| Optical films which have various forms of micro structures are used in LCD, LED lighting, optical instruments and other fields of application. The market need is huge. The roller is a key and core part of molding microstructure optical film manufacturing. The roller machined high quality of optical micro-structures such as micro-sphere arrays, the Fresnel structure array, prism array, pyramids array etc., has become a key constrains the optical film’s manufacturing. Micro-structures on cylindrical roller surface are complex. The shape accuracy and the surface roughness requirements are also very high. It makes the machining and manufacturing hard. The forming of ultra-precision turning is an efficient processing method. However, the reach-ability of turning process, the processing consistency of massive microstructure and the restriction of dynamic characteristics of servo tool is the key issue in need of attention in the ultra-precision machining rollers. It is different from the flat surface that cylindrical surface machining tool path is helix line for an equal diameter. The cylindrical surface is close curve, the micro-structure array generating method from cylindrical surface to flat surface, and the array’s join along circle direction become technological difficulty.As the study object for this paper, the processing of the micro-structure array on cylindrical surface is discussed at the theoretical level for the expression of micro-structure array with an unified form, explored the reach-ability of turning process of microstructure arrays from tool geometry, restriction of dynamic characteristics of servo tool etc., established the turning experimental system of the cylindrical micro-structure array, and processed experiments of typical cylindrical micro-structures. The main contents are as follows:1. A method of characterizing micro-structure array uniformly is proposed. Topological classical expressing model is used to describe the topological relationship between microstructure array elements. Combine internal-boundary-external direction model to form a unified expression of the relationship of any format of the micro-structure. For simple micro-structure array with equations described can be simplified to use a combination of the vector space of topological relations for expression. It is helpful for designing process’ s standardization and to make process procedure simply.2. Discusses the cylindrical surface microstructure workability constraints rule. First, from the geometric interference angle never occurred, specifically to study the constrain relationship between the diamond cutter geometry and the size of the micro-structural features,and the design regulation is given; Secondly, from the frequency response of the servo tool angle to study the constraints relationship between dynamic performance and microstructure arrays, the study indicates that the input frequency component except the fundamental frequency has influence to the FTS; Finally, considering the tool geometry, servo performance, machine performance, etc., forming a constraint curve for micro-structural workability coupled single factor or factors, so as to provide guidance to the selected process parameters.3. The generation algorithm of the microstructure cutting depth data is studied. The tool radius compensation algorithm suited for cylindrical microstructure is deduced; studied bilinear interpolation algorithm applied to the micro-structure without equations describing and the least square fit for curve is applied. The bilinear interpolation is found used for the discrete data and the sphere micro-structure is tested. The result indicates that this method is simple and has little error. The generation algorithm’s procedure of the microstructure cutting depth data is solved with the tool radius compensation algorithm and the bilinear interpolation.4. The influence of microstructure array processing accuracy error sources is analyzed and the evaluation index of accuracy is studied. This paper separately analyzes the impact of cylindrical diameter measuring error, tool height error and over cutting for single micro-structure outline accuracy, and the impact of controller calculating frequency for the surface quality. The impact law is found. According to the situation to the cylindrical surface, the method of measuring, the method of sample and evaluation index of accuracy is researched.5. Processing experiments of typical microstructure arrays are carried out. The processing of experiments Spherical, sinusoidal grids, aspheric, spherical irregularly distributed are carried out. Use a 3D microscope of super depth of field to observe the surface, and obtained the surface profile measurement data by the contour graph and give the quality evaluation results. The micro-structure array’s surface roughness can be nm and surface shape error can be submicron. |
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