组合型和插入型位置度功能量规的设计

介绍了组合型和插入型位置度功能量规结构的设计和使用方法,介绍了量规元件定位销、检验销、检具体、衬套、插销的设计;阐述了量规的技术要求和零件的验收方法。     

孔位置度综合量规的设计方法与应用

在零件的制造过程中,需快捷地测出孔的位置度是否符合要求.结合用于重型卡车12L发动机水泵壳体位置度检测的综合量规设计,分析了孔位置度检测方法的特点、确定原则及区别,探讨了综合量规的设计方法及步骤,即工作部位结构的设计,测量要素的尺寸选择,分析与计算.     

孔位置度综合量规设计计算的一种新方法

针对实际生产中某些零件中孔直径的公差较大 ,而位置度要求较高这一特点 ,提出了设计孔位置度综合量规的一种新方法     

波导法兰盘位置量规设计

本文介绍了两种确定波导法兰盘位置量规尺寸与公差的方法,重点从量规测量造成的“误判”角度综合考虑使用性能与工艺要求的关系来叙述尺寸、公差计算方法,并分析了各方法的利弊,提出修正的设计方案。     

汽车制动器底板孔位置度综合量规设计与应用

实际生产中一种汽车制动器底板的基准孔直径公差较大,而被测孔位置度要求较高,针对这一特点文中提出了设计孔位置度综合量规的一种设计方法,实际应用证明该量规对提高产品质量与经济效益有一定的现实意义。     

检验轴承杯法兰孔位置度误差的功能量规设计

针对一齿轮减速箱中的轴承杯零件图上标注的法兰孔的位置度公差,详细介绍了检验零件法兰孔位置度误差的专用功能量规设计过程,为此类功能量规的设计提供了参考。     

对盘类零件均布键的位置度标注的分析及其位置量规的设计

我厂盘类零件均布键的位置度至今仍采用角度尺寸公差的标注形式来体现。这种标注方法存在着一定的不足：即被测要素的位置度要通过计算后方能确定公差值．其图样不醒目，给位置量规的设计带来不必要的麻烦。图1是我厂产品的静盘骨架的零件图．该零件有12个内键，每个键的中心平面的变动范围在4′之内．12个键的中心平面的积累误差应在±4′之内。按照图样的标注．12个键的中心平面的位置度公差带如图2所示：从图2可看出12个键的公差带均为扇形技体，其高度应为零件的厚度（3mm）。零件的这部分要素为近似矩形，其中心要素的变动范围直接受外…     

位置量规设计中的相似原理

GB8069—87《位置量规》于1988年7月1日正式实施。《位量置规》国家标准是实施GB1182～1184—80《形状与位置公差》的重要技术保证和必不可少的配套标准。《位置量规》标准的贯彻,对一般工程技术人员来说,按照标准的规定,设计计算量规工作部位的尺寸并不困难。但是,在当前位置量规结松设计方面的     

形位公差代号标注方法的研究（之三）

1　被测要素指引线的位置和指向(1)被测要素指引线末端箭头指向轮廓线时,被测要素可能是相应的面,也可能是面上的素线或横截圆周。可能发生误解时必须作出特别的说明[如图1b)]。没有文字说明时,人为约定理解为面[见图1a)]。a)b)图1(2)当被测要素是中心要素时,GB1182-80允许将指引线注在相应中心线上,GB/T1182-1996则只规定了将指引线注在相应宽度(直径)尺寸线的延长线上的标注方法。后者之所以如此规定,无非是为了避免因共用中心线而导致误解。笔者以为,在不致引起误解的前提下(例如实芯圆轴轴线的直线度),将指引线标注在中心线上的做法仍…     

形位公差的标注应注意的问题

形位公差的在图样上正确标注,可以准确地说明被测要素的形位和公差要求.形位公差的标注对于初学者而言不好理解,经常出现标注错误.笔者对形位公差标注中常出现的一些问题进行了分析与阐述,特别是被测要素与基准要素的正确标注进行了较为透彻的说明,对于初学者有较好的指导意义.     

A C++ library for the automatic interpretation of geometrical and dimensional tolerances

In rough machining of parts with sculptured surfaces, two main objectives are usually considered: machining time and overall removed material at the end of the roughing phase. The outcome of that phase is critical for the subsequent finishing phase. This paper proposes a method for measuring roughed part quality through calculation of the local difference between the roughed part geometry and the ideally finished part geometry. The method calculates the height from a point lying on the roughed surface to its projection on the ideally finished part surface. Using the API of a CAD system for this purpose proves computationally inefficient. Therefore, a mean distance between a triangle of the roughed surface triangular mesh and the ideally finished part surface region lying in a suitable envelope is calculated instead. The calculation is repeated not for all triangles of the mesh, but for a sample as low as 3%, which, according to the Levene statistical test suffices, thereby, reducing computational cost by orders of magnitude. The method ultimately yields a single figure, i.e. the standard deviation of local differences between the roughed and finished part, normalized by the mean difference. The concept was tested on sculptured surface parts of various mechanical and operational properties and was proven efficient in all test cases.     

