MasterCAM直纹加工策略

正目前数控加工程序的编制,已普遍采用计算机自动编程的方法。在自动编程中,首先须从CAD开始进行零件的造型。常用的零件造型方法一般可分为线架造型、曲面造型及实体造型;其中线架造型由点、直线和曲线等组成,用以描述几何对象的轮廓及断面特征。但在自动编程中,容易出现刀具路径的重复、空刀等情况,编程人员提高编程水平之一就是减少刀具路径的重复。1.直纹加工的策略(1)策略一:图1为我校数控实训中常见加工零件,材料是铝合金,加工刀具是高速钢刀,加工设备是数控铣床。加工图中左边的8 mm×45°斜壁,用得较多的加工方法是外形铣削铣斜壁。我校数控     

复杂零件造型与刀具路径规划同步处理方案及应用

CAD／CAM集成数控编程系统进行零件数控加工的一般过程是：分析加工零件、待加工表面→确定加工方法、编程原点、编程坐标系→对待加工零件进行几何造型→确定加工工艺、选择合适的刀具→刀具轨迹生成及编辑→刀具轨迹验证、程序后置处理→机床通信、加工。     

基于CATIAb V5典型曲面的数控加工与自动编程

以典型曲面模型为例,利用CATIA建模模块进行曲面造型设计,并根据该零件结构特点进行工艺分析,使用CATIA的CAM加工模块设置加工参数实现自动编程,由程序后处理自动生成NC代码,最后总结整个加工仿真过程中遇到的困难并提出相应的解决方法,从而达到缩短编程时间、提高工作效率和编程质量的目的,有效保证零件的加工精度。     

基于UG的复杂曲面零件的数控加工

以一个复杂曲面零件模型为例,论述了UG CAO/CAM系统在数控加工中的应用过程：利用UG的建模模块对其进行曲面造型设计,并根据该零件结构特点进行工艺分析,使用UG的CAM加工模块设置加工参数实现自动编程,由程序后处理自动生成NC代码,最后将NC代码导入数控机床加工出实体零件,从而达到缩短编程时间,提高工作效率和编程质量的目的,有效地保证了零件的加工精度。     

基于 PowerMILL 的造型车模五轴加工编程模版开发

探讨造型车模五轴加工工艺要点,研究基于先进CAM软件计算造型车模五轴加工刀具路径编程工艺,提出了对该模型的五轴加工编程工艺规范化思路以及具体实施方案,基于PowerMILL、易语言编程系统开发了造型车模五轴加工编程工艺模版库。     

基于CAXA软件的复杂曲面数控加工仿真

CAXA制造工程师是一个开放的设计和加工工具。文中以吊钩锻模为例,针对复杂曲面零件在CAXA环境下自动编程及加工的一些方法进行探讨,从造型设计、自动编程、加工工艺、建立加工模型和仿真加工技术等方面来分析CAXA制造工程师在三维造型设计与仿真加工中的优势与特点。     

基于CAXA-ME的零件加工造型方法分析及仿真校验

交互式图形自动编程的实现以CAD技术为前提,而CAD造型效率有助于缩短机械零件编程时间和提升数控设备综合利用率。为此,分析了零件加工造型和设计造型的区别,基于CAXA制造工程师CAD/CAM功能模块用实例研讨了零件加工造型方法,通过模拟仿真验证了生成轨迹的正确性,提出了创建加工造型的注意事项。     

三维体元构造切削法（CCG）造型原理研究

以车刀为例，介绍了三维刀具图形的数学模型，以刀具体元构造坐标系为基础，提出轴网，弧网，面架，设置层距等三维辅助绘图方法，进一步论述了刀具参数化实体造型中几何体元划分和构成方法，以及构造切削法数据库驱动造型模型，利用上述创造性思维模型加上智能化编程可实现刀具三维实体自动化构成，即模拟加工过程构成零件三维图形；各零件又可模拟装配工艺过程，实现自动三维图形装配，从而完成装配图的绘制。     

CAXA制造工程师环境下奔驰车标的CAD/CAM

CAXA制造工程师是一款集CAD/CAM功能于一体的软件,本文结合该软件自动编程的4个步骤,提出了奔驰车标零件的加工方案。详细介绍了基于2013R2版环境下,该零件的设计与制造过程,重点研究了奔驰车标CAD几何造型、生成刀具轨迹、后置设置、生成机床代码等。简要介绍了验证数控编制程序的方法,其为一种基于仿真软件下的虚拟机床加工。研究表明,依据CAD/CAM编程过程,可实现复杂零件的自动编程,为初学CAD/CAM软件的人员提供了参考。     

