关 键 词：

机械毕业设计论文

资源描述：

工艺夹具毕业设计54万向节滑动叉工艺设计,机械毕业设计论文

内容简介：

Common difference and surface roughness The modern technology is more and more strict to the components sizeprecision request. Moreover, at present many components have spread ineach place different factory production, therefore must makes thestrict stipulation to these components sizes and the production,guaranteed they have the interchangeability. Causes it for the components sign note size to change in a stipulationsector, guaranteed they have the interchangeable technology to becalled the common difference technology. Allows each size certainly tohave in the stipulation scope changes the momentum, is called thecommon difference. For example, a components size may express for200.5, its common difference (size changes momentum) is 1.00mm. In does not affect the components performance in the situation, mustgive the size as far as possible big common difference, by falls theproduction cost to is lowest. The production cost reduces along withthe common difference elevates. Some three expressions size common difference way: Unidirectional,bidirectional and limit way. When uses the positive and negativecommon difference, adds to the common difference is been called thebasic size the theory size to come up. When only allows the size tohave (or changes in a big way to the basic size sole direction, orchanges slightly) when change, is the unilateral tolerance. May(change in the size when the basic size two directions big or changesslightly) all may change, the common difference is bidirectional. Thecommon difference also may use the limit form to produce, theexpression components contour is biggest and most light-sized. Some and common difference related terminology and definition asfollows: Common difference: Upper limit and lower limit bad value stipulatedwhich for some size. Basic size: The theory size, is calculates the extreme dimension andthe deviation outset size. Deviation The hole size or the axis size subtracts the basic sizeobtained bad value.The components biggest extreme dimension subtracts itsbasic size obtained bad value. The components smallest extreme dimension subtracts itsbasic size obtained bad value. Actual size: After processing components actual size. ntsCoordination: Two assemble in between together components degree. May divide into the coordination three kinds: Gapcoordination, excessively full coordination, transition fit. Gap coordination: Two assemble in between the together fitting has thegap the coordination. Excessively full coordination: Two assemble in between the togethercomponents has the full coordinate - axis to be bigger than the hole,needs to make an effort the coordination which or the pressure carrieson, has is similar to two components welds in together effect. Transition fit: In two assembles in between the together components orexists excessively full, or has the gap the coordinate - axis to beallowed to be smaller than or to be bigger than the hole, but still instipulation common difference. Selective assembly: Through manually tries to match chooses and theunit method. Through this method, may assemble common differencebigger components which makes under a lower cost. It may take the highmanufacture precision and is easy between the components onecompromise method which assembles. Uses the smallest hole size to take the computation commondifference and the processing remainder basic size. When uses thestandard the drill bit, the engine bed carries on theprecision processing to the hole,the system is extremelyeffective. Uses the smallest hole the size to take the basic size isbecause the hole size may change in a big way through themachine-finishing, but cannot reduce. May defer to when the unusual high accuracy the standard sizeprovides, uses the basic shaft system is suitable. When computationcommon difference and remainder, uses the axis most large diameter totake the basic size. This is because the axis may turn a smaller sizethrough the processing, but the basic size cannot increase. International common difference (IT) rank: A series of along withbasic size change, also provides the even precision in the stipulationrank the common difference. Altogether has 18 IT rank: IT01, IT0,IT1. IT16. Common difference mark: The mark has produced the commondifference and the coordinate specification, the basic size is anumeral, behind and expresses the IT rank numeral with the expressionbasic deviation letter. They decide the tolerance zone together thesize and the position. The capital letter represents the hole thebasic deviation, the lowercase letter represents the ntsaxis