|Author:||Mak, Chung Hong|
|Title:||An investigation of modelling and measurement of surface generation in single-point diamond turning of microstructure pattern rollers|
|Advisors:||Cheung, Benny (ISE)|
Machine-tools -- Monitoring.
Hong Kong Polytechnic University -- Dissertations
|Department:||Department of Industrial and Systems Engineering|
|Pages:||xxi, 151 pages : illustrations (some color)|
|Abstract:||In this project, a replica-based measurement method is proposed and experimental validation is provided. The measurement work on bulk workpieces with a micro structure surface can be made even on the machine. Moreover, an experiment concerning the factors affecting V-groove formation is conducted. The relationship between the different numbers of V-groove per zone, different depths of cut per V-groove, different pitches per V-groove and different numbers of cuts per V-groove on various materials is investigated. Last but not least a kinematic-based simulation model was built for predicting the V-groove formation on the precision roller. Plastic films and flat display panels with embossed micro-structure patterns and specific optical properties have been widely used in various applications. The traditional manufacturing technology, based on injection moulding, is inadequate as itencompasses a lot of technical challenges. Nowadays, the rolling imprint method is one of the emerging technologies for the fabrication of plastic films and flat display panels. However, the quality of the embossed micro-structure patterns on the films heavily relies on the accuracy of the precision rollers. Although there has been extensive research work on the design and precision manufacturing of precision rollers for supporting roll-to-roll technologies, relatively little research work has been reported on the study of factors affecting surface generation and measurement of the micro-structure patterns in single-point diamond turning (SPDT) of precision rollers. As the size and weight of the precision rollers are usually bulky and heavy, this makes the traditional offline measurement of the surface quality of their cylindrical surfaces difficult. Moreover, SPDT of the precision rollers is a complex process and the machine time is relatively long. It is not affordable to machine the rollers by a trial-and-error approach. This demands the development of appropriate measurement methods so as to ensure that the machined surfaces can be achieved without the need to remove the precision rollers from ultra-precision machines. Moreover, it is also indispensible to develop theoretical models and systems to support the prediction and optimization of the surface generation of the microstructure on the precision rollers. As a result, this study aims at investigating the in-process measurement method and the factors affecting surface generation in the SPDT of micro-structure pattern rollers. There is also a need to develop model-based simulation to predict the surface generation and surface quality of the machined surfaces without the need for expensive trial cutting tests. The study started with the development of a replica-based measurement method which makes use of a replica to acquire the surface topography of the measured surface, and the replica is then measured using a metrological instrument. The proposed replica-based measurement method attempts to address the limitations of the traditional offline and contact measurement of the V-grooves on the cylindrical surface of bulk precision rollers. A series of measurement experiments was conducted to evaluate the effectiveness of the method. The results show that there exists an unreachable depth at the bottom of the V-groove when using the touch probe of a contact measurement instrument such as the Form Talysurf. With the successful development of the proposed replica-based measurement method, it is technically feasible to measure and compensate for the error due to the unreachable depth of the V-groove pattern on the precision rollers. With appropriate further development work, the method has great potential to be applied in measuring microstructure surfaces on precision rollers.|
Based on the results of the development of the replica-based measurement method, a series of experiments was conducted to study the factors affecting the surface generation in SPDT of the microstructure pattern on precision rollers. The results show that there are process factors and material factors which affect the surface generation in SPDT of microstructure pattern rollers. The process factors include depth of cut, width of cut, and tool geometry, while the material effect due to material swelling and recovery is found to contribute significantly to the surface generation. The results provide an important means for the modelling and measurement of a V-groove patterned roller. To make the surface generation of V-groove pattern rollers more predictable, a model-based simulation system has been established for predicting the 3D surface topography and form error of the V-groove pattern fabricated on precision rollers. The system takes into account the kinematic and geometrical errors of the ultra-precision machine as well as the material effect in SPDT of V-groove patterns on precision rollers. It is built based on a kinematic model, a geometric error model, an empirical analysis of material effect and a surface generation model. A prototype system has been built using a Matlab software package and a series of simulation and cutting experiments were conducted to assess the performance of the system. The predicted results by the system were found to agree well with the measured results. On the whole, this study not only contributes significantly to a better understanding of the factors affecting surface generation in SPDT of micro-structure pattern rollers but also provides an important means for the prediction and measurement of surface quality of the fabricated microstructure patterns. This is vital for the technological advancement of ultra-precision machining and precision measurement technologies.
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