【正文】 。當(dāng)主計(jì)算機(jī)出現(xiàn)故障時(shí)，由其控制的所有機(jī)床都將停止工作。這個(gè)問(wèn)題促使了計(jì)算機(jī)數(shù)字控制技術(shù)的產(chǎn)生。 微處理器的發(fā)展為可編程邏輯控制器和微型計(jì)算機(jī)的發(fā)展做好了準(zhǔn)備。這兩種技術(shù)為計(jì)算機(jī)數(shù)控（ CNC）的發(fā)打下了基礎(chǔ)。采用 CNC 技術(shù)后，每臺(tái)機(jī)床上都有一個(gè)可編程邏輯控制器或者微機(jī)對(duì)其進(jìn)行數(shù)字控制。這可以使得程序被輸入和存儲(chǔ)在每臺(tái)機(jī)床內(nèi)部。它還可以在機(jī)床以外編制程序，并將其下載到 每臺(tái)機(jī)床中。計(jì)算機(jī)數(shù)控解決了主計(jì)算機(jī)發(fā)生故障所帶來(lái)的問(wèn)題，但是它產(chǎn)生了另一個(gè)被稱(chēng)為數(shù)據(jù)管理的問(wèn)題。同一個(gè)程序可能要分別裝入十個(gè)相互之間沒(méi)有通訊聯(lián)系的微機(jī)中。這個(gè)問(wèn)題目前正在解決之中，它是通過(guò)采用局部區(qū)域網(wǎng)絡(luò)將各個(gè)微機(jī)聯(lián)接起來(lái)，以得于更好地進(jìn)行數(shù)據(jù)管理。 普通車(chē)床作為最早的金屬切削機(jī)床的一種，目前仍然有許多有用的和為人要的特性和為人們所需的特性。現(xiàn)在，這些機(jī)床主要用在規(guī)模較小的工廠(chǎng)中，進(jìn)行小批量的生產(chǎn)，而不是進(jìn)行大批量的和產(chǎn)。 在現(xiàn)代的生產(chǎn)車(chē)間中，普通車(chē)床已經(jīng)被種類(lèi)繁多的自動(dòng)車(chē)床所取代，諸如自動(dòng)仿形車(chē)床，六角車(chē)床和自動(dòng)螺絲車(chē)床?，F(xiàn)在，設(shè)計(jì)人員已經(jīng)熟知先利用單刃刀具去除大量的金屬余量，然后利用成型刀具獲得表面光潔度和精度這種加工方法的優(yōu)點(diǎn)。這種加工方法的生產(chǎn)速度與現(xiàn)在工廠(chǎng)中使用的最快的加工設(shè)備的速度相等。 普通車(chē)床的加偏差主要信賴(lài)于操作者的技術(shù)熟練程度。設(shè)計(jì)工程師應(yīng)該認(rèn)真地確定由熟練工人在普通車(chē)床上加工的試驗(yàn)件的公差。在把試驗(yàn)伯重新設(shè)計(jì)為生產(chǎn)零 件時(shí)，應(yīng)該選用經(jīng)濟(jì)的公差。 六角車(chē)床 對(duì)生產(chǎn)加工設(shè)備來(lái)說(shuō)，目前比過(guò)去更注重評(píng)價(jià)其是否具有精確的和快速的重復(fù)加工能力。應(yīng)用這個(gè)標(biāo)準(zhǔn)來(lái)評(píng)價(jià)具體的加工方法，六角車(chē)床 可以獲得較高的質(zhì)量評(píng)定。 在為小批量的零件（ 100~200 件）設(shè)計(jì)加工方法時(shí)，采用六角車(chē)床是最經(jīng)濟(jì)的。為了在六角車(chē)床上獲得盡可能小的公差值，設(shè)計(jì)人員應(yīng)該盡量將加工工序的數(shù)目減至最少。 自動(dòng)螺絲車(chē)床 自動(dòng)螺絲車(chē)床通被分為以下幾種類(lèi)型：?jiǎn)屋S自動(dòng)、多軸自動(dòng)和自動(dòng)夾緊車(chē)床。自動(dòng)螺絲車(chē)床最初是被用來(lái)對(duì)螺釘和類(lèi)似的帶有螺紋的零件進(jìn)行自動(dòng)化和快速加工的。但是，這種車(chē)床的用途早就超過(guò)了這個(gè)狹窄的范圍?，F(xiàn)在，它在許多種類(lèi)的精密零件的大批量生產(chǎn)中起著重要的作用。工件的數(shù)量對(duì)采用自動(dòng)螺絲車(chē)床所加工的零件的經(jīng)濟(jì)性有較大的影響 。如果工件的數(shù)量少于 1000 件，在六角車(chē)床上進(jìn)行加工比在自動(dòng)螺絲車(chē)床上加工要經(jīng)濟(jì)得多。如果計(jì)算出最小經(jīng)濟(jì)批量，并且針對(duì)工件批量正確地選擇機(jī)床，就會(huì)降低零件的加工成本。 自動(dòng)仿形車(chē)床 因?yàn)榱慵谋砻娲植诙仍诤艽蟪潭壬先Q于工件材料、刀具、進(jìn)給量和切削速度，采用自動(dòng)仿形車(chē)床加工所得到的最小公差一定是最經(jīng)濟(jì)的公差。 在某些情況下，在連續(xù)生產(chǎn)過(guò)程中，只進(jìn)行一次切削加工時(shí)的公差可以達(dá)到 。對(duì)于某些零件，槽寬的公差可以達(dá)到 。鏜孔和休用單刃刀具進(jìn)行精加工時(shí)，公差可達(dá)到 。在希望 獲得最大主量的大批量生產(chǎn)中，進(jìn)行直徑和長(zhǎng)度的車(chē)削時(shí)的最小公差值為 是經(jīng)濟(jì)的。 