公差实验在教学中的应用

公差实验课是高等院校机械类、仪器仪表类专业必修的专业基础实验课程，机械专业不同于其他学科，理论知识固然重要，但更多的要注重实践。本文分析了传统教学模式的弊端与不足，介绍了公差实验教学体系改革的新思路。     

端面垂直度、轴向圆跳动及轴向全跳动关系探讨

几何公差分为形状公差、方向公差、位置公差、跳动公差四种类型，相互间具有一定的关系，文章以端面垂直度公差、轴向圆跳动公差、轴向全跳动公差为例，在明确各公差项目含义的基础上，从公差带及应用上论述了相互间的关系，对更好的理解几何公差具有引导的作用。     

冲压模具精加工分析

模具制造，精加工阶段采用的方法一般采用磨削，电加工及钳工处理，形状公差及尺寸精度等许多技术参数，在具体的生产中，操作困难较多，但还是有一定的经验保证方法。     

公差查询及标注系统的设计

介绍在 Auto CAD平台上开发公差查询及标注系统实用软件。软件包括 :按照最新国家标准设计而成的形位公差查询及标注、尺寸公差查询及标注、表面粗糙度查询及标注等。     

谈“公差原则及其应用”

１公差原则的基本知识公差原则是处理尺寸公差和形位公差关系的基本依据，包括独立原则和相关要求，如下所示：公差原则独立原则相关要求包容要求最大实体要求最小实体要求可逆要求１１独立原则独立原则是指图样上给定的尺寸公差和形位公差两者之间相互无关，应分别满足...     

面向质量目标的统计公差技术的发展及其标准化的系统构想

本文简要地介绍了统计公差技术和标准在国内外发展的概况.针对质量控制领域在学术上的新发展,为了满足企业需求,统计公差技术应该有所创新和发展,其如统计公差技术成为联系设计规范、质量目标和过程质量控制三个层面的不可缺少的标准化界面并能真正地在工业实践中应用.本文还讨论了面向质量目标的统计公差及其标准化的构想,面向质量目标的统计公差的建模、面向质量目标的统计公差的置信区间的计算以及统计公差标准的应用等问题.     

重要国家标准的制订与宣贯（74）──审查通过的十六项新国家标准介绍

重要国家标准的制订与宣贯（７４）──审查通过的十六项新国家标准介绍技术制图圆锥的尺寸和公差注法本标准等效采用ＩＳＯ３０４０—１９９０，其特点是为了使二同轴锥面（圆锥要素的最大实体周寸和最小实体尺寸）形成两个具有理想形状价包容面（公差带），采用了面轮廓...     

密封的改进

我厂为气缸盖的专业生产厂家，气缸盖在工作时需在温度较高的环境下进行，需要水冷却和全损耗系统用油润滑，所以有冷却水孔和油眼孔，在加工组装时，需要密封。密封孔一般在φ１２ｍｍ以下，如果采用铝堵密封，在装配时需涂密封胶，不易找正，砸堵时容易偏斜，破坏密封孔。另外铝堵件小，批量不算太大，所以价格贵，密封孔的尺寸公差也要求比较严，一般为Ｈ７，需要精加工才能达到要求。 而若改用小钢球密封，钢球由于是标准件，容易采购，价格低，装配时容易找正，密封孔和钢球的过盈量为 ０．２～０．２５ ｍｍ，密封孔的尺寸公差为Ｈ１…     

发动机凸轮单程段检测方法初探

介绍的检测方法，既保证了凸轮升程误差最小包容区域的形状和公差带形状一致，又使升程最大误差最小，从而避免了凸轮检测评定中的误判。     

发动机单程凸轮升程误差的评定方法

针对发动机凸轮升程公差具有形状公差和尺寸公差的双重属性 ，以及升程公差有分段要求的特殊性，提出了确定单程凸轮理想检测位置的方法和评定单程凸轮升程误差的方法。这种方法与凸轮单程设计要求相一致。     

有关Cpk公式的12个错误观点剖析

在发现过程能力指数4个基本特性并提出对称公差过程能力指数修正公式Cpk基础上，文章对质量界广为流行的有关Cpk的12个典型错误观点进行了剖析。     

前束一致性的控制方法分析

由于硬点坐标参数容差引起的,汽车悬架外特性参数随轮跳变化曲线的变化称为汽车悬架外特性的一致性,它是评价一种汽车产品整体质量一个重要指标。目前,还没有文献提出汽车悬架外特性一致性的具体控制方法,在汽车动力学软件中也没有汽车悬架外特性参数一致性分析的模块。所以,本文旨在利用区间数学的方法建立其一致性分析的数学模型,并用影响其一致性的硬点坐标参数容差作为区间参数,最后用区间分析方法计算其一致性结果。通过使用这种方法对双横臂独立悬架模型的前束角一致性进行分析,证明了区间分析方法计算汽车悬架外特性的一致性是可行的。     

The C”<Subscript>pk</Subscript> index for asymmetric tolerances: Implications and inference

The process capability index C_pk has been widely used in the manufacturing industry to provide numerical measures on process performance. Since C_pk is a yield-based index which is independent of the target T, it fails to account for process centering with symmetric tolerances, and presents an even greater problem with asymmetric tolerances. Pearn and Chen (1998) considered a new generalization C_pk which was shown to be superior to other existing generalizations of C_pk for processes with asymmetric tolerances. In this paper, we investigate the relation between the fraction nonconforming and the value of C_pk. Furthermore, we derive explicit forms of the cumulative distribution function and the probability density function for the natural estimator _pk, under the assumption of normality. We also develop a decision making rule based on the natural estimator _pk, which can be used to test whether the process is capable or not.     

