| Author: | Yuan, Wei |
| Title: | Theoretical and experimental investigation of the tool indentation effect on ultra-precision tool servo diamond cutting of three-dimensional microstructured surfaces |
| Advisors: | Cheung, C. F. (ISE) Lee, W. B. (ISE) Chan, Joe (ISE) Li, L. H. (ISE) |
| Degree: | Ph.D. |
| Year: | 2022 |
| Subject: | Cutting tools Microstructure Surfaces (Technology) Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Industrial and Systems Engineering |
| Pages: | xviii, 154 pages : color illustrations |
| Language: | English |
| Abstract: | The growing demand for producing three-dimensional (3D) microstructured surfaces, such as microlens array has driven the development of ultra-precision diamond cutting technologies. Ultra-precision tool servo diamond cutting (UTSDC) has been used to fabricate many kinds of 3D microstructures. Unlike traditional turning or grooving, the depth of cut varies in UTSDC. As the diamond tool alternatively moves upward and downward in the thrust cutting direction, extra amount of the work material under the tool edge is deformed elastically and plastically, which produces the indentation force and affects the generated surface topography. The effect is named indentation effect in the present study. However, most previous studies focus on the cutting mechanism and ploughing mechanism in orthogonal cutting condition where the depth of cut is invariant. The effect of indentation mechanism in UTSDC has been overlooked. In this regard, this study aims to addressing the problems related to the tool indentation effect arising in the UTSDC of microstructured surfaces. The indentation effect on the material removal mechanism and surface generation is firstly investigated in UTSDC of special inverted pyramid microstructures under different cutting conditions. It is found that the inclined angle between the tool path direction and the main cutting direction plays a key role in the determination of the material spring back. A material spring back model in UTSDC is built taking the inclined angle and the uncut chip thickness into consideration. The burr formation is also studied, and it is found that large inclined angle in the cut-out process generates side burrs on the edge of the microstructures. The analysis of cutting forces shows that the indentation force can be determined by the asymmetric force, which is the difference of thrust forces in cut-in stage and cut-out stage at the same depth of cut. The characteristics of indentation force and material spring back indicates that the indentation mechanism is dominant in the cut-in process where the inclined angle is large, while the shearing mechanism is dominant in the cut-out process. To give a deeper insight of the tool indentation mechanism, a mechanistic analytical model is built to estimate the indentation force with variation of uncut chip thickness. The proposed model makes use of the discontinuous step functions to determine the designed tool path so that the indentation theory can be utilized to estimate the force in the indentation steps. The round-nose cutting tool is also discretized, which allows the determination of the pressure distribution based on an analytical model for an inclined punch with a rounded edge radius. The simulation results show that the proposed model can predict well the main trend of the indentation force under various cutting conditions. The effect of variation of depth of cut and cutting speed on the variation of surface topography is also investigated. A fast and comprehensive dynamic model is developed for predicting the surface generation in UTSDC of microlens array. The proposed model can predict the root-mean-square RMS values of the surface primary profile and the dynamic force acting on the force sensor based on the tool path, the indentation mechanism, and the dynamics of cutting system. The present study contributes significantly to the reveal and a better scientific understanding of indentation effect and its effects on the cutting mechanics, the cutting forces, the dynamics of the cutting system, and hence the surface generation in UTSDC of 3D microstructures under variation of depth of cut conditions. The theoretical and characterization models developed in the present study will allow the prediction and characterization the indentation effect on variation of cutting force and the variation of surface topography in UTSDC of 3D microstructures. This study will provide a way forward for the optimization of surface quality in UTSDC of 3D microstructured surfaces. |
| Rights: | All rights reserved |
| Access: | open access |
Copyright Undertaking
As a bona fide Library user, I declare that:
- I will abide by the rules and legal ordinances governing copyright regarding the use of the Database.
- I will use the Database for the purpose of my research or private study only and not for circulation or further reproduction or any other purpose.
- I agree to indemnify and hold the University harmless from and against any loss, damage, cost, liability or expenses arising from copyright infringement or unauthorized usage.
By downloading any item(s) listed above, you acknowledge that you have read and understood the copyright undertaking as stated above, and agree to be bound by all of its terms.
Please use this identifier to cite or link to this item:
https://theses.lib.polyu.edu.hk/handle/200/11802