整体式叶轮的三维造型及数控加工

整体式叶轮的加工应在多轴数控加工中心上进行,并借助CAD/CAM软件和数控加工仿真软件,进行三维造型、自动编程和数控仿真加工.应用CAXA制造工程师和VERICUT软件,对整体式叶轮进行三维造型、自动编程和仿真校验,可在实际数控加工该零件之前,及时检查出多轴数控加工程序中出现的刀具干涉与碰撞等问题;对多轴数控加工程序的不足进行调整和修改,可提高多轴数控加工中NC程序的准确性和可靠性;协助工艺员编制出准确和合理的数控加工工艺,可保证整体式叶轮数控加工的高效率、高质量和高精度.     

A new accurate curvature matching and optimal tool based five-axis machining algorithm

Free-form surfaces are widely used in CAD systems to describe the part surface. Today, the most advanced machining of free from surfaces is done in five-axis machining using a flat end mill cutter. However, five-axis machining requires complex algorithms for gouging avoidance, collision detection and powerful computer-aided manufacturing (CAM) systems to support various operations. An accurate and efficient method is proposed for five-axis CNC machining of free-form surfaces. The proposed algorithm selects the best tool and plans the toolpath autonomously using curvature matching and integrated inverse kinematics of the machine tool. The new algorithm uses the real cutter contact toolpath generated by the inverse kinematics and not the linearized piecewise real cutter location toolpath.     

汽轮机弯扭叶型面的四轴数控加工方法研究

通过对汽轮机弯扭叶型面的四轴数控加工方法研究 ,提出此类型面数控加工的特点以及相应的刀轨设计、数控程序的后置处理方法     

Part accuracy improvement in two point incremental forming with a partial die using a model predictive control algorithm

As a flexible forming technology, Incremental Sheet Forming (ISF) is a promising alternative to traditional sheet forming processes in small-batch or customised production but suffers from low part accuracy in terms of its application in the industry. The ISF toolpath has direct influences on the geometric accuracy of the formed part since the part is formed by a simple tool following the toolpath. Based on the basic structure of a simple Model Predictive Control (MPC) algorithm designed for Single Point Incremental Forming (SPIF) in our previous work Lu et al. (2015) [1] that only dealt with the toolpath correction in the vertical direction, an enhanced MPC algorithm has been developed specially for Two Point Incremental Forming (TPIF) with a partial die in this work. The enhanced control algorithm is able to correct the toolpath in both the vertical and horizontal directions. In the newly-added horizontal control module, intensive profile points in the evenly distributed radial directions of the horizontal section were used to estimate the horizontal error distribution along the horizontal sectional profile during the forming process. The toolpath correction was performed through properly adjusting the toolpath in two directions based on the optimised toolpath parameters at each step. A case study for forming a non-axisymmetric shape was conducted to experimentally validate the developed toolpath correction strategy. Experiment results indicate that the two-directional toolpath correction approach contributes to part accuracy improvement in TPIF compared with the typical TPIF process that is without toolpath correction.     

面向特征的整体叶轮五轴数控加工技术

基于特征制定整体叶轮数控加工工艺,同时兼顾叶轮的工作要求和加工刚度,利用UGNX3.0提供的Interpolate方式规划流道特征的开粗加工和精加工轨迹,Swarf方式规划叶片特征的侧铣加工轨迹.经过仿真验证加工轨迹的合理性,最后使用配有HNC-22M数控系统的五轴加工中心VMC-1100成功加工了整体叶轮.     

等残留轨迹规划方法在高速加工中的应用研究

在数控加工中,加工轨迹规划方法直接影响到加工的效率及质量,尤其在高速加工中轨迹规划方法合理的选择关系到加工的成败.本文对等残留轨迹方法与等参数线轨迹规划方法的在高速加工中加工效率和加工后表面残留高度进行了分析比较,探讨了两种方法加工效率和表面质量与自由曲面曲率的关系.结果表明等残留高度法能根据自由曲面状况,不同程度的提高加工效率及表面质量,并与曲面曲率具有较大的相关性.     

