浅淡数控机床对刀与坐标的关系

通过对对刀方法和原理及对刀步骤的分析,确定工件坐标系和机床坐标系关系,从而确认了它们相对的位置.从而简化了数值计算,方便了编程.     

定位误差计算的矢量法（上）

六点定则只解决了工件的宏观定位精度问题,要完全解决工件的定位精度,还必须研究与解决工件的微观定位精度问题,即必须针对工件某特定的具体表面进行研究,研究它们的位置误差及基准不重合误差对某加工表面的尺寸和相互位置等方面造成的影响,即必须研究工件的定位误差及其计算问题。本文介绍用矢量法对定位误差进行计算。具体将按单基准定位及组合定位这两种最典型的情况进行讨     

数控机床对刀方法

在数控机床加工中,刀具刀位点的运动轨迹自始至终需要在机床坐标系下进行精确控制,但编程尺寸却是按人为的工件坐标系确定的,工件坐标系确定之后,还需要确定刀位点在工件坐标系中的位置,这样,工件坐标系与机床坐标系之间的相对位置关系就确定了,这一过程称为对刀。数控机床加工中经常涉及到对刀问题,对刀问题处理的好坏,直接影响到加工零件的精度和数控机床的操作。我们所说的对刀,包含两方面：一是刀具偏置参数的测量与输入,二是对刀点的确定。     

加工中心对刀后数值的处理

在数控机床上加工零件,刀具与工件的相对运动是以数字形式来体现的,因此必须建立相应的坐标系,才能明确刀具与工件的相对位置。数控机床有两种坐标系：机床坐标系和工件坐标系。机床坐标系是生产厂家设定的固有坐标系,一般是通过开机后回参考点建立。     

对使用工夹模具时产生定位误差的分析

在生产实践中，应保证零件的加工精度，其尺寸精度是由机床调整或定尺寸刀具保证，形状精度由机床精度或刀具精度决定，而位置精度则主要取决于零件的定位及夹具和机床的精度。定位误差就是指工件在夹具中定位时，由于工件的位置偏离了理想位置而引起的加工误差。工件在夹具中的定位，实际上是以定位元件、工件的定位基准面来代替夹具原理中的“定位原理”所决定的点、线、面。但由于定位元件和工件的定位基准面均有制造误差，因而就使工件在夹具中的实际定位位置，将在一定范围内有所变动，也就是存在着一定的定位误差。所以我们在加工中应…     

机器人视觉技术在电路贴装生产中的应用研究

根据腔体类工件电路贴装的生产现状,构建了一套移动式机器人视觉系统,结合工件图像特点设计了合理的图像处理算法与处理流程,实现了工件坐标系、视觉坐标系及机器人工具坐标系的可靠转换与绑定,建立了可自动校正电路与壳体位置误差的关系,达到了"看得清"、"取得准"、"放得好"的目的。针对电路拾取与壳体贴装中可能出现的反光、超差问题,提出了切实可行的解决办法,在实际生产中得了较好的验证。     

夹具定位误差分析自动建模方法

提出一般夹具的定位误差分析模型建立方法。根据工件—夹具系统的误差形成和传递路线分析,将工件—夹具系统分为定位元件、定位基准、工序基准和加工特征等四个要素组成,通过求解四个要素之间的位置变动获得工件—夹具系统整体的定位误差。将四个要素之间的位置及其变动关系用连杆机构模型等价表示,工件—夹具系统转换为接触副等价机构、公差关系等价机构、工序尺寸等价机构等三个等价机构的组合。研究工件和夹具定位元件接触副与等价机构之间的映射关系的建立方法,研究定位基准与工序基准、工序基准与加工特征之间的尺寸与公差关系所对应的等价连杆机构的建立方法,研究采用机构的结构参数和运动参数表示工件—夹具系统的所有工序信息及其内在联系的方法。利用机构学的机构位置计算方法求解定位误差,实现定位误差分析的自动化。     

工件的视觉定位及机器人控制的应用研究

机器人通过视觉对工件定位信息和工作环境进行分析,完成相关工作任务成为机器人发展的方向.论文通过双目相机的开发平台Triclops SDK进行二次开发,在PC上实现了机器人对工件位置信息的快速获取;通过ABB机器人控制软件Robotstudio以及PC SDK的二次开发,实现对机器人的控制;研究了以公共点为基础的七参数法,采用标定件的方式实现了相机-机器人坐标系的标定.实验证明了系统的可行性和有效性.     

