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附件1：外文資料翻譯譯文
數(shù)字控制和車(chē)削加工
1、車(chē)床
車(chē)床是一種主要被用來(lái)車(chē)削，車(chē)端面，鉆孔等工作而設(shè)計(jì)的機(jī)床，車(chē)削很少在其他類型的車(chē)床上工作，在其他種類的機(jī)床上進(jìn)行車(chē)削都不像在車(chē)床上那么方面。由于車(chē)床也能夠用來(lái)鉆孔和鉸孔，車(chē)床的多功能特性允許工件在一次裝夾中進(jìn)行多種操作。因此，在生產(chǎn)中使用的各種類型的車(chē)床比其他任何種類機(jī)床都要多。
車(chē)床的基本組成部分有：床身、主軸箱部件、尾架部件、絲杠和光杠。
床身是車(chē)床的主要組成部分。它通常是經(jīng)過(guò)正火處理或者球墨鑄鐵制成，其他所有基本部件都安裝在床身上。在床身上通常有兩組平行的導(dǎo)軌，有些制造廠全部四條導(dǎo)軌采用三角形導(dǎo)軌，而有些制造廠在一組或兩組中采用一個(gè)三角形導(dǎo)軌和一個(gè)矩形導(dǎo)軌，導(dǎo)軌經(jīng)過(guò)精密加工以保證其精度。大多數(shù)現(xiàn)代機(jī)床的導(dǎo)軌是經(jīng)過(guò)表面淬硬的，但在操作時(shí)還是應(yīng)該小心，以避免導(dǎo)軌受到損壞。導(dǎo)軌的任何誤差通常意味著整個(gè)機(jī)床的精度收到破壞。
主軸箱安裝在內(nèi)導(dǎo)軌的固定位置上，通常在床身的左側(cè)。它提供動(dòng)力并可以使工件以不同速度旋轉(zhuǎn)。大多數(shù)機(jī)床有8～18種轉(zhuǎn)速，通常以等比數(shù)列排列，而且現(xiàn)代車(chē)床只需移動(dòng)2～4個(gè)手柄就能得到全部轉(zhuǎn)速。一種不斷增長(zhǎng)的趨勢(shì)是通過(guò)電氣或者機(jī)械裝置來(lái)進(jìn)行無(wú)級(jí)變速。
由于機(jī)床的精度很大依賴于主軸，所以主軸的尺寸比較大，通常安裝在圓錐滾子軸承和球軸承中，主軸中有一個(gè)穿過(guò)整個(gè)主軸的長(zhǎng)孔，通過(guò)這個(gè)孔長(zhǎng)棒料可以送料，當(dāng)工件必須通過(guò)主軸孔送料時(shí)，確定了能夠被加工的棒料的最大尺寸。
尾架部件主要有三部分組成，底板與床身的內(nèi)導(dǎo)軌配合著，并可以在導(dǎo)軌上做縱向移動(dòng)，底板上有一個(gè)可以是整個(gè)尾架加緊在任何位置的裝置。尾架固定在底板上可以在某種類型鍵槽的底板上橫向移動(dòng)，可以允許尾架與主軸箱中的主軸對(duì)正。這是一個(gè)直徑通常大約在51～76mm（2～3英寸）之間的空心鋼制圓柱體，通過(guò)手輪和螺桿，尾架套筒可以在尾架中移入和移出幾英寸。
車(chē)床的規(guī)格被設(shè)計(jì)成兩個(gè)尺寸，第一個(gè)被稱為車(chē)床床面上最大加工直徑。這是在車(chē)床上所能旋轉(zhuǎn)的工件的最大直徑，它大約是兩項(xiàng)頂尖連線和導(dǎo)軌上最近點(diǎn)之間距離的兩倍，第二個(gè)規(guī)格尺寸是兩頂尖之間的最大距離，車(chē)床床面的最大加工直徑表示在車(chē)床上能夠車(chē)削的最大工件直徑，而兩頂尖之間的最大距離表示的是兩頂尖之間能夠安裝的工件的最大長(zhǎng)度。
普通車(chē)床是最經(jīng)常使用到的車(chē)床種類。它們具有前面介紹的所有那些部件的重型機(jī)床，并且除了小刀架之外，全部刀具的運(yùn)動(dòng)都有機(jī)會(huì)進(jìn)給。它們通常的尺寸：車(chē)床床面上的最大加工直徑為305～610mm（12～24英寸）；兩頂尖之間的距離為610～1219mm（24～48英寸）。但是，車(chē)床床面上最大加工直徑達(dá)到1270mm（50英寸）和兩頂尖距離達(dá)到3658mm（12英尺）的車(chē)床也并不少見(jiàn)。這些車(chē)床大多數(shù)都有切削盤(pán)和一個(gè)內(nèi)置冷卻循環(huán)系統(tǒng)。較小的普通車(chē)床，車(chē)床床面的最大加工直徑一般不超過(guò)330mm（13英寸），其中一些也能夠被設(shè)計(jì)成臺(tái)式車(chē)床，即床身可安裝在工作臺(tái)或者柜子上。
