在五坐标数控机床上对复杂模具曲面的高效加工

把微分几何中曲线与曲面之间的“切触”概念应用于流线型复杂曲面的数控加工,提出用圆柱铣刀和圆锥盘铣刀的外圆在五坐标联动中加工三维自由曲面的最佳切触条件。利用曲线与曲面之间可以比曲面与曲面之间贴合得更紧密的特点 ,把微分几何里的曲线与曲面之间的“切触”概念应用于曲面数控加工     

复杂曲面的简易高效数控加工

1　引言文献 [1]提出在五坐标数控机床上用盘状刀具加工复杂曲面的高阶切触原理 ,但五坐标机床属于高挡机床 ,本文提出巧妙方法 ,可在常用的三坐标机床上仍然实现高阶切触。2　用三坐标半加工复杂曲面加工任意曲面的情形如图 1所示 ,有三个坐标系。图 1　高效加工的坐标系1)固定坐标系 :ｘ( 0 ) ｙ( 0 ) ｚ( 0 ) 分别沿工作台纵向横向和铅垂方向 ,π( 0 ) 沿工件回转轴。2 )刀具坐标系 :ｏ(ｓ) 在铣刀底面中心 ,ｚ(ｓ) 为刀具轴线 ,ｘ(ｓ) ｙ(ｓ) ｚ(ｓ) 与ｘ( 0 ) ｙ( 0 ) ｚ( 0 ) 分别平行。3)工件坐标系 :ｘ( 1) 与ｘ( 0 ) 重合 ,绕ｘ( 0…     

五坐标加工步长计算

五坐标曲面加工的理论刀具轨迹是由刀具与零件曲面的啮合关系所确定的非线性连续曲线，由此而得的机床各运动轴的理想联动规律是复杂的非线性关系，但由于目前的CNC在多轴联动控制时，一般只具有线性插补功能，理论的非线性连续曲线只能以一系列小线性段进行离散逼近后，再由CNC机床控制各运动轴作五维线性插补来实现被加工曲面的近似包络成型，由此而导致原理性的加工误差，在数控加工中，刀具在机床坐标系下的运动根据与被加工曲面的相对关系有二个方向，一是走刀轨 迹的方向，称为走刀方向，其在此方向上在一个插补周期内所移动的距离称为走刀步长。另一个是在走刀轨迹增量的方向，称为切削带步长，下面讨论这两个方向刀具的所能够移动的距离与误差的关系和进行计算。     

自由曲面五坐标数控加工中几个关键问题的研究

自由曲面用平头立铣刀五坐标数控加工可以明显地提高切削效率和零件表面质量,但无干涉刀位产生一直是个难以解决的问题,本文对其中的几个关键问题进行了研究,导出了平头立铣刀的有效切削半径的一种计算方法,给出了自适应走刀步长度算法和切削行距的计算公式,最后给出了无干涉刀位生成方法,并用实例验证了方法的可行性,为提高加工效率和精度提供了有效途径。     

五坐标数控加工后置处理算法的研究

介绍了五坐标数控机床的后置处理原理，以cincinnati MilacronH5—800卧式加工中心为例，给出了针对转动坐标分别由回转工作台和主轴摆动实现的五坐标后置处理算法，并在该加工中心上得到验证。     

复杂曲面多轴数控加工非线性误差理论分析及控制

针对复杂曲面通常采用的多轴数控加工方式，结合加工用刀具，建立了多轴数控加工的非线性误差的数学模型，分析其影响因素，并给出了有效减少非线性误差的控制方法。     

用数控回转台加工圆柱面上曲面的编程方法

数控机床加工的零件轮廓一般由直线、圆弧组成 ,对于一些非圆曲线轮廓则用直线或圆弧去逼近 ,然后按各线段的数据编写程序。目前 ,国内许多中低档数控机床由于经费问题 ,常常没有配备相应的编程软件 ,因而一些曲面加工变得比较麻烦。而且从一些编程软件所编制的插补程序来看 ,一个简单的曲面需要数十Ｋ的空间。机床的存储空间往往不够一个程序用。若没有加工的后置软件的话 ,机床难以运行这些程序。作者在实际操作中 ,从前常常因为编制一个程序而耽误好几天时间 ,后来在程序中使用变数指令、巨集程式等数控语言 ,问题就迎刃而解。程式中位址…     

自适应加工技术在大型复杂曲面加工中的应用研究

根据复杂曲面的表面曲率变化情况,划分不同的加工区域,按照步长和曲率、行距和曲率的代数关系,采用自适应加工技术,适时调整步长和行距大小,提高了进给速率和加工效率,优化了大型复杂曲面的加工方案.     

UG二次开发在三阶切触加工刀位规划中的应用

非球头刀五轴数控加工可以通过调整刀具姿态,使得在刀触点处刀具包络曲面充分逼近理论设计曲面,从而显著提高给定精度下的切削带宽.研究了非球头刀宽行五轴加工自由曲面的三阶切触法,通过UG API几何造型的方法,精确计算切削带宽,并利用UG二次开发实现了平底刀加工自由曲面的刀位规划.算例结果表明该软件系统生成的刀具路径能显著提高加工效率.     