机械加工夹具浮动支撑定位装置的设计

针对实际生产中尺寸不稳定的毛坯,设计了一种结构独特、操作简单的浮动支撑定位装最垂可根据工件毛坯具体尺寸而有效调整支撑柱的位置,保证支撑柱可与工件毛坯接触,从而保证工件毛坯能被准确夹紧定位及后工序的有效进行。     

用CAD的尺寸标注功能来确定机床夹具的定位误差

工件在加工时,首先应在机床夹具上定位。由于工件定位基准与夹具定位元件的尺寸制造误差及其配合间隙、定位基准与工序基准不重合、工件以多基面定位时基准之间的位置误差这三种原因,引起工序基准在工序尺寸方向上的最大位置变化量即定位误差。定位误差极     

主减速器壳体车削工装夹具设计

针对主减速器壳体在立式多刀半自动车床上加工时,采用标准液压三爪卡盘无法有效定位夹紧工件的问题,依据工件的结构特点,设计制造一种能在一次装夹下完成粗精两序加工的专用车削工装夹具,彻底解决了由于多刀同时粗加工、车削抗力大,工件夹持不可靠的安全问题。通过夹紧力的高低压转换,有效防止工件夹紧变形。生产实践证明,该夹具简单可靠,便于操作,提高了生产效率,保证了加工精度。     

建立数控工件坐标系的方法综述

工件坐标系的建立,是数控编程和数控加工的一项重要内容,它对于简化编程数学计算,方便加工、减少加工误差,提高加工精度,都具有十分重要的意义。本文结合生产实际,针对建立工件坐标系,进行了一些具体的研究,对数控编程和数控加工有较大的指导意义。     

Machining fixture layout design using ant colony algorithm based continuous optimization method

In any machining fixture, the workpiece elastic deformation caused during machining influences the dimensional and form errors of the workpiece. Placing each locator and clamp in an optimal place can minimize the elastic deformation of the workpiece, which in turn minimizes the dimensional and form errors of the workpiece. Design of fixture configuration (layout) is a procedure to establish the workpiece–fixture contact through optimal positioning of clamping and locating elements. In this paper, an ant colony algorithm (ACA) based discrete and continuous optimization methods are applied for optimizing the machining fixture layout so that the workpiece elastic deformation is minimized. The finite element method (FEM) is used for determining the dynamic response of the workpiece caused due to machining and clamping forces. The dynamic response of the workpiece is simulated for all ACA runs. This paper proves that the ACA-based continuous fixture layout optimization method exhibits the better results than that of ACA-based discrete fixture layout optimization method.     

对刀建立工件坐标系在数控加工与数控编程中的应用

对刀建立工件坐标系是数控加工操作的重要内容.正确的对刀操作,建立工件坐标系,编制符合加工工艺要求的数控程序,这是零件加工精度的保证,也是实现数控机床高精度和高效率的基本要求.从数控加工的对刀技术与程序编制的理论要求和实际应用两个方面进行了分析与探讨.     

Analysis of Reactions and Minimum Clamping Force for Machining Fixtures with Large Contact Areas

This paper presents a model for analysing the reaction forces and moments for machining fixtures with large contact areas, e.g. a mechanical vice. Such fixtures transmit torsional loads in addition to normal and tangential loads and thus differ from fixtures using point or line contacts. The model is developed using a contact mechanics approach where the workpiece is assumed to be elastic in the contact region and the fixture element is treated as rigid. Closed-form contact compliance solutions for normal, tangential, and torsional loads are used to derive the elastic deformation model for each contact. A minimum energy principle is used to solve the multiple contact problem yielding unique predictions of the fixture–workpiece contact forces and moments due to clamping and machining forces. This model is then used to determine the minimum clamping force necessary to keep the workpiece in static equilibrium during machining. An example is given to demonstrate its effectiveness in analysing the clamping performance of a mechanical vice during machining.     