雖然普通車(chē)床功能很強(qiáng)大，有很多用途，由于更改和設(shè)置調(diào)整刀具及對(duì)工件進(jìn)行測(cè)量需要花費(fèi)大量時(shí)間，所以它們不適合批量生產(chǎn)。通常情況下，它們的實(shí)際加工時(shí)間要少于總時(shí)間的30%。此外，需要熟練的操作工人來(lái)操作所需要的所有操作，這種人工資很高而且往往供不應(yīng)求。然而操作工人的大部分時(shí)間卻花費(fèi)在簡(jiǎn)單的重復(fù)勞動(dòng)和觀察切削過(guò)程中。因此，為了減少或者完全不顧用這類熟練操作工人，轉(zhuǎn)塔車(chē)床、螺紋加工車(chē)床和其他類型的自動(dòng)或半自動(dòng)車(chē)床已經(jīng)很好的研制了出來(lái)并在生產(chǎn)制造中得到了廣泛的應(yīng)用。
2、數(shù)字控制
先進(jìn)制造技術(shù)中一個(gè)最基本的概念就是數(shù)字控制。在數(shù)控技術(shù)出現(xiàn)之前，所有的機(jī)床都是由人工操縱和控制的。在人工操縱機(jī)床的很多限制中，操作者技能的限制是一個(gè)最突出的問(wèn)題。采用人空控制時(shí)，產(chǎn)品的質(zhì)量直接和操作者的技能有關(guān)，數(shù)字控制代表了從人工控制走出來(lái)的第一步。
數(shù)字控制意味著采用預(yù)先錄制和存儲(chǔ)的指令來(lái)控制機(jī)床和其他制造系統(tǒng)。一個(gè)數(shù)控工程師的不是去操作一臺(tái)機(jī)床而是編寫(xiě)出能夠發(fā)出機(jī)器操作指令的程序。對(duì)于一臺(tái)數(shù)控機(jī)床，上面必須安裝有一個(gè)叫做閱讀機(jī)的裝置，用于接收和解碼編程指令。
數(shù)控技術(shù)的發(fā)展是為了克服人工操作的局限性，并且它已經(jīng)很好地這么做了。數(shù)字控制的機(jī)器比人工操縱的機(jī)器有更高的精度，生產(chǎn)出的零件一致性更好，生產(chǎn)速度更快，而且長(zhǎng)期工藝成本更低。數(shù)控技術(shù)的發(fā)展導(dǎo)致了制造技術(shù)中其他幾項(xiàng)發(fā)明創(chuàng)新的產(chǎn)生：
電火花加工技術(shù)，激光切割，電子束焊接。
數(shù)字控制還使得機(jī)床比它們?nèi)丝詹倏v的前輩們的用途更為廣泛。一臺(tái)數(shù)控機(jī)床能夠自動(dòng)生成很多種零件，每一個(gè)零件都有各種不同的復(fù)雜的加工過(guò)程。數(shù)字可以使生產(chǎn)廠家承擔(dān)那些對(duì)于采用人工控制的機(jī)床和工藝來(lái)說(shuō)，在經(jīng)濟(jì)上是不劃算的產(chǎn)品生產(chǎn)任務(wù)。
同很多先進(jìn)技術(shù)一樣，數(shù)控技術(shù)誕生于麻省理工學(xué)院的實(shí)驗(yàn)室里。數(shù)控這個(gè)概念是在20世紀(jì)50年代初在美國(guó)空軍的資助下提出的。在最初階段，數(shù)控機(jī)床只能夠做出有效的直線切割。
然而，曲線加工在機(jī)床加工中是一個(gè)難題，在編程時(shí)應(yīng)該采用橫向與豎向的一系列步驟來(lái)生成一個(gè)曲線，構(gòu)成步驟的直線越短，曲線就越光滑。步驟中的每一個(gè)線段都必須經(jīng)過(guò)計(jì)算。
這個(gè)問(wèn)題導(dǎo)致了1959年自動(dòng)編程（APT）語(yǔ)言的誕生。這是一門(mén)專門(mén)用于數(shù)控的編程語(yǔ)言，它使用一種特殊的類似英文符號(hào)的語(yǔ)言來(lái)定義幾何零件，描述切削是刀具的形狀和規(guī)定必要的運(yùn)動(dòng)。APT編程語(yǔ)言的發(fā)展是在數(shù)控技術(shù)進(jìn)一步發(fā)展中的一大進(jìn)步。那時(shí)候的機(jī)床只有硬線邏輯電路，指令程序被寫(xiě)在穿孔紙帶上，后來(lái)它被塑料帶所取代。帶閱讀機(jī)被用來(lái)把寫(xiě)在紙帶上的的指令給機(jī)器翻譯出來(lái)，所有的這一切都代表了機(jī)床數(shù)控的巨大進(jìn)步。然而，在數(shù)控發(fā)展的這個(gè)階段還是有很多問(wèn)題。
一個(gè)主要問(wèn)題就是打孔紙帶的易碎壞性。在機(jī)械加工過(guò)程中，載有程序指令的紙帶斷裂或者被撕裂是一件很常見(jiàn)的事情。在機(jī)床上每加工一個(gè)零件，都需要將載有程序指令的紙帶放入閱讀機(jī)中重新運(yùn)行一次，因此，這個(gè)問(wèn)題變得更加嚴(yán)重。如果需要制造100個(gè)某種零件，則要將紙帶通過(guò)閱讀機(jī)100次。脆弱的紙帶根本無(wú)法承受這樣殘酷的車(chē)間環(huán)境和這種重復(fù)使用。
這就導(dǎo)致了一種磁性膠帶的發(fā)展，在紙帶上通過(guò)一系列的小孔來(lái)載有編程指令，在塑料膠帶上通過(guò)采用一系列的磁點(diǎn)來(lái)載有編程指令。塑料紙帶的強(qiáng)度要比紙質(zhì)紙帶的強(qiáng)度要強(qiáng)很多，這就解決了常見(jiàn)的斷裂和撕裂問(wèn)題。然而，仍然有兩個(gè)問(wèn)題。
