【正文】 anually operated predecessors. An NC machine tool can automatically produce a wide of parts, each involving an assortment of widely varied and plex 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.數(shù)字控制還使得機(jī)床比它們采用有人工操的前輩們的用途更為廣泛。數(shù)字控制的機(jī)器比人工操縱的機(jī)器精度更高、生產(chǎn)出零件的一致性更好、生產(chǎn)速度更快、而且長期的工藝裝備成本更低。對于一臺數(shù)控機(jī)床，其上必須安有一個被稱為閱讀機(jī)的界面裝置，用來接受和解譯出編程指令。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.數(shù)字控制意味著采用預(yù)先錄制的、存儲的符號指令來控制機(jī)床和其他制造系統(tǒng)。采用人工控制是，產(chǎn)品的質(zhì)量直接與操作者的技能有關(guān)。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。第二章 2 Numerical ControlOne 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.然而，操作工人的大部分時間卻花費(fèi)在簡單的重復(fù)調(diào)整和觀察切屑過程上。通常，它們的實(shí)際加工時間少于其總加工時間的30%。小型的普通車床—車床床面最大加工直徑一般不超過330mm（13英寸）被設(shè)計成臺式車床，其床身安裝在工作臺或柜子上。它們的規(guī)格通常是：車床床面上最大加工直徑為305~610mm（12~24英寸）；但是，床面上最大加工直徑達(dá)到1270mm（50英寸）和兩頂尖之間距離達(dá)到3658mm的車床也并不少見。Engine lathes are the type most frequently used in manufacturing. They are heavyduty machine tools with all the ponents described previously and have power drive for all tool movements except on the pound rest. They monly 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 unmon. Most have chip pans and a builtin coolant circulating system. Smaller engine latheswith 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.普通車床是生產(chǎn)中最經(jīng)常使用的車床種類。第二個規(guī)格尺寸是兩頂尖之間的最大距離。這是在車床上能夠旋轉(zhuǎn)的工件的最大直徑。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.車床的規(guī)格用兩個尺寸表示。它是一個直徑通常大約在51~76mm（2~3英寸）之間的鋼制空心圓柱體。尾座體安裝在底板上，可以沿某種類型的鍵槽在底板上橫向移動，使尾座能與主軸箱中的主軸對正。底板與床身的內(nèi)側(cè)導(dǎo)軌配合，并可以在導(dǎo)軌上作縱向移動。主軸孔的大小是車床的一個重要尺寸，因此當(dāng)工件必須通過主軸孔供料時，它確定了能夠加工的棒料毛坯的最大尺寸。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, thro