【作者】 朱林森；

【导师】 宾鸿赞； 汤漾平；

【作者基本信息】 华中科技大学 ， 机械制造及其自动化， 2007， 博士

【摘要】 船模是根据船体的型线图和型值表,按一定比例缩小制造的船体模型,是预测实船航行性能和辅助船舶科研教学的重要工具。本文针对船模曲面尺寸大、形状复杂、木材材质的特点,特别是形状对称的特性,基于一种新型的数控对称加工方法,深入系统地研究了船模曲面分片造形、分片加工的理论方法。根据船模曲面的型线图和型值表,本文研究了两种构造船模曲面三维型线网格结构的方法:型线重构法和几何变换法。船模曲面的三维型线网格结构是船模曲面分片造形的直接依据。本文重点研究了插值型线的两种曲面造形方法:蒙皮法和过曲线网格法。通过分析比较两种方法构造船模曲面的造形效果,指出过曲线网格法是适合船模曲面三维造形的主要方法;鉴于过曲线网格法构造曲面的前提是要求存在拓扑矩形网格结构,而船模曲面的三维型线网格结构一般不满足这个要求,为此本文提出了一种局部包容和分片造形方案;船模曲面经包容分片后,满足了过曲线网格法的要求,最大限度地利用了船模曲面的三族型线,保证了船模曲面的造形精度和光顺效果。以高效、高精加工为目标,以四坐标对称加工机床为加工平台,本文归纳了船模曲面对称加工刀具路径规划的四个准则:木材切削准则、对称加工准则、分片加工准则和水线加工准则;根据木材切削的经验公式绘制了船模曲面粗加工的工艺参数曲线;基于上述刀具路径规划准则,提出了一种分阶段、分区域的分片加工工艺方案,并通过数控编程对该方案进行了仿真验证。针对大型对称曲面的数控加工,本文定义了一种新的数控对称加工方法,分析了数控对称加工的关键技术,研究了对称加工的实现机理和防撞技术。基于以上研究成果,自主研制开发了国内首套四坐标船模曲面数控对称加工系统。实际加工结果表明:该系统将船模曲面的加工时间由手工加工的45个工作日缩短为7个小时,将船模曲面的对称误差由1.5mm减小到0.47mm,相对于传统的四坐标单刀加工机床,加工效率提高了85%。更多还原

【Abstract】 A ship model, which is usually made of wood according to the ship offsets table and lines plan in contractible scale, is an important tool to forecast navigational capability of a real ship and to assist scientific research & teaching work. In allusion to big size, complex shape, wooden material, especial symmetrical characteristic of ship model surface (SMS), this thesis studied systemically on the methods of SMS divisional modeling & divisional machining based on symmetrical machining technology.Based on SMS offsets table and lines plan, the thesis investigated two modeling methods for the 3-D lines mesh: Lines Reconstruction and Coordinate Transform. The 3-D lines mesh is the direct modeling foundation of SMS.The thesis investigated two surface modeling methods by lines interpolation: Skinning and Through Curve Mesh (TCM). Comparing the modeling effects of SMS sheets by the two methods, the thesis pointed out that TCM is suitable to the SMS modeling. Because the modeling precondition of TCM is a curve mesh, however, The SMS 3-D lines mesh generally can not satisfy the condition, local region enveloping and surface division project is put forward. Through local region enveloping project and surface division project, the ship model surface can satisfy with the demand of TCM, thus, the modeling of the ship model surface can make use of lines farthest, which ensure the modeling precision and fairness of the whole SMS.Aiming at the requirements of high efficiency and high precision machining, 4-axis NC symmetrical machine being as the machining platform, four tool path planning rules on SMS NC symmetrical machining have been concluded: wood cutting rule, symmetrical machining rule, divisional machining rule and water line machining rule. The processing parameter curves of SMS roughing machining wre drawn on the base of wood cutting formula. Based on the above four rules, a machining scheme by phase division and region division has been put forward, and it is simulated after its NC programming.In allusion to the NC machining for a large symmetrical freeform surface, the thesis defined a new-style symmetrical machining method, analyzed its key technologies, investigated the realizing mechanism of symmetrical machining and the technology for avoiding collision. Based on the above research work, the first 4-axis NC symmetrical machining system for SMS in China has been successfully developed. The actual machining results confirm that the system can shorten the machining time of a twin-skeg SMS from 45 working days needed for the current handcrafting method to 7 hours, and reduce the symmetric error from 1.5mm to 0.47mm; the machining efficiency of the 4-axis symmetrical machine is enhanced 85% higher than that of a traditional 4-axis single-cutter machine.更多还原