其中最重要的一個(gè)問(wèn)題是很難或者說(shuō)幾乎不可能修改磁帶上輸入的指令。即使對(duì)指令程序進(jìn)行很輕微的調(diào)整，也有必要中斷加工并制作一條新帶。而且?guī)ㄟ^(guò)閱讀器的速度必須要和加工的零件個(gè)數(shù)相同。幸運(yùn)的是，計(jì)算機(jī)技術(shù)已經(jīng)變成現(xiàn)實(shí)，并且很快地解決了數(shù)控加工與穿孔紙帶和塑料紙帶相關(guān)的問(wèn)題。
在形成了直接數(shù)字控制（DNC）這個(gè)概念之后，可以不再采用紙帶或塑料帶作為編程指令的載體，這樣就解決了與之有關(guān)的問(wèn)題。在直接數(shù)字控制中，機(jī)床通過(guò)數(shù)據(jù)傳輸線路連接到一臺(tái)主計(jì)算機(jī)上。操縱這臺(tái)機(jī)床所需要的程序都存儲(chǔ)在主計(jì)算機(jī)中，當(dāng)需要時(shí)，通過(guò)數(shù)據(jù)傳輸線路提供給每臺(tái)機(jī)床。直接數(shù)字控制在穿孔紙帶和塑料紙帶的基礎(chǔ)上邁出了一大步。然而，它有著同其他依賴于主計(jì)算機(jī)技術(shù)一樣的限制性。當(dāng)主計(jì)算機(jī)發(fā)生故障時(shí)，由其控制的所有機(jī)床也會(huì)停止工作。這個(gè)問(wèn)題導(dǎo)致了計(jì)算機(jī)數(shù)控的發(fā)展。
3、車(chē)削加工
普通車(chē)床作為最古老的切削車(chē)床之一，目前仍然有很多有用的和重要的特性。現(xiàn)在，這些機(jī)床主要用于一些小規(guī)模的工廠中，進(jìn)行小批量的生產(chǎn)而不是進(jìn)行大規(guī)模的量產(chǎn)。
在現(xiàn)在的生產(chǎn)車(chē)間中普通車(chē)床已經(jīng)被種類繁多的自動(dòng)車(chē)床所代替，比如自動(dòng)仿形車(chē)床?，F(xiàn)在，實(shí)用這種加工方法的生產(chǎn)速度和工廠中使用的最快的加工設(shè)備的速度相等。
普通車(chē)床的公差主要依賴于操作工人的熟練程度。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)件重新設(shè)計(jì)成生產(chǎn)零件時(shí)，應(yīng)選用經(jīng)歷的公差。
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，設(shè)計(jì)人員應(yīng)盡量將加工工序的數(shù)量減到最小。
自動(dòng)螺絲車(chē)床 一般來(lái)說(shuō)，自動(dòng)螺絲車(chē)床分為以下幾種：?jiǎn)屋S自動(dòng)、多軸自動(dòng)和自動(dòng)加緊車(chē)床。自動(dòng)螺絲車(chē)床最初被用來(lái)對(duì)螺釘和類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0.05mm。對(duì)于某些零件，槽寬的公差可以達(dá)到0.125mm。鏜孔和休用單刃刀具進(jìn)行精加工時(shí)，公差可達(dá)到0.0125mm。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0.125mm是經(jīng)濟(jì)的。
附件2：外文原文
NC control and cutting
1 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 components 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 components 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 V-shape for all four ways, whereas others utilize one inverted V and one flat way in one or both sets, They are precision-machined to assure accuracy of alignment. On most modern lathes the way are surface-hardened 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 gears-similar 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 machined when the material must be fed through spindle.
