3,017 research outputs found
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Development of an electrochemical micromachining (μECM) machine
This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London.Electrochemical machining (ECM) and especially electrochemical micromachining
(μECM) became an attractive area of research due to the fact that this process does not
create any defective layer after machining and that there is a growing demand for better
surface integrity on different micro applications such as microfluidics systems and stressfree
drilled holes in the automotive and aerospace sectors. Electrochemical machining is considered as a non-conventional machining process based on the phenomenon of electrolysis. This process requires maintaining a small gap - the interelectrode gap (IEG) - between the anode (workpiece) and the cathode (tool-electrode)
in order to achieve acceptable machining results (i.e. accuracy, high aspect ratio with appropriate material removal rate and efficiency). This work presents the design of a next generation μECM machine for the automotive, aerospace, medical and metrology sectors. It has 3 axes of motion (X, Y and Z) and a spindle
allowing the tool-electrode to rotate during machining. The linear slides for each axis use air bearings with linear DC brushless motors and 2nmresolution encoders for ultra-precise motion. The control system is based on the Power PMAC motion controller from Delta Tau. The electrolyte tank is located at the rear of the
machine and allows the electrolyte to be changed quickly. A pulse power supply unit (PSU) and a special control algorithm have been implemented. The pulse power supply provides not only ultra-short pulses (50ns), but also plus and minus biases as well as a polarity switching functionality. It fulfils the requirements of tool
preparation with reversed ECM on the machine. Moreover, the PSU is equipped with an ultrafast over current protection which prevents the tool-electrode from being damaged in case of short-circuits.
Two different process control algorithms were made: one is fuzzy logic based and the other
is adapting the feed rate according to the position and time at which short-circuits were
detected. The developed machine is capable of drilling micro holes in hard-to-machine materials but
also machine micro-styli and micro-needles for the metrology (micro CMM) and medical
sectors. This work also presents drilling trials performed with the machine with an orbiting
tool. Machining experiments were also carried out using electrolytes made of a combination
of HCl and NaNO aqueous solutions. The developed machine was used to fabricate micro tools out of 170μm WC-Co alloy shafts via micro electrochemical turning and drill deep holes via μECM in disks made of 18NiCr6 alloy. Results suggest that this process can be used for industrial applications for hard-to-machine
materials. The author also suggests that the developed machine can be used to manufacture
micro-probes and micro-tools for metrology and micro-manufacturing purposes.Brunel University European Commissio
Fabrication of Array Microstructures by Localized Electro-Deposition
Localized Electro-Deposition (LED) is now highly receiving scientists and researchers attention for its advantages over conventional fabrication techniques. These advantages include simplicity of the setup thus reducing the overall fabrication cost, capability of producing 2D and 3D high aspect ratio microstructures and its ability to fabricate microstructures from various raw materials. Efforts now are taking place in order to standardize the fabrication by LED to develop a commercial setup that is capable of producing complex microstructures which, in tum, can be integrated in different applications including microelectronics, microelectrochemical systems (MEMS) and sensors applications. The standardization process is performed by studying and optimizing all the parameters that control the LED process. In order to expand the current LED capabilities, this research thesis is investigating the feasibility of fabricating array of microstructures. These micro scale structures can be used as antenna arrays in ultra high frequency applications and also can be integrated in mechanical micro systems.
In this work, two LED fabrication algorithms were introduced and compared to produce arrays of micro scale features: serial deposition and parallel deposition. In serial deposition algorithm, the conventional single tip microelectrode is used to realize high aspect ratio array elements by fabricating them serially (i.e. element by element), while in the parallel deposition algorithm; the same array is fabricated by using multi-tip array microelectrode where the array microstructures are fabricated simultaneously (all array elements grow in parallel fashion). The effects of microelectrode tip material, tip geometry and the used electrolyte (raw material) on the LED fabrication process are also presented.
The new fabrication technology tested in this work enables the advancement of antennas for the upper GHz range. By implementing the parallel deposition technique outlined in this thesis, the resolution and repeatability will be enhanced and the required fabrication time of a micro system will be shorter thus enhancing the overall production rate
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Lithium‐Metal Batteries: Enabling Rapid Charging Lithium Metal Batteries via Surface Acoustic Wave‐Driven Electrolyte Flow (Adv. Mater. 14/2020)
Frontiers in Ultra-Precision Machining
Ultra-precision machining is a multi-disciplinary research area that is an important branch of manufacturing technology. It targets achieving ultra-precision form or surface roughness accuracy, forming the backbone and support of today’s innovative technology industries in aerospace, semiconductors, optics, telecommunications, energy, etc. The increasing demand for components with ultra-precision accuracy has stimulated the development of ultra-precision machining technology in recent decades. Accordingly, this Special Issue includes reviews and regular research papers on the frontiers of ultra-precision machining and will serve as a platform for the communication of the latest development and innovations of ultra-precision machining technologies
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