Process modeling and toolpath optimization for five-axis ball-end milling based on tool motion analysis

In free-form surface machining, the prediction of five-axis ball-end milling forces is quite a challenge due to difficulties of determining the underformed chip thickness and engaged cutting edge. Part and tool deflections under high cutting forces may result in poor part quality. To solve these concerns, this paper presents process modeling and optimization method for five-axis milling based on tool motion analysis. The method selected for geometric stock modeling is the dexel approach, and the extracted cutter workpiece engagements are used as input to a force prediction. The cutter entry?Cexit angles and depth of cuts are found and used to calculate the instantaneous cutting forces. The process is optimized by varying the feed as the tool?Cworkpiece engagements vary along the toolpath, and the unified model provides a powerful tool for analyzing five-axis milling. The new feedrate profiles are shown to considerably reduce the machining time while avoiding process faults.     

自由曲面叶片数控加工刀具轨迹规划方法

研究了自由曲面叶片数控加工刀具轨迹规划方法。解决了两个问题:(1)叶片曲面建模过程中的布尔操作破坏了曲面参数域,从而在叶尖处造成冗余刀轨,并在叶根处有可能形成干涉;(2)叶片前后缘处曲率半径的剧烈变化导致步长计算容易超差从而造成啃切现象。针对问题(1),本文提出一种新的参数映射方法,将裁剪后的曲面参数域重新映射到一个规范化的参数域上去,并在新的参数域上规划刀轨;针对问题(2),本文提出一种改进的弦截法来计算走刀步长。该方法收敛速度快,且避免了对复杂函数的求导,计算量小。同时本文采用搜索解空间,并修改变量替换方式来避免该方法收敛于错误的解。仿真实例表明,本文方法达到了预期效果,在提高了加工效率的情况下,避免了啃切现象的发生。     

Tool-path planning for rough machining of a cavity by layer-shape analysis

In the manufacture of parts with sculptured cavities from prismatic stock, rough machining usually constitutes most of the machining time owing to the significant difference between the stock and the part shape. When using 2 1/2-D milling or a contour-map approach to do the rough machining, the appropriate selection of tool-path pattern for each cutting layer can significantly reduce rough machining time and hence increase productivity. In this paper, the commonly used toolpath patterns are summarised. A knowledge-based parametric approach for optimising the toolpath pattern of a given cutting layer is proposed. Then, a novel methodology is developed to calculate an arbitrary polygon area and locate the concave cavities in the polygon. Procedures for cutting-layer-shape analysis and the optimal comprehensive tool-path pattern generation are also built and proposed in this paper. These procedures can not only be applied to sculptured cavity parts with simple islands, but also to parts with arbitrarily-shaped islands. Finally, an example is given to illustrate the reasoning process.     

Pre-compensation for continuous-path running trajectory error in high-speed machining of parts with varied curvature features

Parts with varied curvature features play increasingly critical roles in engineering, and are often machined under high-speed continuous-path running mode to ensure the machining efficiency. However, the continuous-path running trajectory error is significant during high-feed-speed machining, which seriously restricts the machining precision for such parts with varied curvature features. In order to reduce the continuous-path running trajectory error without sacrificing the machining efficiency, a pre-compensation method for the trajectory error is proposed. Based on the formation mechanism of the continuous-path running trajectory error analyzed, this error is estimated in advance by approximating the desired toolpath with spline curves. Then, an iterative error pre-compensation method is presented. By machining with the regenerated toolpath after pre-compensation instead of the uncompensated toolpath, the continuous-path running trajectory error can be effectively decreased without the reduction of the feed speed. To demonstrate the feasibility of the proposed pre-compensation method, a heart curve toolpath that possesses varied curvature features is employed. Experimental results indicate that compared with the uncompensated processing trajectory, the maximum and average machining errors for the pre-compensated processing trajectory are reduced by 67.19% and 82.30%, respectively. An easy to implement solution for high efficiency and high precision machining of the parts with varied curvature features is provided.     

Tool path generation method for multi-axis machining of helical milling cutter with specific cross-section profile

The geometry of helical milling cutter with specific cross-section profile is normally generated with form cutter by the toolpath generating method. The general purpose CAD/CAM software can generate the cutter location file of this class of product only by the sculpturing method. To obtain the flexibility of machining process, this paper presents an interference-free toolpath generating method for semi-finish and finish machining of the helical milling cutter. The method for design and machining of the helical milling cutter is established based on the differential geometry and the enveloping theory. In the finish machining of helical milling cutter, the form grinding wheel profile is firstly derived. To reduce the cost and lead time of the generating method with the form-mill cutter for semi-finish machining, a toolpath generating method which combines the advantages of the generating method and sculpturing method was presented. The cutter location uses ball-nose conical end mill is derived according to the geometric characteristics of the enveloping element. The cutting simulations with solid model were performed to verify the proposed toolpath generation method.