The tailsticd assembly consists, essentially, of three parts. A lower casting fits on the inner ways of the bed and can slide longitudinally thereon, with a means for clamping the entire assembly in any desired location, An upper casting fits on the lower one and can be moved transversely upon it, on some type of keyed ways, to permit aligning the assembly is the tailstock quill. This is a hollow steel cylinder, usually about 51 to 76mm(2to 3 inches) in diameter, that can be moved several inches longitudinally in and out of the upper casting by means of a hand wheel and screw.
The size of a lathe is designated by two dimensions. The first is known as the swing. This is the maximum diameter of work that can be rotated on a lathe. It is approximately twice the distance between the line connecting the lathe centers and the nearest point on the ways, The second size dimension is the maximum distance between centers. The swing thus indicates the maximum work piece diameter that can be turned in the lathe, while the distance between centers indicates the maximum length of work piece that can be mounted between centers.
Engine lathes are the type most frequently used in manufacturing. They are heavy-duty machine tools with all the components described previously and have power drive for all tool movements except on the compound rest. They commonly range in size from 305 to 610 mm(12 to 24 inches)swing and from 610 to 1219 mm(24 to 48 inches) center distances, but swings up to 1270 mm(50 inches) and center distances up to 3658mm(12 feet) are not uncommon. Most have chip pans and a built-in coolant circulating system. Smaller engine lathes-with swings usually not over 330 mm (13 inches ) –also are available in bench type, designed for the bed to be mounted on a bench on a bench or cabinet.
Although engine lathes are versatile and very useful, because of the time required for changing and setting tools and for making measurements on the work piece, thy are not suitable for quantity production. Often the actual chip-production tine is less than 30% of the total cycle time. In addition, a skilled machinist is required for all the operations, and such persons are costly and often in short supply. However, much of the operator’s time is consumed by simple, repetitious adjustments and in watching chips being made. Consequently, to reduce or eliminate the amount of skilled labor that is required, turret lathes, screw machines, and other types of semiautomatic and automatic lathes have been highly developed and are widely used in manufacturing.
2 Numerical Control
One of the most fundamental concepts in the area of advanced manufacturing technologies is numerical control (NC). Prior to the advent of NC, all machine tools ere manually operated and controlled. Among the many limitations associated with manual control machine tools, perhaps none is more prominent than the limitation of operator skills. With manual control, the quality of the product is directly related to and limited to the skills of the operator. Numerical control represents the first major step away from human control of machine tools.
Numerical control means the control of machine tools and other manufacturing systems through the use of prerecorded, written symbolic instructions. Rather than operating a machine tool, an NC technician writes a program that issues operational instructions to the machine tool. For a machine tool to be numerically controlled, it must be interfaced with a device for accepting and decoding the programmed instructions, known as a reader.
Numerical control was developed to overcome the limitation of human operators, and it has done so. Numerical control machines are more accurate than manually operated machines, they can produce parts more uniformly, they are faster, and the long-run tooling costs are lower. The development of NC led to the development of several other innovations in manufacturing technology:
Electrical discharge machining,Laser cutting,Electron beam welding.
Numerical control has also made machine tools more versatile than their manually operated predecessors. An NC machine tool can automatically produce a wide of parts, each involving an assortment of widely varied and complex machining processes. Numerical control has allowed manufacturers to undertake the production of products that would not have been feasible from an economic perspective using manually controlled machine tolls and processes.
