by the micro-electrical discharge machining (micro-EDM) of micro-channels made on Ni-Cr-Mo steel is reported. The aim of such investigation is to shed a light on the relation and dependence between the material removal process, identified in the evaluation of material removal rate (MRR) and tool wear ratio (TWR), and some of the most important technological parameters (i.e., open voltage, discharge current, pulse width and frequency), in order to experimentally quantify the material waste produced and optimize the technological process in order to decrease it.