附件 2：外文原文（復(fù)印件） Lathes Lathes are machine tools designed primarily to do turning, facing and boring, Very little turning is done on other types of machine tools, and none can do it with equal facility. Because lathes also can do drilling and reaming, their versatility permits several operations to be done with a single setup of the work piece. Consequently, more lathes of various types are used in manufacturing than any other machine tool. The essential ponents of a lathe are the bed, headstock assembly, tailstock assembly, and the leads crew and feed rod. The bed is the backbone of a lathe. It usually is made of well normalized or aged gray or nodular cast iron and provides s heavy, rigid frame on which all the other basic ponents are mounted. Two sets of parallel, longitudinal ways, inner and outer, are contained on the bed, usually on the upper side. Some makers use an inverted Vshape for all four ways, whereas others utilize one inverted V and one flat way in one or both sets, They are precisionmachined to assure accuracy of alignment. On most modern lathes the way are surfacehardened to resist wear and abrasion, but precaution should be taken in operating a lathe to assure that the ways are not damaged. Any inaccuracy in them usually means that the accuracy of the entire lathe is destroyed. The headstock is mounted in a foxed position on the inner ways, usually at the left end of the bed. It provides a powered means of rotating the word at various speeds . Essentially, it consists of a hollow spindle, mounted in accurate bearings, and a set of transmission gearssimilar to a truck transmission—through which the spindle can be rotated at a number of speeds. Most lathes provide from 8 to 18 speeds, usually in a geometric ratio, and on modern lathes all the speeds can be obtained merely by moving from two to four levers. An increasing trend is to provide a continuously variable speed range through electrical or mechanical drives. Because the accuracy of a lathe is greatly dependent on the spindle, it is of heavy construction and mounted in heavy bearings, usually preloaded tapered roller or ball types. The spindle has a hole extending through its length, through which long bar stock can be fed. The size of maximum size of bar stock that can be m