外文翻譯--機(jī)械加工基礎(chǔ)簡(jiǎn)介

1、<p><b>　　中文2692字</b></p><p><b>　　附 錄</b></p><p>　　Introduction to basic machining</p><p>　　Mechanism of Surface Finish Production </p><p>　

2、　There are basically five mechanisms which contribute to the production of a surface which have been machined. There are: </p><p>　　(1) The basic geometry of the cutting process. In, for example, single poin

3、t turning the tool will advance a constant distance axially per revolution of the work piece and the resultant surface will have on it, when viewed perpendicularly to the direction of tool feed motion, a series of cusps

4、which will have a basic form which replicates the shape of the tool in cut. </p><p>　　(2) The efficiency of the cutting operation. It has already been mentioned that cutting with unstable built-up-edges will

5、 produce a surface which contains hard built-up-edge fragments which will result in a degradation of the surface finish. It can also be demonstrated that cutting under adverse conditions such as apply when using large fe

6、eds small rake angles and low cutting speeds, besides producing conditions whichcontinuous shear occurring in the shear zone, tearing takes place, discontinuou</p><p>　　(3) The stability of the machine tool.

7、 Under some combinations of cutting conditions: work piece size , method of clamping, and cutting tool rigidity relative to the machine tool structure, instability can be set up in the tool which causes it to vibrate. Un

8、der some conditions the vibration will built up and unless cutting is stopped considerable damage to both the cutting tool and work piece may occur. This phenomenon is known as chatter and in axial turning is characteriz

9、ed by long pitch helic</p><p>　　(4) The effectiveness of removing sward. In discontinuous chip production machining, such as milling or turning of brittle materials, it is expected that the chip (sward) will

10、 leave the cutting zone either under gravity or with the assistance of a jet of cutting fluid and that they will not influence the cut surface in any way. However, when continuous chip production is evident, unless steps

11、 ate taken to control the swarf it is likely that it will impinge on the cut surface and mark it. Inevita</p><p>　　(5) The effective clearance angle on the cutting tool. For certain geometries of minor cutti

12、ng edge relief and clearance angles it is possible to cut on the major cutting edge and burnish on the minor cutting edge. This can produce a good surface finish but, of course, it is strictly a combination of metal cutt

13、ing and metal forming and is not to be recommended as a practical cutting method. However, due to cutting tool wear, these conditions occasionally arise and lead to a marked change in the </p><p>　　Surface F

14、inishing and Dimensional Control</p><p>　　Products that have been completed to their proper shape and size frequently require some type of surface finishing to enable than to satisfactorily fulfill their fun

15、ction. In some cases, tit is necessary to improve the physical properties of the surface material for resistance to penetration or abrasion. In many manufacturing processes, the product surface is left with dirt, chips,

16、grease, or other harmful material upon it. Assemblies that are made of different materials, or from the same materi</p><p>　　Surface finishing many sometimes become an intermediate step processing. For insta

17、nce, cleaning and polishing are usually essential before any kind of plating process. Some of the cleaning procedures are also used for improving surface smoothness on mating parts and for removing burrs and sharp corner

18、s, which might be harmful in later use. Another important need for surface finishing is for corrosion protection in a variety of environments. The type of protection procedure will depend largely up</p><p>　

19、　Satisfying the above objectives necessitates the use of main surface-finishing methods that involve chemical change of the surface mechanical work affecting surface properties, cleaning by a variety of methods, and the

20、application of protective coatings, organic and metallic. </p><p>　　In the early days of engineering, the mating of parts was achieved by machining one part as nearly as possible to the required size, machin

21、ing the mating part nearly to size, and then completing its machining, continually offering the other part to it, until the desired relationship was obtained. If it was inconvenient to offer one par to the other part dur

22、ing 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 </p><p>　　When one part can be used ‘off the shelf’ to replace ano

23、ther of the same dimension and material specification, the parts are said to be interchangeable. A system of interchangeability usually lowers the production costs as there is no need for an expensive, ‘fiddling’ operati

24、on, and it benefits the customer in the event of the need to replace worn parts. </p><p>　　Limits and Tolerances</p><p>　　Machine parts are manufactured so they are interchangeable. In other wor

25、ds, each part of a machine or mechanism is made to a certain size and shape so it will fit into any other machine or mechanism of the same type. To make the part interchangeable, each individual part must be made to a si

