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1、Unit 14 Product Test and Quality ControlContentslNew Words&Expressions lText&TranslationlComplex Sentence AnalysislKey to ExercisesNew Words&Expressions lculmination klminein n.顶点lcontractual kntrktul adj.契约的ldeficiency difinsi n.缺乏，不足lquasi-static kweisaisttikadj.准静态的lhysteresis histri:sis n.滞后作用，(
2、物)磁滞现象lclearance fit 间隙配合linterference fit 过盈配合ltransition fit 过渡配合lliaison lieizn n.联络Text&Translationl1.Product Test lProduct test can be thought of as the culmination of all process control work.It can also be thought of as a quality check of the inspection process itself.If the quality plan is a
3、dequate and carried out properly,then the products performance should have been verified and a total test is redundant.For this reason,a test of the completed product is often nothing more than a contractual requirement that must be performed before the customer accepts the product.But product test
4、is also more than proving.And testing to whole is equal to the sum of the parts.Text&Translationl 1It allows for gathering data that support the design theory of the product,for interpretations to be made for further improvements in design so that future products will be better than present ones,and
5、 for evaluation of design evolution toward better performance costs.In addition,it is a means of verifying design,since not all design parameters can be fully calculated or predicted.Text&TranslationlProduct test engineers work closely with design engineers to provide useful data for testing.They mu
6、st also work in close harmony with engineers all other phases of manufacturing.Not infrequently,product testing will turn up deficiencies in design that requires major revisions in manufacturing processes.This is particularly true if the company produces many prototypes and has short production runs
7、.Therefore,manufacturing engineers are as interested in product tests results as design engineers.Text&TranslationlFor complex products,product test becomes a very important part of the total process control function.It gives the company a high degree of confidence that the product will perform as t
8、he customer expects it to,and this is a valuable marketing tool as it helps to establish the proper reputation with the customers.Text&Translationl2.Geometric Errors lGeometric errors are defined here as errors in form of individual machine components(e.g.,straightness of motion of a linear bearing)
9、.Geometric errors are concerned with the quasi-static accuracy of surface,which bear upon the moving relative of the surfaces.Geometric errors can be smooth and continuous(systematic)or they can exhibit hysteresis(e.g.,backlash)or random behavior.2Many factors affect geometric errors including:surfa
10、ce straightness(see Fig.14-1),surface roughness,bearing preload,kinematics versus elastic design principles and structural design philosophies.Text&TranslationFig.14-1 Straightness Errors Caused by Surface Form and Finish Errors Text&Translationl3.Fit and Tolerance lFit is defined as the relation re
11、sulting from the difference between the sizes of two mating parts.And tolerance is defined as the difference between the maximum limit and the minimum limit.The tolerance is also equal to the algebraic difference between the upper and lower deviations(see Fig.14-2).Text&TranslationFig.14-2 Diagram I
12、llustrating Basic Size,Deviations and Tolerances Text&TranslationlDepending upon the actual limits of the hole or shaft,a fit may be classified as follows:l(1)Clearance fit is a fit that always provides a clearance between the mating parts.In this case,the tolerance zone of the hole is entirely abov
13、e that of the shaft.l(2)Interference fit is a fit that always provides interference between the mating parts.Here,the tolerance zone of the hole is entirely below that of the shaft.l(3)Transition fit is a fit that may provides either a clearance or interference between the mating parts depending on
14、the actual dimensions of the finished products.Text&TranslationlA tolerance is designated by a letter(in some cases,two letters),a symbol,and a numerical symbol.Capital letters are used for holes and small letters for shafts.The letter symbol indicates the position of the zone of tolerance in relati