Fixture Clamping Force Optimisation and its Impact on Workpiece Location Accuracy

Workpiece motion arising from localised elastic deformation at fixture-workpiece contacts owing to clamping and machining forces is known to affect significantly the workpiece location accuracy and, hence, the final part quality. This effect can be minimised through fixture design optimisation. The clamping force is a critical design variable that can be optimised to reduce the workpiece motion. This paper presents a new method for determining the optimun clamping forces for a multiple clamp fixture subjected to quasu-static machining forces. The method uses elastic contact mechanics models to represent the fixture-workpiece contact and involves the formulation and solution of a multi-objective constrained oprimisation model. The impact of clamping force optimisation on workpiece location accuracy is analysed through examples involving a 3-2-1 type milling fixture.     

A Clamping Design Approach for Automated Fixture Design

In this paper, an innovative clamping design approach is described in the context of computer-aided fixture design activities. The clamping design approach involves identification of clamping surfaces and clamp points on a given workpiece. This approach can be applied in conjunction with a locator design approach to hold and support the workpiece during machining and to position the workpiece correctly with respect to the cutting tool. Detailed steps are given for automated clamp design. Geometric reasoning techniques are used to determine feasible clamp faces and positions. The required inputs include CAD model specifications, features identified onthe finished workpiece, locator points and elements.     

Optimal Fixture Design Accounting for the Effect of Workpiece Dynamics

This paper presents a fixture layout and clamping force optimal synthesis approach that accounts for workpiece dynamics during machining. The dynamic model is based on the Newton– Euler equations of motion, with each fixture–workpiece contact modelled as an elastic half-space subjected to distributed nor-mal and tangential loads. The fixture design objective in this paper is to minimise the maximum positional error at the machining point during machining. An iterative fixture layout and clamping force optimisation algorithm that yields the "best" improvement in the objective function value is presented. Simulation results show that the proposed optimis-ation approach produces significant improvement in the work-piece location accuracy. Additionally, the method is found to be insensitive to the initial fixture layout and clamping forces.     

Study on the influence of geometric errors in rotary axes on cubic-machining test considering the workpiece coordinate system

Evaluating the influence of geometric errors in rotary axes is a common method used by a five-axis machine tool for improving the machining accuracy. In conventional geometric error models, the table coordinate system is considered as the final workpiece coordinate system. In this study, an additional workpiece coordinate transformation was proposed to identify the influence of geometric error. First, a cubic machining test was conducted. Second, the necessity of workpiece coordinate transformation was analyzed, and a method for coordinate transformation was proposed. In addition, both machining simulation and an actual machining experiment of the cubic machining test were conducted to verify the efficiency of the proposed method. The results indicate that the workpiece coordinate transformation is an essential part of the geometric error model for accurately simulating the geometric error influence. The method for identifying the geometric error influence considering the workpiece coordinate transformation is applicable in manufacturing.     

基于线性规划的工件稳定性建模及其应用

工件在实现定位后,在加工过程中将要受到工件重力和切削力等外力的作用。为使工件保持定位精度与生产安全性,必须保证工件在整个加工过程中具有稳定性。系统地讨论了工件稳定性建模及其求解方法,在摩擦锥线性近似以及变量非负转换的基础上,提出了工件稳定性的定量判断准则;利用线性规划方法对工件稳定性模型进行分析。结果表明,稳定性模型不仅能够验证工件的稳定性,而且还能够分析夹紧力大小、作用点以及夹紧顺序的合理性。这种方法既适用于夹具夹持稳定性分析,也适用于机械手的抓取稳定性分析。