the basicdeviation. Because the superficial appearance (namely fineness) canaffect the components the performance, therefore must preciselyperform to its size to stipulate, the superficial appearance is on thesuperficial difference, including roughness, waviness, processingtexture direction and flaw. Roughness: Useful causes slightest which the work piece surface brightand clean processing craft creates surface irregularity. The surfaceroughness highly uses micron and the microinch carries on the survey. Waviness: Is surpasses roughness width the boundary big gap deviation,uses inch and a millimeter survey. May regard as roughness tosuperimpose on waviness surface surface irregularity. Processing texture direction: The superficial design directionwhich by which uses the processing method produces. Flaw: Not frequently appears or the surface defect which can appear inthe very big sector talent, it including the crack, the blowhole, thetiny crack, delimits the mark and so on. The flaw influence usually isneglected in roughness levelling. The project pattern is makes the machine part the basis. Therefore, isengaged in the manufacturing industry the staff all want the correctunderstanding to apply to the entire production process patternmeaning. Must face this kind of fact in enterprise work engineer, namely anytwo machine part all cannot make the quite same not less than. He knewin the design must consider the repetition lives the small sizedifference which mid-production produces, in the pattern superscriptnote appropriate common difference, limits the size change in thepermission scope. After the processing components outline must belocated the common difference stipulation in the region. Uses thesuitable common difference to be allowed to guarantee the product thefunction and the service life aspect all can achieve the anticipatedgoal. Each design personnel extremely are all clear, if the components allprocess the manufacture by a smaller common difference, then theproduct cost can rapidly increase. Therefore, engineers unceasinglyobtain the advice, must use as far as possible the big commondifference. However, sometimes possibly appears between each kind ofcommon difference reciprocity which needs to the function request notto conduct the full research the situation. In this kind of situation,in order to guarantee components when assembly does not give rise to aquestion or problem, not not ntsappropriately designs the personnelusually to stipulate the common difference too strictly. Is oppositeearnestly to, is thorough carries on to the common difference analyzessaid that, this obviously is a price expensive substitution way. If the product is produced by a lower price and the satisfiedmurderous intention request, stipulated the suitable processing commondifference is the most important work. The common difference size isby designs, it which the personnel determined is decided by many withthe design related condition as well as in the past when the designsimilar product obtains experience (if has this aspect experience). Ifstipulated the common difference too is small, when uses present theprocessing equipment processing work piece cannot achieve the designrequest, needs to design carries on the change. In the project pattern the place can cause many ischaotic and the economic loss. When drafts the common difference,designs the personnel to have fully to realize, must completelyachieve its design goal, in the pattern must contain the informationwhich needs. Thus, in the pattern must produce the completeinformation, and as far as possible simple was bright. In pattern eachpart all should be able to understand by everybody. In the patternexpressed the meaning regarding all uses it the personnel (design,purchase, cutting tool design, production, examination, assembly andservice department) said all should be only. The common difference may select the different sign note method in thepattern. In the unidirectional system, a limit deviation is zero,another limit deviation is the size permission completely changes themomentum. In the bidirectional system in the size sign note, uses theintermediate size and changes the momentum in its positive andnegative two directions to express. When when all sizes all occupy the material which the permissioncomponents includes for most limiting condition, called thiscomponents are at the biggest entity condition (MMC). Regarding anaxis or external dimensions, its basic size for the biggest extremedimension, it changes when the tolerance zone, only can causeminification. Regarding a hole or the internal size, its basic sizefor the