Econometric software reliability and nonlinear estimation in EViews: comment

A recent software review in this journal (McCullough, 1999 ) raises serious questions about EViews' performance on nonlinear least squares problems. We demonstrate that after correcting errors in the paper and adjusting convergence tolerances, EViews performance was comparable with the other benchmarked software. Copyright © 2000 John Wiley & Sons, Ltd.     

零件设计中形位公差项目的选择

在进行零件设计时,正确选择形位公差项目及其公差值的确定是一项很慎重的工作,既要根据零件的使用性能和互换性要求,又要考虑生产率和成本的高低。本文仅对形位公差项目的选择进行初步的探讨。     

Over toleranties on passingen in den machinebouw

Tolerance problems in mechanical engineering ought to be treated with statistical methods.
It is shown that the use of range (instead of standard deviation) for measuring variability in tolerances and fits leads to systematic errors.
The suggestion is made to measure variability in mechanical engineering by T = 4,65 , being the 98%-range in the case of normal distribution.
A simple statistical approach to selective assembling is mentioned.     

A new method for automatic synthesis of tolerances for complex assemblies based on polychromatic sets

In computer-aided tolerance design (CAT), integrated design of dimensional and geometric tolerances is still one of the research hotspots. Polychromatic sets theory (PST) is a new mathematic tool, which is especially suitable for formal hierarchical structure models. Based on PST, in this article, a new hierarchical representation model for tolerance synthesis is presented to realise integrated design of dimensional and geometric tolerances. According to the inference relations between unified and individual colours of PST, the synthesis matrices of variational geometric constraints (VGC) are established in the VGC tier of the model, and the synthesis matrices of tolerance types are established in the tolerance type tier of the model. On this basis, the synthesis processes from the feature tier to the VGC tier and from the VGC tier to the tolerance type tier can be realised. VGCs, which are achieved by the synthesis matrices of VGCs, can be combined together to establish a well-constrained VGC network (VGCN). Tolerance types, which are achieved by the synthesis matrices of tolerance types, can be added to the well-constrained VGCN to construct a well-constrained tolerance network. An application example is given in the article to illustrate the synthesis steps.     

Estimating process capability index C′′pmk for asymmetric tolerances: Distributional properties

Pearn et al. (1999) considered a capability index C ^′′ _pmk, a new generalization of C _pmk, for processes with asymmetric tolerances. In this paper, we provide a comparison between C ^′′ _pmk and other existing generalizations of C _pmk on the accuracy of measuring process performance for processes with asymmetric tolerances. We show that the new generalization C ^′′ _pmk is superior to other existing generalizations of C _pmk. Under the assumption of normality, we derive explicit forms of the cumulative distribution function and the probability density function of the estimated index . We show that the cumulative distribution function and the probability density function of the estimated index can be expressed in terms of a mixture of the chi-square distribution and the normal distribution. The explicit forms of the cumulative distribution function and the probability density function considerably simplify the complexity for analyzing the statistical properties of the estimated index . Received April 2000     

Estimating and testing process accuracy with extension to asymmetric tolerances

Pearn et al. (Commun. Stat. Theory Methods, 27(4):985–1000, 1998) introduced the process accuracy index C _a to measure the degree of process centering, the ability to cluster around the center. In this paper, we derive an explicit form of the cumulative distribution function for the estimator [^(C)]_a{\hat{C}_a } with the case of symmetric tolerances. Subsequently, the distributional and inferential properties of the estimated process accuracy index C _a are provided. Calculations of the critical values, P-values, and lower confidence bounds are developed for testing process accuracy. Further, a generalization of C _a for the case with asymmetric tolerances is proposed to measure the process accuracy. Based on the results practitioners can easily perform the testing of the process accuracy, and make reliable decisions on whether actions should be taken to improve the process quality. An application is given to illustrate how we test the process accuracy using the actual data collected from the factory.     

A response surface approach to tolerance design

In spite of Taguchi's robust parameter design (Introduction to quality engineering: designing quality into products and processes, 1986, Asian Productivity Organization, Tokiyo), tolerance design is still important at the design stage of products and processes. Taguchi's proposal and related methods for tolerance design, however, do not efficiently use the information that can be obtained from the parameter design experiment. In this paper, we introduce a new method for tolerance design based on the response surface approach to parameter design. It is a flexible method because non-normal distributions of the noise factors and the quality characteristic are allowed. Moreover, it is unnecessary to perform a new physical experiment. Essentially, tolerances of noise factors are maximized, subject to constraints to ensure that the mean value of the quality characteristic remains on target and the fraction nonconforming is below a pre-specified maximum. Some aspects of model uncertainty are discussed and the method is illustrated by means of an example.