基于UG负角度曲面零件的三轴数控加工

用实际案例阐述了基于UG采用三轴数控机床对负角度曲面加工的方法,利用该方法能显著提高生产效率,保证加工零件的表面质量,降低加工成本及缩短生产周期。     

Enhanced virtual machining for sculptured surfaces by integrating machine tool error models into NC machining simulation

Sculptured surface machining is a time-consuming and costly process. It requires simultaneously controlled motion of the machine axes. However, positioning inaccuracies or errors exist in machine tools. The combination of error motions of the machine axes will result in a complicated pattern of part geometry errors. In order to quantitatively predict these part geometry errors, a new application framework ‘enhanced virtual machining’ is developed. It integrates machine tool error models into NC machining simulation. The ideal cutter path in the NC program for surface machining is discretized into sub-paths. For each interpolated cutter location, the machine geometric errors are predicted from the machine tool error model. Both the solid modeling approach and the surface modeling approach are used to translate machine geometric errors into part geometry errors for sculptured surface machining. The solid modeling approach obtains the final part geometry by subtracting the tool swept volume from the stock geometric model. The surface modeling approach approximates the actual cutter contact points by calculating the cutting tool motion and geometry. The simulation results show that the machine tool error model can be effectively integrated into sculptured surface machining to predict part geometry errors before the real cutting begins.     

自由曲面平头立铣刀五轴数控加工轨迹的计算方法

提出了一种在参数坐标系下自适应步长和行距的计算方法 ,该算法考虑了不同刀具接触点处的曲率差异 ,在满足加工精度和粗糙度的前提下 ,又能有效地提高加工效率。该算法适合加工汽车车身模具等曲率变化大的曲面。文中还给出了刀位计算公式。     

基于MasterCAM V9的四轴数控加工应用

MasterCAM V9是目前应用最广泛的CAD/CAM软件之一,它提供的四轴加工功能可实现复杂零件的高效、高精度加工。通过一飞机模型机头铜电极零件的实际制造过程,详细介绍了MasterCAM V9应用四轴加工功能的数控编程步骤,内容涉及加工工艺分析、加工参数设定、粗、精加工编程、后置处理和直接传输加工等。四轴加工简化了零件装夹工艺,缩短了加工辅助时间,提高了生产效率,改善了零件的加工质量。     

Static rigid force model for 3-axis ball-end milling of sculptured surfaces

Static rigid force model is used to estimate cutting forces of sculptured surface in a straightforward way, without considering tool deflection, machine tool dynamic behavior and any vibration effects. Two programs were used for calculations, “ACIS” the 3-D geometric modeler and “VISUAL BASIC”. Two programs were edited and used to perform the calculations, the scheme program to model the work piece, tool and cutting edge and to obtain the geometric data and the VISUAL BASIC program design to use ACIS geometric data to calculate the cutting forces. The engaged part of the cutting edge and work piece is divided into small differential oblique cutting edge segments. Friction, shear angles and shear stresses are identified from orthogonal cutting database available in literature. The cutting force components, for each tool rotational position, are calculated by summing up the differential cutting forces. Laboratory tests were conducted to verify the predictions of the model. The work pieces were prepared from CK45 steel using an insert-type ball-end cutter. No coolant was used in any of the experimental works. The cutting forces predicted have shown good agreement with experimental results.     

Spiral cutting operation strategy for machining of sculptured surfaces by conformal map approach

Although compound surfaces and polyhedral models are widely used in manufacturing industry, the tool path planning strategies are very limited for such surfaces in five-axis machining and high speed machining. In this paper, a novel conformal map based and planar spiral guided spiral tool path generation method is described for NC machining of complex surfaces. The method uses conformal map to establish a relationship between 3D physical surface and planar circular region. This enables NC operation to be performed as if the surface is plat. Then through inversely mapping a planar spiral defined by a mathematical function into 3D physical space, the spiral cutter contact paths are derived without inheriting any corners on the boundary in the subsequent interior paths. The main advantage of the proposed method is that a smoother, longer and boundary conformed spiral topography tool path is developed. Therefore, the machined surface can be cut continuously with minimum tool retractions during the cutting operations. And it allows both compound surfaces and triangular surfaces can be machined at high speed. Finally, experimental results are given to testify the proposed approach.     

用圆柱铣刀加工带冠弯扭叶片

本文把微分几何中曲线与曲面之间的“切触”概念应用于叶片复杂曲面的数控加工，提出用圆柱铣刀的外圆在五坐标联动中加工小曲率曲面的最佳切触条件。     

The analysis of correlative error in principal axis method for five-axis machining of sculptured surfaces

Correlative error is a kind of error between the cutter locations. This text presents a detailed analysis about correlative error in the principal axis method (PAM) that is a strategy of tool positioning for five-axis machining. It points out all the strategies based on linear projection cannot avoid this interference and cannot be disregarded especially in the strategies with large stepover. Accurate calculating is made individually on linear and curve feed and formulae are developed. The author also gave the available application range of PAM and the algorithm for estimating correlative error.     

Feed rate optimization for 3-axis ball-end milling of sculptured surfaces

The aim of this research is to improve the productivity of CNC machine tools by optimizing feed rate. To optimize feed rate two programs were used: “ACIS” (with scheme language) and “Visual Basic”. The scheme program for modeling the work piece, tool, cutting edge, and calculating maximum cutting force and the Visual Basic program to control all the activities linked to the ACIS program for estimating optimized feed values. Laboratory tests were conducted to verify the results from the modeling, using an insert-type one-flute ball-end cutter on a CK45 carbon steel work piece. No coolant was used throughout the experimental works. Comparisons were made between the maximum cutting forces, in the “fix” feed rate tests. The results indicate significant increases in productivity, which can be achieved, by using the optimized feed rate method.     

数控加工中组合曲面的离散化

提出了一种组合曲面的离散化方法 ,该方法充分考虑了数控加工的特点和要求 ,在满足数控加工精度的情况下尽量简化离散算法以提高组合曲面离散的效率 ,从而为数控加工组合曲面的实时插补提供了坚实的基础