smallest extreme dimension, in the tolerance zone change, onlycan cause the size to increase. Each design personnel extremely are all clear, if the components allprocess the manufacture by a smaller common difference, then theproduct cost can rapidly ntsincrease. Therefore, engineers unceasinglyobtain the advice, must use as far as possible the big commondifference. However, sometimes possibly appears between each kind ofcommon difference reciprocity which needs to the function request notto conduct the full research the situation. In this kind of situation,in order to guarantee components when assembly does not give rise to aquestion or problem, not not appropriately designs the personnelusually to stipulate the common difference too strictly. Is oppositeearnestly to, is thorough carries on to the common difference analyzessaid that, this obviously is a price expensive substitution way. If the product is produced by a lower price and the satisfiedmurderous intention request, stipulated the suitable ding-dong allsizes all occupy the material which the permission components includesto estimate when for smallest limiting condition, called thiscomponents are at the smallest entity condition (LMC). When accordingto LMC sign note common difference, regarding the external dimensions,its basic size is the smallest extreme dimension; Regarding in holesize, its basic size is the biggest extreme dimension. In thetolerance zone size change, can cause the material which thecomponents contains to estimate the increase. To producesadvantageously according to the biggest physical dimension sign notecommon difference. Regarding external dimensions, the worker or thebiggest extreme dimension carries on the processing according to itsbasic size, if it removes measures excessively slightly, but also maythrough reprocess, causes the work piece size in the permission scope.A worker when carries on the processing according to the intermediatesize, the processing deviation only can in the small scope change. Howno matter, on narrated the concept for to provide the convenientexpression form by the different way in the components patternsuperscript note common difference. In the machine manufacture, obviously as far as possible maintains thestable working condition, after but processes the size which obtainsno matter what however inevitably appears the error. In the quite samenot less than manufacture process, according to some as soon asassigns the size to process one batch of components, after theprocessing the obtained size actually and the quite same not lessthan. Has this kind of phenomenon reason to be worth the peoplestudying. Generally will produce this kind of phenomenon reason minutetwo ntsbig kind: System reason and stochastic reason. System reason: In the production process certain factors small changesmay cause the size change. The raw material performance small changemay cause the size change. The cutting tool receives the attrition andto need reto install. The speed, the lubricant, the cuttingtemperature, the operator and all that conditions can change. Throughthe system analysis research, generally may discover these reasons andmay adopt the corresponding step to eliminate it. nts公差与表面粗糙度 现代技术对零件尺寸精度的要求越来越严格。而且，目前许多零件是有散布在各地的不同厂家生产的，因此必须对这些零件的尺寸和生产做出 严格的规定，以保证它们具有互换性。 给零件标注尺寸使其在一个规定的区间内变动，以保证它们具有互换性的技术称为公差技术。允许每个尺寸在规定范围内具有一定的变动量，称为公差。例如，一个零件的尺寸可以被表示为 200.5 ，其公差（尺寸变动量）为 1.00mm。 在不影响零件性能的情况下，应当给尺寸尽可能大的公差，以把生产成本降至最低。制造成本随着公差的降低而升高。有三种表示尺寸公差的方式：单向，双向和极限方式。当采用正负公差时，就将公差加到被称为基本尺寸的理论尺寸上去。当只允许尺寸有向基本尺寸的单一方向（或者变大， 或者变小）的变动时，就是单向公差。在尺寸可以在 基本尺寸的两个方向（变大或者变小）都可以变动时，公差就是双向的。公差也可以用极限形式给出，表示零件外形的最大和最小尺寸。 一些与公差有关的术语和定义如下：公差：为某个尺寸所规定的上限与下限的差值。基本尺寸：理论尺寸，是计算极限尺寸和偏差的起始尺寸。偏差：孔的尺寸或者轴的尺寸减去基本尺寸所得的差值。上偏差：零件的最大极限尺寸减去其基本尺寸所得的差值。下偏差：零件最小极限尺寸减去其基本尺寸所得的差值。实际尺寸：加工后零件的实测尺寸。配合：两个装配在一起的零件之间的 松紧程度。可以把配合分为三类：间隙配合，过盈配合，过渡配合。间隙配合：两个装配在一起的配件之间有间隙的配合。过盈配合：两个装配在一起的零件之间有过盈的配合 轴大于孔，需要用力或者压力进行的配合，具有类似于将两个零件焊接在一起的效果。过渡配合：在两个装配在一起的零件之间或者存在着过盈，或者存在着间隙的配合 轴可以小于或者大于孔，但仍在规定的公差内。选择装配：通过手工试配来选择并装配零件的方法。通过这种方法，可以装配在较低的成本下制造出来的公差较大的零件。它可以作为高的制造精度和易于装配的零件之间的一种折中的方 法。基孔制：采用最小的孔尺寸作为计算公差和加工余量基本尺寸。当采用标准的钻头、铰刀和机床对孔进行精度加工时，基孔制系统是非常有nts效的。采用最小的孔的尺寸作为基本尺寸是因为孔的尺寸可以通过机械加工变大，但不能减小。当轴可以按照非常的高精度的标准尺寸提供时，采用基轴制是适用的。计算公差和余量时，采用轴的最大直径作为基本尺寸。这是因为轴可以通过加工变成较小的尺寸，但基本尺寸不能增加。国际公差（ IT）等级：一系列随基本尺寸变化，且在规定等级内提供均匀精度的公差。共有 18个 IT等级： IT01，IT0， IT1， ,IT 16.公差符号：符号给出了公差和配合的技术要求，基本尺寸是一个数字，后面跟着表示基本偏差的字母和表示 IT 等级的数字。它们共同决定公差带的大小和位置。大写字母代表孔的基本偏差，小写字母代表轴的基本偏差。由于表面形貌（即表面光洁度）会影响零件的性能，因此对其大小必须精确地加以规定，表面形貌是表面上的差异，包括粗糙度、波度、加工纹理方向和缺陷。粗糙度：有用来使工件表面光洁的加工工艺所造成的最细微的表面不平度。表面粗糙度的高度采用微米和微英寸进行测量。波度：是超过粗糙度宽度的界限的大间隔偏差，采用英寸和毫米测量。可 将粗糙度看作叠加在波度表面上的表面不平度。加工纹理方向：由所采用的加工方法所产生的表面刀痕图案的方向。缺陷：不经常出现或