26、ze that will fit the mating part in the correct way. It is not only impossible, but also impractical to make many parts to an exact size. This is because machines are not perfect, and the tools become worn. A</p>

27、<p>　　A tolerance is the total permissible variation in the size of a part.</p><p>　　The basic size is that size from which limits of size are derived by the application of allowances and tolerances.<

28、;/p><p>　　Sometimes the limit is allowed in only one direction. This is known as unilateral tolerance.</p><p>　　Unilateral tolerancing is a system of dimensioning where the tolerance (that is varia

29、tion) is shown I only one direction from the nominal size. Unilateral tolerancing allow the changing of tolerance on a hole or shaft without seriously affecting the fit. </p><p>　　When the tolerance is in b

30、oth directions from the basic size, it is known as a bilateral tolerance (plus and minus). </p><p>　　Bilateral tolerancing is a system of dimensioning where the tolerance (that is variation) is split and is

31、shown on either side of the nominal size. Limit dimensioning is a system of dimensioning where only the maximum and minimum dimensions are shown. Thus, the tolerance is the difference between these two dimensions.</p&

32、gt;<p>　　Introduction of Machining of:</p><p>　　Machining as a shape-producing method is the most universally used and the most important of all manufacturing processes. Machining is a shape-producing

33、 process in which a power-driven device causes material to be removed in chip form. Most machining is done with equipment that supports both the work piece and cutting tool although in some cases portable equipment is us

34、ed with unsupported work piece.</p><p>　　Low setup cost for small quantities. Machining has two applications in manufacturing. For casting, forging, and pressworking, each specific shape to be produced, even

35、 one part, nearly always has a high tooling cost. The shapes that may be produced by welding depend to a large degree on the shapes of raw material that are available. By making use of generally high cost equipment but w

36、ithout special tooling, it is possible, by machining, to start with nearly any form of raw material, so long as th</p><p>　　Close accuracies, good finishes. The second application for machining is based on t

37、he high accuracies and surface finishes possible. Many of the parts machined in low quantities would be produced with lower but acceptable tolerances if produced I high quantities by some other process. On the other hand

38、, many parts are given their general shapes by some high quantity deformation process and machined only on selected surfaces where high accuracies are needed. Internal threads, for example, are sel</p><p>&l

39、t;b>　　外文文獻(xiàn)翻譯</b></p><p><b>　　機(jī)械加工基礎(chǔ)簡(jiǎn)介</b></p><p><b>　　表面粗糙度的技術(shù)</b></p><p>　　在已經(jīng)進(jìn)行機(jī)械加工過(guò)的表面，有五種基本的影響其表面粗糙度的技術(shù)。</p><p>　　1、切斷過(guò)程的基本幾何學(xué). 例如，

40、在單點(diǎn)車(chē)削時(shí)，工件每轉(zhuǎn)一周，刀具就沿軸線方向進(jìn)給一個(gè)固定的距離。從垂直刀具進(jìn)給的方向觀察，所得到的表面上有很多尖角，這些尖角的形狀與切削刀具的形狀相同。</p><p>　　2、切斷操作的效率. 已經(jīng)提過(guò)的用不穩(wěn)定的切削瘤切削將會(huì)加工出包含有堅(jiān)硬的切削瘤碎片在上面的表面，而這些將會(huì)導(dǎo)致表明粗糙度的等級(jí)降低。已經(jīng)證明，在采用進(jìn)給量大，前角小，切削速度低的不利情況下，除了產(chǎn)生不穩(wěn)定的切削瘤外，切削過(guò)程也會(huì)不穩(wěn)定。同時(shí)

41、，在切削區(qū)里進(jìn)行的也不再是切削，而是撕裂，導(dǎo)致厚度不均勻，不連續(xù)的切削，加工出的表面質(zhì)量差。在切削加工延展性良好的金屬材料，如銅和鋁時(shí)，這種情況就尤為突出。</p><p>　　3、機(jī)械工具的穩(wěn)定性。在許多聯(lián)合切削的情況下：工件的大小，夾緊的方法，和切斷工具相對(duì)于機(jī)床結(jié)構(gòu)的堅(jiān)硬度，不穩(wěn)定性是建立在使其變化的工具上的。在某些情況下，這種變化將達(dá)到并保持很長(zhǎng)一段時(shí)間，在另外一些情況下，這種變化將會(huì)產(chǎn)生，除非切斷停止，

