Abstract
Miniaturization encourages the development of new manufacturing processes capable of fabricating features, like micro-channels, in order to use them for different applications, such as in fuel cells, heat exchangers, microfluidic devices and micro-electromechanical systems (MEMS). Many studies have been conducted on heat and fluid transfer in micro-channels, and they appeared significantly deviated from conventional theory, due to measurement errors and fabrication methods. The present research, in order to deal with this opportunity, is focused on a set of experiments in the micro-milling of channels made of aluminum, titanium alloys and stainless steel, varying parameters, such as spindle speed, depth of cut per pass (ap), channel depth (d), feed per tooth (fz) and coolant application. The experimental results were analyzed in terms of dimensional error, channel profile shape deviation from rectangular and surface quality (burr and roughness). The micro-milling process was capable of offering quality features required on the micro-channeled devices. Critical phenomena, like run-out, ploughing, minimum chip thickness and tool wear, were encountered as an explanation for the deviations in shape and for the surface quality of the micro-channels. The application of coolant and a low depth of cut per pass were significant to obtain better superficial quality features and a smaller dimensional error. In conclusion, the integration of superficial and geometrical features on the study of the quality of micro-channeled devices made of different metallic materials contributes to the understanding of the impact of calibrated cutting conditions in MEMS applications.
Highlights
In recent years, with the rapid progress in micro-electromechanical systems (MEMS), many micromachining methods have been developed to satisfy the increasing demand for fast, direct and mass manufacturing of meso- (100 μm–10 mm)/micro- (0.1–100 μm) devices, with high aspect ratios and superior surfaces [1,2]
The gathered results were analyzed by material and by observing the mean average roughness, mean burr formation evaluation, channel mean width and its percentage error deviation relative to the nominal size, channel depth and its percentage error deviation relative to the nominal size (50 or 100 μm) and the predominant profile shape resulting from the process
The mean burr was evaluated as 3.10 out of five, this being the depth of cut per pass and the coolant application being the most important factor to consider in order to minimize the top burr formation of the micro-channels (Figure 14)
Summary
With the rapid progress in micro-electromechanical systems (MEMS), many micromachining methods have been developed to satisfy the increasing demand for fast, direct and mass manufacturing of meso- (100 μm–10 mm)/micro- (0.1–100 μm) devices, with high aspect ratios and superior surfaces [1,2]. The interest in the use of micro-channel heat exchangers (MCHE) has arisen, as they play an important part in the field of energy, as they can tolerate higher operating pressure, providing a larger surface area per unit volume, which results in a more efficient heat transfer and, its smaller size. Fuel cells are devices made up of three segments, which interact together: anode, electrolyte and cathode. The results of these interactions are two reactions: fuel consumption and the creation of water/carbon dioxide, along with an electric current. Many researchers are currently developing microchannel heat-exchangers, reactors and separators as components for compact hydrogen generators for fuel cells [8]
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