【作者】 王玉国；

【导师】 周来水；

【作者基本信息】 南京航空航天大学 ， 航空宇航制造工程， 2007， 博士

【摘要】 近年来,随着生活水平的提高,人们对满足审美要求的雕刻类产品的需求出现前所未有的增长。传统手工雕刻生产效率低,不能满足日益增长的市场需求,数控雕刻加工就是在这一背景下诞生的。雕刻加工特色鲜明、专业性强,如果直接采用传统数控技术进行加工,通常难以胜任。为此,本文从工程实际出发,深入研究适合于雕刻行业的数控加工技术,主要内容与创新点概括如下。针对包含大量小圆弧和小线段的轮廓环,以改进扫描线求交算法为基础,提出一种复杂区域快速自动识别算法。对于输入的不合法环,算法能够报告全部出错点的精确位置,从而方便用户修正几何图形中存在的缺陷;对于输入的合法环,算法能够根据环之间的拓扑关系,在近似线性时间内快速自动识别出全部区域,区域之间可以多层嵌套。针对区域铣削加工问题,提出一种环切刀轨生成算法和一种光滑螺旋刀轨生成算法。本文环切刀轨生成算法具有运行效率高、零抬刀过渡、无残留加工区域的优点,并且适用于任意复杂区域的铣削加工。光滑螺旋刀轨生成算法以B样条理论为基础进行刀轨规划,所生成刀轨可任意阶连续,满足小刀具高速数控雕刻对刀轨光顺性的要求。在三维雕刻加工中采用先进行层切粗加工然后进行清根精加工的解决方案。提出了利用层切平面与凹雕型腔的交线和区域等距线间的等价关系计算层切刀轨,利用凹雕型腔棱线和区域中轴之间的等价关系,把清根加工刀轨计算问题转化为中轴遍历问题,降低了算法的复杂度,大幅度提高了刀轨计算效率。针对采用一般等距方法进行轮廓嵌套加工时,所加工出的凸台和凹槽在嵌套装配时易发生干涉的问题,提出一种基于凸凹轮廓协调等距的嵌套加工刀轨生成算法,该算法只需要三次等距运算即可计算出凸台和凹槽加工刀轨,确保加工出的凸台和凹槽在嵌套装配时肯定无干涉,且嵌套间隙均匀。针对立体浮雕建模与数控加工问题,提出一种几何浮雕和位图浮雕混合建模方法,通过浮雕曲面定义、浮雕曲面融合、艺术灰度图建模、图像轮廓提取等实现具有复杂细节的艺术类浮雕建模。基于反刀具等距投影法实现浮雕的无干涉精加工刀轨生成,特别适用于小刀具精雕细刻加工,并易于推广到任意类型的雕刻刀。论文研究提出的方法和算法已在自主开发的数控雕刻CAD/CAM系统中实现,并在生产中通过大量实例进行了验证。更多还原

【Abstract】 In recent years, along with the raising of living standards, the demands for aesthetic engraving products have been continuously increasing. But the traditional manual engraving method is inefficient and far from meeting the huge market reqiurements. For this reason, numerical control ( NC ) engraving machining method has been adopted to improve the productivity of engraving industry. However, because of the special characteristics of engraving products, directly applying existing NC machining strategies to NC machining of engraving products is not feasible. This dissertation makes further researches on the key technologies of NC engraving machining to pursue comprehensive solution to digitized manufacture of engraving products. The main contents and achievements are as follows:Based on improved sweep-line intersection method, an algorithm is put forward on automated recognition of complex regions from planar profiles composed of arc and straight segments. For invalid input, the exact positions where intersections occur can be detected so that it is convenient for the user to eliminate any defect in profiles. For valid input, by quickly built spatial relationship between profiles, the regions can be recognized with approximately linear time consumption. The algorithm is also suitable for the recognition of multi-nest regions.An contour-parallel tool path planning algorithm and a smooth spiral tool path generation algorithm are put forward for area milling. The former can efficiently create uncut-free tool path without tool retractions, which is applicable to milling of arbitrary shaped machining area with multiple holes. The latter can generate Cn continuous tool path with no sharp turning corners via B-spline curve fitting, which is suitable for high speed engraving with small cutting tools.A tool path scheduling methodology for 3D engrave models is presented, which performs rough machining by z-level milling first, then finish machining corner uncut material with pencil tracing. Calculation of rough machining tool path is greatly simplified using equivalence relation between curves offset from engraved pocket boundary and the intersection curve of horizontal plane and engraved pocket. Generation of pencil cleanup tool path is simplified to medial axis travel problem using equivalence relation between edges of engraved pocket and medial axis of machining region. A simple medial axis traveling strategy is also presented.A new tool path generation algorithm is presented to eliminate interferences when nesting convex mold and concave die which are machined with tool paths calculated by offsetting the 2D profile directly. With this algorithm, after only three times of profile offsetting, both tool paths for machining convex mold and concave die can be calculated simultaneously. When convex mold and concave die which have been manufactured by this algorithm are assembled together, there are absolutely no interference, and the fit clearance is of uniform distribution.By means of introducing new conception including relief surface definition, relief surface blending, art-gray-photo modeling, image edge detection et al, an approach for 3D relief modeling is presented. Based on geometry-relief and photo-relief mixture modeling, the approach can be applied to generate artistic relief with complex surfaces. Using inverse tool offset and projection method, the generation of interference-free tool path for relief finish machining is achieved, which is particularly suitable for relief machining with small tools and is extendable to arbitrary shaped engraving tools.Based on the methods and algorithms proposed above, an NC engraving software has been developed. Practical examples show the validity and effectiveness of the system.更多还原