42、否則，將肯定會(huì)同時(shí)對(duì)切斷刀具和工具產(chǎn)生破壞。這種現(xiàn)象就是知名的刀振，在軸向轉(zhuǎn)動(dòng)被描述為在工件表面的長(zhǎng)間距螺旋狀帶和段間距波動(dòng)在機(jī)械加工的過(guò)渡表面。</p><p>　　4、刀刃的移動(dòng)效率。在不連續(xù)的產(chǎn)品加工過(guò)程中例如易碎材料的磨或旋轉(zhuǎn)，我們期望碎片在重力作用或在冷卻液的噴射作用下將離開(kāi)切削面域。而且怎么也不會(huì)影響切削表面。然而，在連續(xù)切削時(shí)，產(chǎn)品是明顯的，除非逐步控制刀刃，否則他很有可能中級(jí)切削表面并在其上留下記

43、號(hào)。不可避免，這記號(hào)在旁邊樣子不美的, 時(shí)常導(dǎo)致差的表面粗糙度。</p><p>　　5、切斷工具的有效清除角。由于副切削刃的某種幾何特征減輕和清除了角，使得在主切削面上主切削刃切削和副切削刃打磨變得可能。這樣能加工出良好的表面粗糙度，但是，當(dāng)然，它嚴(yán)格來(lái)講，是一種金屬切削和金屬成型的綜合，而不失被認(rèn)為的一種實(shí)際的切削方法。然而，歸功于切削工具的表面處理，這些情況偶爾才會(huì)出現(xiàn)，并導(dǎo)致了表面特性的標(biāo)志性改變。<

44、;/p><p>　　表面精整加工與尺寸控制</p><p>　　產(chǎn)品在被加工成它們的適當(dāng)?shù)耐庑魏痛笮r(shí)，經(jīng)常地需要各種的表面精整加工，使得其能夠比較令人滿意地履行它們的功能. 在一些情況下，通過(guò)提高材料表面的物理特性來(lái)抵抗腐蝕和磨損是非常重要的。在許多制造過(guò)程中，產(chǎn)品表面上都?xì)埩粲形酃?，碎屑，油漬以及其它有害的材料。假設(shè)那是由不同種金屬材料，或是由同一種金屬材料在不同的加工方式中所造成的，大多

45、數(shù)需要一些特殊的表面處理技術(shù)來(lái)提供均勻的外表面。</p><p>　　有時(shí)表面精整加工也許只是中間階段處理，例如，清潔的和磨光在任何一種電鍍之前都是必不可少的工序。有些清潔程序是為了改善配合處表面的光滑程度，或是清除會(huì)對(duì)稍候工序產(chǎn)生有害作用的毛刺和尖角。表面精整加工的另一重要需要就是為了在各種各樣的環(huán)境下防腐蝕。這種保護(hù)程序很大程度上依賴(lài)于預(yù)期的暴露，考慮到材料將被保護(hù)和其所包含的經(jīng)濟(jì)因素。</p>

46、<p>　　滿意于上表面材料使應(yīng)用主要表面精整技術(shù)成為必然性，而這技術(shù)包括材料工作表面特性在化學(xué)上的改變，用各種方法清洗，以及有機(jī)的和金屬的保護(hù)膜的應(yīng)用。 </p><p>　　在早期的工程中，零部件的裝配是這樣完成的：加工一個(gè)部件使其盡可能的達(dá)到要求的大小，加工裝配部件接近大小時(shí)，也就完成了它的加工，繼續(xù)提供另一部件，直到獲得所要求的配合關(guān)系。如果在加工一個(gè)部件時(shí)不方便提供另一部件，那么最后的工作將

47、交予裝配工完成，它刮削裝配部件直到獲得要求的配合。因此，裝配工也就成為了“fitter”在字面上的意思了。很顯然，這兩部件將必然保持在一起，最重要的是其中一個(gè)具有互換性，裝配也將全部重新完成。在這期間，我們希望能更換一個(gè)已經(jīng)壞掉了的零件，并且在不需要刮磨和其它裝配作業(yè)的情況下就能具有原有功能。</p><p>　　如果一個(gè)部件能被用作為備用件去替換另一格同樣尺寸和材料特性的零件，那么我們就說(shuō)它具有互換性。具有互換