Like so many advanced technologies, NC was born in the laboratories of the Massachusetts Institute of Technology. The concept of NC was developed in the early 1950s with funding provided by the U.S. Air Force. In its earliest stages, NC machines were able to made straight cuts efficiently and effectively.
However, curved paths were a problem because the machine tool had to be programmed to undertake a series of horizontal and vertical steps to produce a curve. The shorter the straight lines making up the steps, the smoother is the curve, Each line segment in the steps had to be calculated.
This problem led to the development in 1959 of the Automatically Programmed Tools (APT) language. This is a special programming language for NC that uses statements similar to English language to define the part geometry, describe the cutting tool configuration, and specify the necessary motions. The development of the APT language was a major step forward in the fur ther development from those used today. The machines had hardwired logic circuits. The instructional programs were written on punched paper, which was later to be replaced by magnetic plastic tape. A tape reader was used to interpret the instructions written on the tape for the machine. Together, all of this represented a giant step forward in the control of machine tools. However, there were a number of problems with NC at this point in its development.
A major problem was the fragility of the punched paper tape medium. It was common for the paper tape containing the programmed instructions to break or tear during a machining process. This problem was exacerbated by the fact that each successive time a part was produced on a machine tool, the paper tape carrying the programmed instructions had to be rerun through the reader. If it was necessary to produce 100 copies of a given part, it was also necessary to run the paper tape through the reader 100 separate tines. Fragile paper tapes simply could not withstand the rigors of a shop floor environment and this kind of repeated use.
This led to the development of a special magnetic plastic tape. Whereas the paper carried the programmed instructions as a series of holes punched in the tape, the plastic tape carried the instructions as a series of magnetic dots. The plastic tape was much stronger than the paper tape, which solved the problem of frequent tearing and breakage. However, it still left two other problems.
The most important of these was that it was difficult or impossible to change the instructions entered on the tape. To made even the most minor adjustments in a program of instructions, it was necessary to interrupt machining operations and make a new tape. It was also still necessary to run the tape through the reader as many times as there were parts to be produced. Fortunately, computer technology became a reality and soon solved the problems of NC associated with punched paper and plastic tape.
The development of a concept known as direct numerical control (DNC) solved the paper and plastic tape problems associated with numerical control by simply eliminating tape as the medium for carrying the programmed instructions. In direct numerical control, machine tools are tied, via a data transmission link, to a host computer. Programs for operating the machine tools are stored in the host computer and fed to the machine tool an needed via the data transmission linkage. Direct numerical control represented a major step forward over punched tape and plastic tape. However, it is subject to the same limitations as all technologies that depend on a host computer. When the host computer goes down, the machine tools also experience downtime. This problem led to the development of computer numerical control.
3 Turning
The engine lathe, one of the oldest metal removal machines, has a number of useful and highly desirable attributes. Today these lathes are used primarily in small shops where smaller quantities rather than large production runs are encountered.
The engine lathe has been replaced in today’s production shops by a wide variety of automatic lathes such as automatic of single-point tooling for maximum metal removal, and the use of form tools for finish on a par with the fastest processing equipment on the scene today.
Tolerances for the engine lathe depend primarily on the skill of the operator. The design engineer must be careful in using tolerances of an experimental part that has been produced on the engine lathe by a skilled operator. In redesigning an experimental part for production, economical tolerances should be used.
Turret Lathes Production machining equipment must be evaluated now, more than ever before, this criterion for establishing the production qualification of a specific method, the turret lathe merits a high rating.
In designing for low quantities such as 100 or 200 parts, it is most economical to use the turret lathe. In achieving the optimum tolerances possible on the turrets lathe, the designer should strive for a minimum of operations.
Automatic Screw Machines Generally, automatic screw machines fall into several categories; single-spindle automatics, multiple-spindle automatics and automatic chucking machines. Originally designed for rapid, automatic production of screws and similar threaded parts, the automatic screw machine has long since exceeded the confines of this narrow field, and today plays a vital role in the mass production of a variety of precision parts. Quantities play an important part in the economy of the parts machined on the automatic screw machine. Quantities less than on the automatic screw machine. The cost of the parts machined can be reduced if the minimum economical lot size is calculated and the proper machine is selected for these quantities.
Automatic Tracer Lathes Since surface roughness depends greatly on material turned, tooling , and feeds and speeds employed, minimum tolerances that can be held on automatic tracer lathes are not necessarily the most economical tolerances.
In some cases, tolerances of 0.05mm are held in continuous production using but one cut . groove width can be held to 0.125mm on some parts. Bores and single-point finishes can be held to 0.0125mm. On high-production runs where maximum output is desirable, a minimum tolerance of 0.125mm is economical on both diameter and length of turn.