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ispartof: pages:335-340 ispartof: Procedia CIRP vol:113 pages:335-340 ispartof: 21st CIRP CONFERENCE ON ELECTRO PHYSICAL AND CHEMICAL MACHINING, ISEM XXI location:Zurich, Switzerland date:14 Jun - 17 Jun 2022 status: Published online

Aerosol Jet® Printing (AJ®P) is a relatively novel additive manufacturing technique, of the type direct writing, principally applied for printed electronics. Particularly, AJ®P has the ability to print various functional inks (conductive, dielectrics, biological solutions) at micro-scale resolution and on free-from substrates. This work investigates AJ®P to fabricate conductive patterns on stereolithography (SLA) samples towards the development of an innovative bioelectrical device for in-vitro dual bioreactor sensing. Silver nanoparticle (AgNPs) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) inks were both tested. Preliminary results show a low metal-polymer AgNPs-SLA interaction, revealing the presence of pores and cracks along with the printed pattern after thermal sintering, with no electrical resistance (R) detected. In contrast, the PEDOT:PSS ink reveals a good covering of the SLA samples, with R decreasing with the number of printed layers (from ~700 KΩ to ~60 Ω for 15 and 40 layers, respectively, on lines 1 cm long). However, using the PEDOT:PSS ink, the total printing time was ~45 minutes, hence not ideal for an industry-oriented vision. Therefore, a study on the optimization of the AgNPs-SLA sample interaction was carried out. SLA samples were coated with Parylene-C (ParC), and further treated with a low pressure plasma. The final results show excellent conductivity (R~2.40 Ω), with a printing time of ~5.5 minutes (7 layers), demonstrating the possibility to obtain a functional circuit. Eventually, the circuit was encapsulated with polydimethylsiloxane (PDMS) in order to avoid a release of Ag+ ions, potentially toxic in the medium culture. ispartof: pages:174-179 ispartof: Procedia CIRP vol:110 pages:174-179 ispartof: V Cirp Biomanufacturing location:Calabria, Italy date:22 Jun - 24 Jun 2022 status: Published online

© 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license. The tool wear in micro-EDM milling can be measured off-line intermittently to adjust the wear compensation factor and to guarantee the machining accuracy. However during milling of complex 3D cavities, the off-line tool wear compensation has to be done more often which negatively affects the duration of the overall machining cycle. A combined off-line and in-line adaptive tool wear compensation method is proposed and experimentally validated for a more efficient machining approach. The method minimizes the off-line compensation operations by maximizing the in-line compensation via real-time pulse counting to predict the tool wear. The factors affecting the performance of this combined method are also addressed, where the change of tool path pattern being the most important one. It can effectively be detected by in-situ pulse frequency monitoring and generally requires a change from in-line to off-line compensation to maintain the desired machining accuracy. ispartof: pages:656-661 ispartof: Procedia CIRP vol:42 pages:656-661 ispartof: 18th CIRP Conference on Electro Physical and Chemical Machining (ISEM) location:JAPAN, Univ Tokyo, Hongo Campus, Tokyo date:18 Apr - 22 Apr 2016 status: published

Technical ceramics have numerous application in the industrial and biomedical field because of material properties such as: high hardness, high Young’s modulus, chemical resistance and dimensional stability. These superior properties make it difficult to shape technical ceramics in a flexible and accurate way. By embedding an electrically conductive phase inside tough, hard and brittle non-conductive technical ceramics, e.g.: ZrO2, Al2O3 & SiC, it is possible to create ceramic blanks which can be processed by electro-chemical processes, such as Wire Electrical Discharge Machining (W-EDM). Till today, research on EDM machining of ceramic parts is often limited to the machining of small sized samples, mainly due to the fact that larger blanks are difficult to produce or not commercially available. Today, novel sintering techniques make it possible to create large fully dense ceramic composite blanks, allowing the production of bigger monolithic ceramic parts in a more cost effective manner. In the presented research, the effect of higher cutting dimensions on the Wire EDM performance is investigated. ZrO2-TiN blanks (diameter: 250 mm, height: 16 mm) made by hybrid plasma spark sintering are processed by W-EDM. Different finishing steps are used to obtain Ra roughness values below 0.5 μm, and for each finishing step a detailed analysis is made of the surface characteristics and material removal mechanism. The surface quality and material removal mechanisms are compared to findings in literature for small scale blanks. Beside melting and evaporation, other phenomena such as chemical decomposition and recast layers can be observed. Furthermore the effect of the finishing cuts on the bending strength is tested using 4 point bending setup and correlated to the surface roughness. Analysis from this research show that large scale ZrO2-TiN blanks are industry ready to be machined by W-EDM, hopefully bringing forward new applications. ispartof: pages:268-273 ispartof: 18th CIRP Conference on Electro Physical and Chemical Machining (ISEM XVIII) vol:47 pages:268-273 ispartof: 18th CIRP Conference on Electro Physical and Chemical Machining (ISEM) location:Tokyo, Japan date:18 Apr - 22 Apr 2016 status: published