15、on to the zero line representing the basic size.The numerical symbol represents the value of this zone of tolerance and is called the grade or quality of tolerance.Both the position and the grade of tolerance are functions of the basic size.A size with tolerance is thus defined by its basic value fo
16、llowed by a letter and a number,e.g.,20H7 or 20g6.Text&TranslationlIn engineering drawing practice,the tolerance for hole and shaft is written a little above and little below the basic size,respectively.3Similarly,a fit is indicated by the basic size common to both the mating components,followed by
17、the appropriate symbols corresponding to each component.Text&Translationl4.Quality Planning lThis is the planning and strategy activity of process control,and is sometimes referred to as process planning or inspection planning.The engineers involved develop the plans for checking the adequacy of per
18、formance of shop operations to ensure that the final product performs as designed.Using plans and methods produced by measurement of productivity and work measurement(MP&WM)as a guide,quality-planning engineers determine where inspections and nondestructive tests will be specified during the manufac
19、turing process.They also specify the type of inspection or test to be conducted and,based on design engineering requirements,determine what will constitute acceptance or rejection.Text&TranslationlNormal manufacturing activities produce a certain percentage of deviations from drawing.Some are import
20、ant,some of little consequence.It is the quality planning engineers responsibility to evaluate these deviations and determine what the proper corrective action will be.They then ensure through MP&WM that the corrective actions are factored into manufacturing planning for rework.As the arbiter of qua
21、lity via the deviation from drawing procedure,quality planning has the database to evaluate performance of the various shop and support functions.A score-keeping function is possible and desirable;in this way quality planning can report to management whether quality levels are improving or declining
22、.Text&TranslationlQuality status can be reported by statistically evaluating the numbers of deviations and their seriousness.This leads naturally to an evaluation of the cost of doing the repair work caused by the deviation.Repair work,which constitutes manufacturing losses,is an important measureme
23、nt of organizational quality levels.Manufacturing losses are a significant measure of the adequacy of attention to detail of the operators and their foremen.High losses indicate a poorly managed operation.Quality planning engineers are responsible for setting the manufacturing losses,budgets,and mea
24、surements policy.Text&Translationl5.Quality Control lQuality control has traditionally been the liaison between manufacturing and design.This function interprets designs specifications for manufacturing and develops the quality plan to be integrated into manufacturing engineerings methods and planni
25、ng instructions to operations.Quality control is also responsible for recommending to management what level of manufacturing losses(cost of mistakes in producing the product)can be tolerated.This is based on the complexity of the product design;specifically the degree of preciseness necessary in tol
26、erances.Quality control traditionally monitors manufacturing losses by setting a negative budget that is not to be exceeded,and establishes routines for measurement and corrective action.Text&TranslationlWithin the past decade or two,quality control has become increasingly involved with marketing an
27、d customers in establishing documentation systems to ensure guaranteed levels of product quality.This new role has led to the new title quality assurance,to differentiate it from traditional in-house quality control.Text&TranslationlQuality assurance strives through documentation of performance and
28、characteristics at each stage of manufacture to ensure that the product will perform at the intended level.Whereas quality control is involved directly with manufacturing operations,quality assurance is involved with the customer support responsibilities generally found within the marketing function
29、.Many industrial organizations have chosen to establish an independent quality assurance sub-function within the manufacturing function and have placed the technical responsibilities of quality control,namely process control,within the manufacturing engineering organization.Text&Translationl1.产品的测试产