对位置度公差采用独立原则标注的浅见

GB/T 4249—1996《公差原则》规定了独立原则和相关要求,相关要求又分为包容要求、最大实体要求和最小实体要求。在实际应用中选用公差原则有着非常重要的意义,选用得不恰当会给零件的加工、检测和装配带来一定的难度。下面举例来说明。 图1是我厂的一个刹车盘的图样,该零件的6×φ8 H7均布孔对基准轴线A的位置度采用了独立原则,各个被测孔的轴线必须位于直径为公差值φ0.03mm且相对于基准轴线的理论正确尺寸所确定的理想位置为轴线的圆柱面内。其公差带图如图2所示。 图1 刹车盘零件图 图2 位置度公差带…     

基于小位移旋量的公差模拟建模及公差分析

公差分析是产品规范设计的重要内容,影响产品最终性能。研究了小位移旋量的公差建模方法,随机取值模拟配合表面在公差域内的变动。沿装配路径,采用齐次坐标逐步变换求解装配体封闭环相对全局坐标的变动,进行了三维公差分析,利用一定规模的模拟样本表现累积误差的分布形式。用实例验证了方法的有效性。     

虚公差问题的研究

本文根据实际生产情况,首次提出虚公差概念,指出虚公差的意义,并在虚公差概念的基础上提出由尺寸链基本公式和概率法求解带补偿件的装配尺寸链的基本原理,从而解释了G／T5847－1986《尺寸链计算方法》为什么对有补偿件的尺寸链不推荐“概率法”的真正原因,没有虚公差概念,对于带补偿件的尺寸链来讲,不可能有真正意义的概率法。     

Cams and manufacturing tolerances

In a cam mechanism the actual output is affected firstly by the inertia and elasticity of the follower train and secondly by manufacturing tolerances. The error, ie the difference between the actual output and the desired output, due to the first cause is termed the flexibility error¹ and that due to the second cause is termed the mechanical error. This paper suggests a method to minimise both types of errors in a cam mechanism. A numerical example is included to illustrate the application of the method     

Part optimization and tolerances synthesis

A tolerance synthesis provides the distribution of tolerances on the functional specifications of parts for a mechanism, with the objective of satisfying a set of functional requirements. This approach involves adjusting the nominal dimensions of parts. The present article offers a six-step solution within an Excel solver environment. The designer is able to control the optimization process using a dashboard. The initial steps detect conflicting requirements and suggest compromises, while the subsequent steps optimize the nominal part dimensions in order to maximize mechanism quality with minimum tolerance. The final steps then seek to maximize tolerances with the aim of minimizing costs. The proposed method can also manage specifications with both maximum and minimum material requirements.     

Modelling of tolerances and manufacturing dimensions

To obtain imposed dimensional and geometrical specifications for any mechanical piece, production tolerances must be calculated. So a simulation of workpiece behavior when it is machined, has permitted calculations of deviations on machined surfaces.The method of deviation calculation is based on a comparison between imposed functional tolerance and the tolerance calculated in relation to deviations on two machined surfaces or between a machined surface and the operational datum.The one direction modelling of deviations inquires practical inputs such as the planning process, the operational datum, the deviations on rough surfaces, and deviations on surface datum for any stage of machining. The developed method allows determining the deviations on machined surfaces. Then, tolerances on production dimensions were calculated in three directions. These results have permitted to define average production dimensions, which may be used for NC machine programming and to prepare an optimal rough piece configuration.The developed method has been applied for the machining of a fixing screw.     

Evaluation and uncertainty analysis of vectorial tolerances

Recently, the integration of coordinate measuring machines (CMMs) and computer-aided design (CAD) systems has promoted a new approach to the evaluation of workpiece geometry; namely, vectorial dimensioning and tolerancing. This new approach is promising, because it defines process-related dimensions and tolerances clearly and distinctly. Therefore, it enables proper manufacturing control and process diagnosis. However, current proposal of vectorial tolerancing has several limitations. First, the current orientation vector is inadequate for representing true three-dimensional (3D) orientation. As a result, the orientation of a free-form surface cannot be properly established. Second, there has been little discussion of vectorial tolerance evaluation. This paper proposes a new rotation vector that provides a more general mathematical basis for representing vectorial tolerances. A nonlinear, best-fit algorithm has been developed to evaluate vectorial tolerances for both analytical geometric elements and free-form surfaces. To study the uncertainty of the best-fit result caused by sampling strategy and dimensional errors, sensitivity analysis of the evaluated parameters was investigated. Simulation and experiment showed that the developed model can predict the uncertainty of the evaluated parameters accurately.