基于Z-map模型的加工区域边界抽取算法研究

为了快速精确地进行加工区域边界抽取,给出了一种Z-map加工模型的加工区域边界抽取算法,该算法首先把Z-map模型下规则网格点阵转化为二元图进行边界抽取;然后以基于段长的方式,逐行扫描步长段,并利用上下行段之间的关系确定段左右节点的连接,以形成有向环,从而确定边界为外轮廓或为内轮廓,该算法时间复杂度为O(n),n为步长段的数量;接着通过对环中段间的连接关系分析,恢复了加工区域完整的边界信息;最后给出了该算法时间与段、行、列数之间的关系,同时与以前的算法进行了比较。结果表明,该算在效率和实施难度上都较以前算法有了一定的提高。     

基于微机的三轴数控铣削仿真系统的研究

在该微机三轴数控铣削仿真系统中，工件以一种扩充Z－map数据结构表示，并用等轴投影显示在屏幕上。加工工件的数控文件生成之后，通过系统翻译，对余料切除过程进行仿真，并实时地显示在屏幕上，从中可以容易地检查出编程错误，同时当工件和铣刀之间发生干涉时，给操作者发出警告信息。文章讨论了主要子模块的功能和改进。     

变厚度航空锻件超声C扫描技术研究

在对变厚度航空锻件用反射法进行超声波C扫描过程中,介于界面波和底波之间的缺陷识别区间随工件在各扫描点的厚度变化而变化,使得在厚度未知的情况下难以确定缺陷识别区间的范围,这给缺陷自动识别造成困难.针对此问题,通过获取工件厚度值的方法来引导检测程序确定缺陷识别区间.首先对工件表面进行超声波非接触测量,然后基于测量数据用Z-map方法计算工件在各扫描点的粗略厚度值,最后借助工件的厚度信息引导检测程序自动进行底波跟踪和确定缺陷识别区间.应用表明,该方法能较好地满足变厚度航空锻件超声C扫描的要求.     

镶齿圆刃铣刀立铣削的Z-map三维仿真研究

分析基于Z-map的圆刃铣刀三维仿真方法.推导出了用于高精度数值计算的数学算式;为保证迭代计算具有平方收敛速度,采用Newton迭代法,通过边界交点直接计算出Z-map扫描区域的网格点.这起到了减少仿真时间耗费和提高程序运行效率的作用.三维仿真实例说明,该算法对于提高仿真精度和表面加工误差分析具有实际意义.     

基于Z-map模型的自由曲面无干涉刀具轨迹生成算法研究

刀具轨迹生成是自由曲面零件数控加工中重要的研究内容.本文分析了自由曲面数控加工中常用的刀具轨迹生成策略和方法,设计和实现了一种基于Z-map结构的自由曲面无干涉刀具轨迹生成算法.本算法采用进化算法进行刀具干涉检测,不仅解决了生成刀具轨迹时因走刀步长不合理而产生的过切问题,而且也确保了生成的刀具轨迹为无干涉刀具轨迹.     

基于动态四叉树的数控铣削加工仿真的研究

提出采用基于自相似动态四叉树（Quadtrees）的思想进行实体造型,实现数控仿真加工毛坯实体的动态建模,从而在一定程度上解决数控加工仿真过程中毛坯除料算法的运算速度缓慢而造成的真实感差的问题,并通过一个零件加工仿真验证了该算法的可行性和有效性。     

Development of a virtual machining system, part 3: cutting process simulation in transient cuts

In Parts 1 and 2 of this three-part paper, a mechanistic cutting force model was developed and machined surface errors for steady cuts under fixed cutting conditions were predicted. The virtual machining system aims to simulate and analyze the machining and the machined states in a general flat end-milling process. This frequently involves transient as well as steady cuts. Therefore, a method for simulating the cutting process of transient cuts needs to be developed to realize the virtual machining system concept. For this purpose, this paper presents a moving edge-node (ME) Z-map model for the cutting configuration calculation. The simulation results of four representative transient cuts in two-dimensional pocket milling and an application of off-line feed-rate scheduling are also given.

In transient cuts, the cutting configurations that are used to predict the cutting force vary during the machining operation. The cutting force model (Part 1) and surface error prediction method (Part 2) were developed for steady cuts; these are extended to transient situations using the ME Z-map model to calculate the varying cutting configurations efficiently. The cutting force and surface errors are then predicted. To validate the feasibility of the proposed scheme, the measured and predicted cutting forces for transient test cuts were compared. The predicted surface error maps for transient cuts were constructed using a computer simulation. Also, off-line feed-rate scheduling is shown to be more accurately performed by applying the instantaneous cutting coefficients that were defined in Part I.     

基于Z-map理论的喷枪轨迹生成方法

喷漆机器人作为一种先进的涂装生产设备已广泛应用于产品内外表面的喷涂,由于现代工业产品外形相当复杂,如何实现涂层均匀化变得极为重要。基于Z-map理论,在自由曲面CAD模型的基础上,将自由曲面三角网格化得到多面体模型,然后利用Z-map方法实现了等距喷涂情况下喷涂节点的坐标及其法向量的提取,将喷涂节点插补优化后连接为喷枪的喷涂轨迹,从而实现了自动生成自由曲面上喷枪轨迹。最后,以一汽车CAD模型为例生成了机器人喷涂轨迹。     

Design of parallel dual-energy X-ray beam and its performance for security radiography

A new concept of dual-energy X-ray beam generation and acquisition of dual-energy security radiography is proposed. Erbium (Er) and rhodium (Rh) with a copper filter were positioned in front of X-ray tube to generate low- and high-energy X-ray spectra. Low- and high-energy X-rays were guided to separately enter into two parallel detectors. Monte Carlo code of MCNPX was used to derive an optimum thickness of each filter for improved dual X-ray image quality. It was desired to provide separation ability between organic and inorganic matters for the condition of 140 kVp/0.8 mA as used in the security application. Acquired dual-energy X-ray beams were evaluated by the dual-energy Z-map yielding enhanced performance compared with a commercial dual-energy detector. A collimator for the parallel dual-energy X-ray beam was designed to minimize X-ray beam interference between low- and high-energy parallel beams for 500 mm source-to-detector distance.     

A Z-map update method for linearly moving tools

In numerically controlled (NC) machining simulation, a Z-map has been frequently used for representing the workpiece. Since the Z-map is usually represented by a set of z-axis aligned vectors, the machining process can be simulated through calculating the intersection points between the vectors and the surface swept by a machining tool. In this paper, we present an efficient method to calculate those intersection points when automatically programmed tool-type tools move along a linear tool path. Each of the intersection points can be expressed as the solution of a system of non-linear equations. We transform this system of equations into a single-variable equation, and calculate the candidate interval in which the unique solution exists. We prove the existence of a solution and its uniqueness in this candidate interval. Based on these properties, we can effectively apply numerical methods to finally calculate the solution of the non-linear equations within a given precision. The whole process of NC simulation is achieved by updating the Z-map properly. Our method can improve accuracy greatly while increasing processing time negligibly in comparison with previous Z-map update methods, making it possible to verify the tool path more accurately and reliably.