Papers by Keyword: Freeform Surfaces

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Authors: Ling Bao Kong, Chi Fai Cheung, Wing Bun Lee, Sandy To
Abstract: This paper presents an integrated platform for modelling and measurement of freeform surface generation in ultra-precision raster milling. It is composed of several components which are optics design component, tool path generator, modelling system, measurement system, evaluation component, compensation component and optimization component, respectively. The research emphasizes on modelling and simulation of freeform surface generation, the prediction of the cutting performance and hence the optimization of cutting strategy in the ultra-precision raster milling of freeform surfaces. A measurement system is also proposed to carry out a fast and efficient measurement plan of freeform surfaces. Non-uniform Rational B-Spline (NURBS) will be employed for the development of the integrated platform which will meet Standard for the Exchange of Product model data (STEP).
Authors: Li Li Han, Qing Wei Zhang, Kai Jia
Abstract: In order to solve the problem of high intensity and low efficiency by manual labor during the polishing machining of mold free-form surface, this paper present a method for path generation of robot automatic polishing based on bounding box. Firstly, ascertain the location and direction of the mold by constructing a box that is most close to the mold. Secondly, generate the tool path by introducing the improved direction-parallel machining. Finally, by using Visual C++6.0 development tool, the algorithm discussed above has been implemented and a software for trajectory generation has been developed. The results show that the method can generate the tool path better along the surface contour and is simple, effective. Besides, the software supplies a visible trajectory for robot polishing so that the unreasonable points can be modified before machining.
Authors: Yu Cao, Ting Ting Yu, Xue Lin Hu, Feng Pin Li
Abstract: A new method of parallel projection galvanometer scanning (PPGS) is presented, as a low-cost, flexible, trans-scale solution for laser material processing on freeform surfaces. The parallel projection transformation is used for mapping three-dimensional space curves to terraced two-dimensional plane graphics that each one is suitable for traditional galvanometer scanning method. For implementation of the PPGS method, a parallel projective laser scanning system with the combination of galvanometer and telecentric lens is needed, that the laser is directed along the space curve path on freeform surface part without deviation when the x-y axis galvanometer is scanning the mapping graphic path of the parallel projection plane. In practice, the existing 3D galvanometer scan system, "3+2" and rob-scan system are alternative choices in different application situations.
Authors: Wee Keong Neo, Mark Derek Nadhan, A. Senthil Kumar, Mustafizur Rahman
Abstract: Fast/slow tool servo (FTS/STS) technology plays an important role in machining freeform surfaces for the modern optics industry. The accuracies of these surfaces not only depend on the performance of the FTS/STS but also on the methods of tool path generation (TPG). Current methods of pre-compensating tool nose radius and control dynamics still do not address the inherent profile errors arise from the methods of TPG. Furthermore, it is also not efficient to characterize a freeform surface in the post-machining stage, giving a high risk of failing to meet the accuracy requirements. In this paper, a profile error analysis (PEA) is introduced into the pre-machining stage to address this inherent profile error. PEA is carried out to compare two methods of TPG, namely the constant angle and constant arc methods and optimizes the number of cutting points in the TPG. Thus, the profile accuracy can be pre-determined to meet accuracy requirements by determining the appropriate TPG method with a least number of the cutting points. In the experiments, sinusoidal wave grid and micro-lens array surfaces are fabricated and their profiles successfully achieve the accuracy tolerance of 1 μm. These further credit the capability of PEA as an effective and accurate tool in improving profile accuracies and meeting accuracy requirements.
Authors: Shuang Man Xu, Wei Jing Li
Abstract: In order to solve the freeform surface spray planning problem in spray industrial, this article proposed a model of the spray gun and description of the spray procedure. Then, the article presents a rapid planning method based on CAD model of the workpiece. With this method, the spray trajectory is constructed by the path points normal vector and S-shaped path using CAD model. In ABB's RobotStudio simulation software, a spray experiment is carried out. The simulation results show that this method can effectively simplify the offline planning process and save processing time.
Authors: Ri Liang Liu, Yi Ran Wang, Cheng Rui Zhang, Yuan Fan Xu
Abstract: In order to realize STEP compliant NC manufacturing, STEP-NC (ISO 14649) has been developed over last decade by the International Standard Organization as a new data model for CNC programming. This paper proposes a framework for STEP compliant NC programming of the freeform surfaces. The system is supposed to read the CAD model produced by commercial CAD/CAM software and represented in STEP format, prepare the process information, and finally generate the STEP-NC compliant program. Major issues relating to CAD data extraction, toolpath calculation and NC program generation are presented.
Authors: Ming Jun Ren, Chi Fai Cheung, Ling Bao Kong
Abstract: The fabrication of ultra-precision freeform surfaces possessing non-rotationally symmetric geometry and sub-micrometre form accuracy requires an efficient positioning method for precisely locating the position of the workpiece on the machine with high repeatability during the manufacturing cycle. This paper presents an initial attempt to develop a fiducial aided positioning (FAP) method for precisely locating the freeform workpiece on multi-axis machine tools in order to improve the accuracy and efficiency in the manufacturing of ultra-precision freeform surfaces. The FAP method makes use of fiducials to establish intrinsic surface features of the freeform workpiece which are used to determine the coordinate transformation between the coordinate frame of the workpiece and the machine in the machining process and the measurement process. A preliminary simulation experiment was conducted to verify the technical feasibility of the proposed FAP method. The results show that the FAP method is technically feasible to establish a link between the machining and measurement process so as to improve machining accuracy.
Authors: H.F. Li, Chi Fai Cheung, Ling Bao Kong, Wing Bun Lee, Sandy To
Abstract: Ultra-precision freeform surfaces have become widely used in advanced optics manufacture. Although these surfaces can be fabricated by ultra-precision freeform machining technology with sub-micrometer form accuracy and surface finish in nanometer range, our current understanding on the evaluation of surface quality of these surfaces is still far from perfect. In this paper, a study of measurement technology for ultra-precision freeform surfaces is presented.
Authors: Su Juan Wang, Suet To, Chi Fai Cheung, Wing Bun Lee
Abstract: Ultra-precision raster milling (UPRM) can directly achieve the fabrication of threedimensional non-axisymmetric freeform components with nanometeric surface finish and submicrometric form accuracy. During the past few years, a lot of research on computerized numerical control (CNC) machining technologies has been conducted; however, little of this research makes any contribution to UPRM. This paper studies the mechanism of scallop height generation for UPRM. Through analyzing the cutting edge locus and the scallop height generation mechanism, a model for feed-intervals and for raster-interval scallop height generation, are presented. Parameters such as selection of feed direction (vertical cutting and horizontal cutting), feed rate, spindle speed, tool nose radius, swing distance, feed length and raster distance have been taken into consideration in the scallop generation models.
Authors: Shu Kun Cao, Li Song, Zhi Ming Sui, Chang Zhong Wu, Jia Jia
Abstract: In view of the randomness of determining free-form surface machining processing program and the complexity and the unpredictable nature of process, in this paper we proposed automatically determination of free-form surface CNC processing technical parameters, research on processing equipment selection algorithm and system development. The method, firstly determine process parameters on the base of the free-form surface characteristics and the precision requirements, or by calculation methods, or by querying the process repository, and secondly, query the existing equipment and their working status from resources repository on the base of the process parameters to select processing equipment, and then have the free-form surface machining, finally, track the parts processing and the process working conditions of equipment.
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