The quasi-static mechanical properties of Fused Deposition Modelling ABS parts are largely influenced by the quality of the interconnection between adjacent tracks and layers. During the process, coalescence of the interconnection is obtained through the thermal energy, present in the deposited material. The obtained coalescence is therefore strongly dependent on the temperature of the material and is therefore influenced by many factors related to the production process. However, the process parameters influencing this thermal history are often not monitored. Furthermore, when printing large batches in a single build, it is very difficult to control the process such that the optimal thermal history is obtained at every location in the build. Moreover, a profound knowledge on the influence of the thermal history on the coalescence of the interconnection between adjacent tracks is still lacking. This research is therefore aimed at investigating the influence between the inter-layer cooling time, i.e. the time between de deposition of two consecutive layers, and the resulting quasi-static mechanical properties, because this the latter is an important factor contributing to the temperature of the material at the moment of deposition of the next layer. Uniaxial test samples are built considering the build orientation and the number of parts in the envelope, in order to influence this inter-layer cooling time. Tensile tests are performed and the fracture surfaces are investigated using digital microscopy. ispartof: pages:748-753 ispartof: Procedia CIRP vol:42 pages:748-753 ispartof: CIRP Conference on Electro Physical and Chemical Machining (ISEM XVIII) location:Tokyo, Japan date:18 Apr - 21 Apr 2016 status: published

The surface quality that results when replicating micro features is one of the most important process characteristics in micro injection moulding, and it constitutes a manufacturing constraint in applying the technique to a wider range of micro engineering applications. Moulding micro features with a high aspect ratio is a critical task, in particular when the feature width is small, due to a faster temperature decrease than in macro/meso scale cavities. In order to investigate the influence of the thermal diffusivity of the mould material in micro structured surfaces replication, in this paper two moulds, made respectively of tool steel and zirconia ceramic composite, have been used to replicate a micro structured surface. Micro Electrical Discharge Machining (μEDM) was employed to manufacture both the steel and the ceramic mould. The thermal diffusivity of the mould materials was measured in order to relate it to the degree of replication. Then, micro features were replicated via micro injection moulding, at the same controlled process conditions, and the replication degree was measured by means of an optical coordinate measurement machine. The results of the experimental tests display a sharp improvement of the quality of the micro structure replicated with the ceramic mould, that is when using a mould material with low thermal diffusivity. This effect, which is related to the ability of the material to delay the polymer skin solidification when the cavity is filled in, can be effectively exploit to enhance the capabilities of the current micro injection moulding technologies in manufacturing components with features characterized by higher complexity and aspect ratio.

This paper presents an initial study on the feasibility of machining zirconia ceramics in the hard state. A fully sintered Yttria stabilized tetragonal zirconia poly crystalline ceramic (Y-TZP) was used as work piece material and experiments were performed on a Mori Seiki turn-mill centre. PCD tools with small rake angle (0˚) and large nose radius (0.8 mm) were chosen for the experiments. The study on the influence of process parameters, such as depth of cut, feed and cutting speed (>300 m/min), on the surface quality and tool wear was approached by means of a mixed full factorial experimental design. Machined samples and process chips were also analysed by scanning electron microscope (SEM) to achieve a deep understanding of the occurring material removal mechanisms (MRM) and achievable surface quality; also the PCD inserts were inspected after usage. The findings show that surface roughness (Ra) values below 0.6 μm are easily achievable; the material removal mechanism is mainly based on a combined ductile-brittle material removal. Adhesion of work piece material to the tool is regarded as the most significant tool wear mechanism.

Technical ceramics are generally used in high demanding applications, e.g.: Zirconia (ZrO2) has an excellent fracture toughness but it is difficult to machine into complex shapes. Electrical Discharge Machining (EDM) is a valid option for hard materials, though this requires an electro-conductive work piece. In the presented work a large scale ZrO2 blank with a conductive secondary TiN phase is processed by Wire -EDM with different finishing regimes. 4 Point bending tests are conducted to check the final flexural strength as a consequence of the EDM process, and the integrity of the surface and subsurface is analyzed and discussed. ispartof: pages:179-182 ispartof: 3rd CIRP Conference on Surface Integrity (CIRP CSI) vol:45 pages:179-182 ispartof: CIRP Conference on Surface Integrity location:Charlotte, NC, USA date:8 Jun - 10 Jun 2016 status: published