| Author: | Zhuang, Zhuoxuan |
| Title: | Multi-axes spatial vibration-assisted diamond cutting system for generation of hierarchical micro/nano-structured surfaces |
| Advisors: | To, Sandy (ISE) |
| Degree: | Ph.D. |
| Year: | 2023 |
| Subject: | Cutting -- Vibration Machine-tools -- Vibration Machining Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Industrial and Systems Engineering |
| Pages: | xxii, 177 pages : color illustrations |
| Language: | English |
| Abstract: | Hierarchical micro/nano-structured surfaces have been extensively applied in numerous fields, such as optics, electronics, and medical sciences, owing to their superior functional performances in the component service life. However, their fabrication presents difficulties. Electromechanical System (MEMS)-based methods and fast tool servo are currently two prevalent fabrication techniques for micro/nano-structured surfaces. Though MEM-based methods can achieve high machining efficiency, they have difficulties in fabricating hierarchical micro/nano-structured surfaces with complex three-dimensional geometry and are also only applicable to limited types of materials. Fast tool servo technology is widely employed to generate micro/nano-structures with high form accuracy and surface finish. Unfortunately, insufficient bandwidth and resolution have hindered the further application of fast tool servo in the production of hierarchical micro/nano-structured surfaces with highly complex geometry and large size. Considerable efforts have been made to enhance the machining performance of fast tool servo-based mechanical cutting. However, it is still challenging to simultaneously generate multi-scale cutting motions with high accuracy on a hierarchical scale, and research on the multi-axes vibration-assisted diamond cutting system to generate hierarchical micro/nano-structured surfaces is still lacking. In this thesis, a novel multi-axes vibration-assisted cutting device with micro-scale positioning accuracy in millimetres and nanoscale positioning accuracy in micrometres is developed to fabricate a hierarchical micro/nano-structured surface. A customized designed linear voice coil motor and a piezoelectric actuated flexure-hinge mechanism are installed into the cutting device to generate micro and nano-cutting motions, respectively. Both orders of the motion stroke have their respective position feedbacks to execute desired motions in real-time with multi-scale resolution and accuracy. Specifically, the thesis is divided into three parts. In the first part, the design and implementation of a hybrid high-performance actuation cutting device for ultra-precision machining of micro/nano-structures are proposed. Computer-aided design and magnetic simulation are used for the prototyping, and a linear voice coil motor with a 30-millimetre stroke and a high-resolution linear optical encoder is developed. A flexure-hinge with an embedded piezoelectrical actuator-compliant mechanism is installed in the cutting device, with a nanopositioning precision capacitive sensor applied to the compliant mechanism. The structure of the cutting device is designed with a small form factor in dimension in comparison to other auxiliary cutting devices for ultra-precision machine tools. The performance tests of the voice coil motor actuated slider system are systematically conducted to determine the current step response, sine mode stroke tracking, and constant force curve. The performance of the flexure-hinge mechanism is validated by static open-loop excitation. In the second part, modelling and analysis of the developed hybrid actuation cutting device, as well as micro/nano-structure machining experiments, are presented. The magnetic field simulation is also used to optimize the output force of the voice coil motor, with simulation results validated by experiments using a force sensor. In the meantime, finite element analysis is being used to investigate the flexure-hinge operation mechanism. The experimental validation of the performance testing shows that the device can perform ±0.5 mm stroke at 10 Hz for the first-order vibration and ±8 µm at 3300 Hz for the second-order vibration mechanism actuated by the piezoelectrical actuator. Furthermore, a series of micro/nano-structure fabrication experiments are conducted to demonstrate that the developed device is capable of producing micro/nano-structures. In the third part, the positioning communication device is developed to facilitate collaboration between the master CNC system and the developed multi-axes cutting system. The positioning communication device can decode two standard analogue sinusoidal position-encoded signals. This positioning synchronization device serves as a link between the master machine tool system and the developed multi-axes spatial vibration-assisted diamond cutting system. The preliminary experimental validation of the linear sinusoidal hierarchical micro/nano-structured surface is presented, and the hierarchical micro/nano-structured surface is also produced on the pre-machining bidirectional sinusoidal surface. At the end, this study presents a discussion and comparison of the hydrophobic properties of the hierarchical micro/nano-structured surfaces, with a focus on variations in size and surface profile. The findings suggest that appropriate cutting parameters can lead to an increase in the contact angle of the hierarchical micro/nano-structured surfaces. The originality and significance of the present research lie in the following aspects: (i) it contributes to a novel design of the hybrid actuation high-performance cutting device, which will generate fresh insight into the novel multi/hybrid-axes high-accuracy cutting device for the generation of the hierarchical micro/nano-structured surface; (ii) it provides the investigations to explore multi-scale high-frequency cutting performance by generating microstructured surfaces in ultra-precision machining with high accuracy and flexibility; (iii) it will be beneficial for manufacturing products with hierarchical micro/nano-structured functional surfaces and advancing their applications in a variety of fields. |
| Rights: | All rights reserved |
| Access: | open access |
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