48、性的系統(tǒng)經(jīng)?？梢詼p少其產(chǎn)品成本，因此，對(duì)于一種昂貴的，瑣細(xì)的加工工藝沒(méi)有必要存在。而且萬(wàn)一假使顧客有必要更換磨損了的零部件。</p><p>　　大批量生產(chǎn)的零部件都具有可互換性。也就是說(shuō)，一部機(jī)器或一個(gè)系統(tǒng)的每一個(gè)零部件都做成確定的大小和規(guī)格，因此它們將用于裝入于同類(lèi)型的其它機(jī)器或系統(tǒng)。為了使零部件具有互換性，每個(gè)單個(gè)零件都必須做成可以與其配件能正確裝配。把每個(gè)零件做成確切的大小，那不但沒(méi)有必要，也是不切實(shí)際的

49、。這是因?yàn)闄C(jī)器不時(shí)完美無(wú)缺的，加工工具也會(huì)在加工過(guò)程中逐漸損耗。在允許范圍內(nèi)稍微的尺寸變動(dòng)經(jīng)常是允許的。而這個(gè)變動(dòng)的范圍是由要進(jìn)行制造的零件所決定的。例如，一個(gè)零件要做成6英寸大小，長(zhǎng)度變化范圍是正負(fù)0.003英寸。因此，這個(gè)零件制成5.997英寸或者6.003英寸都符合正確的尺寸要求。這就是極限。上限尺寸與下限尺寸之間的大小就是公差。公差就是零件大小尺寸總的允許變動(dòng)量。</p><p>　　基本尺寸就是那樣的尺

50、寸，從基本尺寸出發(fā)，應(yīng)用極限和公差來(lái)得到(推導(dǎo)出)尺寸極限。</p><p>　　有時(shí)候極限允許值存在于一個(gè)方向，這就是所謂的單邊公差。</p><p>　　單邊公差標(biāo)注是一種只表現(xiàn)在標(biāo)稱(chēng)大小的單方向的尺寸標(biāo)注制度，它允許在沒(méi)有嚴(yán)重影響配合的前提下來(lái)改變孔或軸的公差。</p><p>　　當(dāng)公差是基本尺寸向兩側(cè)延伸時(shí)，這時(shí)就變成了雙向公差（正或負(fù)）。 </p&

51、gt;<p>　　雙向公差標(biāo)注是一種當(dāng)公差在分離或者表現(xiàn)與標(biāo)稱(chēng)尺寸兩側(cè)時(shí)的尺寸標(biāo)注制度。極限尺寸標(biāo)注就是一種在僅僅表現(xiàn)出尺寸的最大值或最小值是的尺寸標(biāo)注制度。因此，公差就是在這兩種尺寸之間的距離。</p><p><b>　　機(jī)器加工的介紹</b></p><p>　　作為一種成型方法，機(jī)械加工得到了普遍應(yīng)用并且成為了機(jī)械制造過(guò)程中最重要的部分。機(jī)械加工

52、是一種在動(dòng)力驅(qū)動(dòng)下使材料以碎屑的方式分離的成型方法。盡管在某些場(chǎng)合，工件無(wú)支撐情況下，使用移動(dòng)式裝備來(lái)實(shí)現(xiàn)加工，但大多數(shù)的機(jī)械加工還是通過(guò)既支承工件又支承刀具的裝備來(lái)完成。</p><p>　　小批量的安裝成本。機(jī)械加工在機(jī)械制造中有兩種應(yīng)用形式。為鑄造，鍛造和壓力加工等的特種成型制造，僅僅只是一個(gè)零部件，幾乎經(jīng)常達(dá)到了刀具的高花費(fèi)。這些外形可能是焊接而成的，它很大程度上取決于可利用的原材料的外形。一般來(lái)說(shuō)，通過(guò)

53、利用高價(jià)設(shè)備而又無(wú)需特種加工條件下，幾乎可以從任何種類(lèi)原材料開(kāi)始，借助機(jī)械加工把原材料加工成任意所要求的結(jié)構(gòu)現(xiàn)狀，只要外部尺寸足夠大，那都是可能的。 </p><p>　　嚴(yán)密的精度，合適的表面粗糙度。機(jī)械加工的另一個(gè)應(yīng)用就是基于高精度和表面精整處理上的。對(duì)于雖低但可以接受的公差，許多小批量加工的零件可以利用其它的方法來(lái)大批量的生產(chǎn)。另一方面，許多零部件的外形是由在所選的需要高精度的表面經(jīng)過(guò)大量的機(jī)械加工所形成的