28 research outputs found
Influence of mould thermal properties on the replication of micro parts via injection moulding
No full textThe 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
Validation of on-machine microfeatures volume measurement using micro EDM milling tool electrode as touch probe
No full textIn micro electrical discharge milling, process parameters have to be empirically calibrated in order to achieve high precision machining; to this end, on-machine measurement of the material removed is of paramount importance. The capability of electrical discharge machines in detecting electrical contacts between the electrodes can be exploited to perform dimensional measurements, using the tool electrode similarly to the touch probe in a coordinate measuring machine. In this work an investigation of the accuracy of the on-the-machine volume measurements in a micro electrical discharge milling setup is carried out and an evaluation of the error affecting on-machine measurements is provided
Effects of the cavity surface finishing on the polymer filling flow in micro injection moulding
No full textPrefazione a Miranda Ernesto, Il dramma a "tristo fine". Il pensiero tragico di G. Leopardi
No full textEnvironmentally clean micromilling of electron beam melted Ti6Al4V
No full textThe paper is aimed at evaluating the performances of Minimum Quantity Lubrication (MQL), dry cutting and cryogenic cooling when applied to the micro-milling of Ti6Al4V titanium alloy samples obtained by Additive Manufacturing (AM) using the Electron Beam Melting (EBM) technology. The micro-milling tests were carried out on a high precision 5-axis micro-milling center, at varying cutting speed and feed per tooth. The performances of the different lubrication/cooling strategies were analyzed in terms of surface integrity, namely surface topography, nano-hardness and sub-surface microstructural alterations, in order to prove the impact of clean cutting conditions when applied to micro-machining of a AM titanium alloy of biomedical interest. It is shown that dry cutting assures the same performances of MQL, representing then the most suitable option to decrease the environmental impact of the machining process. (C) 2016 Elsevier Ltd. All rights reserved