30、品的测试 l产品的测试是所有工艺控制过程中至关重要的部分。也可以认为它是整个工艺过程监控中的质量检验部分。如果质量控制计划是适当的和被准确执行的，产品的性能有保障而总体的测试是多余的。由于这个原因，产品质量的完全测试只不过是在客户接受该零件之前合同中的要求。但产品测试不单纯是指所有零件校验的总和。为支持产品的设计原理，为在设计中推行更多的改进方法和开发优于当前的产品，同时也为评估达到最好性能时的设计所需成本则需要收集数据。另外，它也是检验设计的一种方法，因为并不是所有的设计参数都被完全地计算和预算。Text&Translationl产品测试工程师的工作与设计工程师类似，就是为测试提供有用的数据
31、。他们必须与制造各个阶段的工程师协同工作。在设计中产品缺乏测试并不少见，这是制造工艺过程中需要重点修正的方面。公司制造较多的产品原型而投入市场运行的产品却较少，这显然是正确的。因此，如设计工程师一样制造工程师关心产品的测试结果。l对于复杂的产品来说，在整个工艺控制过程中产品测试逐渐成为一个重要的部分。它为公司提供了较高的可信度，使产品达到客户所希望的性能；这也是一个有价值的市场调控工具，它帮助公司在客户中树立一定的声誉。Text&Translationl2.几何误差几何误差 l几何误差定义为独立机械零件误差(如线性轴承运动的直线度)。与几何误差相关的是准静态时的表面精度，这与零件表面的相对运动
32、有关。几何误差可以被削弱和保持(系统误差)，可能滞后出现(如间隙)或者随机产生。许多因素影响几何误差，包括表面的直线度(如图14-1 所示)、表面粗糙度、轴承预载荷、相对弹性设计原则的运动学和结构设计准则。Text&Translation图14-1 表面形状引起的直线度误差和表面粗糙度误差Text&Translationl3.配合与公差配合与公差l 配合定义为两个相互结合的零件的不同关联关系。公差定义为最大极限尺寸与最小极限尺寸之间的差异。公差也等于上下偏差的代数和，如图14-2所示。Text&Translation图14-2 基本尺寸、偏差和公差示意图Text&Translationl根据孔
33、和轴的实际尺寸极限，配合分为以下几种。l(1)间隙配合，即在配合零件间产生一个间隙。这时，孔公差带完全位于轴公差带上方。l(2)过盈配合，即在配合零件间产生一个干涉。这时，孔公差带完全位于轴公差带下方。l(3)过渡配合，即依据产品实际尺寸在配合零件间产生一个间隙或干涉。l公差用一个字母(有时是两个字母)或符号和数字表示。大写表示孔，小写表示轴。字母表示了公差带相对基本尺寸零线的位置。数字表示公差值，称为公差等级或公差质量。公差的位置和等级都作用在基本尺寸上。一个带有公差的尺寸定义为基本尺寸后接字母和数字，如20H7 或 20g6。Text&Translationl在实际工程制图中，孔和轴的公差
34、被写在基本尺寸后，分别是孔在上方，轴在下方。l同样，配合通常表示为孔和轴的基本尺寸后接相应的公差等级符号。l4.质量规划质量规划 l这是工艺控制中的规划和决策行为，有时指工艺规划或监控规划。工程师提出充分的执行计划以确保产品性能到达设计要求。以实际的生产效率测量和工件测量为指导来生成可应用的计划和方法。在制造过程中，质量规划工程师指定监控和非破坏性测试的内容。他们还要根据工具设计工程师的要求指定监控的类型和指导测试，以确定产品是合格还是被淘汰。Text&Translationl正常的生产制造会在设计基础上产生一定比例的偏差。有一些很重要，还一些基本无关。估计偏差和确定适合的矫正方案是质量规划工
35、程师的责任。他们确保在整个生产效率测量和工件测量过程中的纠偏活动及影响因素，避免制造计划的重做。当质量仲裁者根据设计图评定质量偏差时，用质量规划形成的数据库来评估各个工序和主要功能的履行情况。保持稳定的功能是可能的和令人期待的。质量规划还可以向管理部门汇报质量水平的增减。Text&Translationl偏差强弱的评估统计数字报告了质量状况。这自然引出一个由偏差引起的修理工作的成本估计。修理工作是制造损失的组成部分，是系统质量水平的一个重要的测量方法。制造损失是一个有意义的测量值，是操作员和前期工作者关注的细节。高损耗表明操作管理的欠缺。质量规划工程师的责任是设定制造损失、预算和测量方针。Te
36、xt&Translationl5.质量控制质量控制 l从传统意义上讲，质量控制是制造和设计之间的联系纽带。该功能解释为制造和推行质量计划的设计规范，它是综合制造工程方法和操作过程的规划指导。质量控制还负责向管理部门建议容许的制造损耗。基于产品设计的复杂性，特定精度水平需要在容许范围内。传统的质量控制是通过设置不允许超出的预算负数来控制制造损耗，从而建立测量和纠错活动的准则。Text&Translationl在过去的一二十年里，随着市场和用户的日益增加，质量控制与建立文件系统保证产品质量水平有关。这一新的角色引领质量保证新主题，区别于传统的内部质量控制体系。l质量保证力争通过执行文件和每个制造阶
37、段的特征来确保产品按预期水平完成制造。质量控制与制造过程直接相关，而且质量保证一般还和包含在市场调控功能中的用户支持职责有关。许多工业组织在制造功能下选择建立独立的质量保证子功能，设置了质量控制技术责任，即包含在制造工程组织内的工艺过程控制。Complex Sentence Analysisl1 It allows for gathering data that support the design theory of the product,for interpretations to be made for further improvements in design so that fu
38、ture products will be better than present ones,and for evaluation of design evolution toward better performance costs.为支持产品的设计原理，为在设计中推行更多的改进方法和开发优于当前的产品，同时也为评估达到最好性能时的设计所需成本则需要收集数据。l it：形式主语，代替that从句以及两个for短语 l句中的两个for介词短语引导状语从句lallow for sth.考虑到，在这里可译为需要Complex Sentence Analysisl2 Many factors aff
39、ect geometric errors including:surface straightness(see Fig.14.1),surface roughness,bearing preload,kinematics versus elastic design principles and structural design philosophies.许多因素影响几何误差，包括表面的直线度(见图14-1)、表面粗糙度、轴承预载荷、相对弹性设计原则的运动学和结构设计准则。l surface straightness：平面度lversus elastic design principles(相
40、对于弹性设计原理)介词短语修饰 kinematics(运动学)Complex Sentence Analysisl3 Similarly,a fit is indicated by the basic size common to both the mating components,followed by the appropriate symbols corresponding to each component.同样，配合通常表示为孔和轴的基本尺寸后接相应的公差等等级符号。l is indicated by：被动语态，意思是简要的说明lcommon to both the mating
41、components 做the basic size的后置定语l followed by：过去分词短语修饰 the basic size.Key to Exercisesl.Translate the following phrases into Chinese or English.l1.产品检测l2.process controll3.几何误差l4.fit and tolerancel5.间隙配合l6.Interference fitl7.过渡配合l8.the grade or quality of tolerancel9.质量规划 l10.quality controlKey to Ex
42、ercisesl.Mark the following statement with True(T)or False(F)according to the text.l1Tl2T l3T l4F l5TKey to Exercisesl.Fill in the blanks with the suitable words or phrases given below.l1.between manufacturing and designl2.responsible for l3.based onl4.Quality controll5.Measurement and corrective ac
43、tionKey to Exercisesl.Translate the Chinese parts given in the brackets into English.l1.between the sizes of two mating partsl2.Capital letters are used for holes and small letters for shafts.l3.In engineering drawing practicel4.This is the planning and strategy activity of process controll5.setting the manufacturing losses,budgets,and measurements policylThe end!