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设计名称
  尺寸控制
设计编号
  A8-176
设计软件
  Word
包含内容
  WORD文档
说明书页数
  8页(中英文)
图纸数量
  机械翻译(无图)
推荐指数
  较好
价格:
  优惠中
整理日期
  2012,07,19
整理人
  小木
购买流程
  <点此查看如何购买本站设计>
设计简介

附录
附录1
英文翻译
Dimensional Control
In the early days of engineer, the mating of parts was achieved by machining one part as nearly as possible to the required size, machining the mating part nearly to size, and then completing its machining, continually offering the other part to it, until thedesired relationship was obtained. If it was inconvenient to offer one part to the other part during machining, the final work was done at the bench by a fitter, who scraped the mating parts until the desired fit was obtained, the fitter therefore being a ‘fitter’ in the literal sense. It is obvious that the two parts would have to be done all over again. In these days, we expect to be able to purchase a replacement for a broken part, and for it to function correctly without the need for scraping and other fitting operations. When one part can be used ‘off the shelf’ to replace another of the same dimension and material specification, the parts are said to be to be interchangeable. A system of interchangeability usually lowers the production costs, as there is no need for an expensive ‘fiddling’ operation, and it also benefits the customer in the event of the need to replace worn parts. It also, however, demands that the dimension of mating parts be specified, and that dimensional variations, due to machine and operator shortcomings, be taken into account. Some form of inspection must be introduced to ensure that the manufacture is controlled; this is particularly important, because dimensional errors may not be revealed until some time has elapsed, and often many miles from the place where the machining was done.
1. Tolerance and Limits of size
Since it is accepted that it is virtually impossible to manufacture a part without error, or in the rare event of a part being without error, to be able to proclaim it to be perfect (because the measuring instruments are subject to errors), it is necessary to indicate the maximum errors permitted. The draughtsman must indicate the largest and smallest sizes that the limits of size, and the difference between them is called the tolerance, the actual tolerance must be increased with size. The tolerance should be as large as possible, to keep the cost to a minimum.The method of indicating, on a drawing, the permitted tolerance depends mainly upon the type of operation involved, but local preference must also be taken into account. The following examples will illustrate some of the methods used,
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附录2
中文译文
尺寸控制
在早期的工程(问题)中,配合零件获得的方法是,首先尽可能把一个零件加工到所
需的尺寸,再将与它相配合的零件加工到接近所需尺寸,不断将这两个零件试配,再进一
步加工直至获得所许的配合关系。如果加工中不便于将两个零件进行试配,则最后的工作
是由钳工在钳工台完成,钳工刮削配合零件直至达到所许配合,因此“钳工”在英文中用‘fitter’(适当的,适配的)这一词。显然,两个配合件应该总是在一起(工作)当其中任意一个需要替换时,所有的适配刮削工作又要从头开始。这时,我们期盼能购买到可以替换坏掉零件的替用品,而无须刮削或其它钳工操作就能正常工作。
当一个零件一从架子上拿来就可以替换同样尺寸同样材料规格的另一个零件,就说这
个零件是可互换的。具有可互换性的系统不必进行高成本的辅助刮削工作,因此降低了产
品的成本。在要替换掉磨损的零件时,零件的可互换性对维护而言也是大有好处的。然而,
可互换系统要求配合件的 尺寸必须规格化,还必须考虑由于加工操作的不足之处引入的尺寸变化。必须采用某种形式的检测方法以确保对加工的控制。这一点非常重要。因为尺寸误差有时可能要过一段时间才会发现,而此时却已远离加工的地方。
1. 公差与极限尺寸
大家知道,事实上零件不可能毫无误差的加工出来,或者说没有误差的零件是不可能
的,要说明尺寸的好坏(因为测量仪器必然有误差),就有必要指出最大允许误差。绘图
人员必须标明零件正常工作时的最大允许尺寸和最小允许尺寸。这些尺寸的极限值就称作
极限尺寸,它们之间的差值称为公差。公差的大小取决于所涉及的加工操作类型、机械工
的技能、机床的精确度以及零件的尺寸。对于给定级别的公差,实际公差应随着尺寸的增
大而增大。公差应尽可能取大以使加工成本最小。
在图上标注公差时,许用公差主要取决于所用操作类型,但也必须考虑本国的优先级。
以下用例子说明用到的一些标注方法:
(1) 单边极限。单边极限通常用于当两个面之间的距离,或孔径、轴径被指定的情况下。例如,当直径要圆整时,机械工更愿意向最大允许尺寸圆整,这样,当他加工到所得直径尺寸略大于最大允许尺寸时,还可以在整个公差范围内再切一次而不产生废品。制图员可能将公称直径是75-0.012mm 的轴标注为D75mm。同样的,公称直径是75mm 的孔也可能标的尺寸是D75-0.012mm,这同样也适用于轴的标注。
(2) 双边极限。双边极限通常用于:比如当孔的位置已确定的情况下。机床操作人员可能将孔的位置定得较接近或远离所需数据,而且,当孔的加工已经开始,操作人员不可能改变孔的位置,他必须在尺寸位置限度间加工,以便在最大误差时不会使零件变成废品。因此,应将两个孔的中心距规定出来,比如,为100+0.02mm。
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此为机械毕业设计之翻译

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