NUMERICAL CONTROL
Numerical control(N／C)is a form of programmable automation in which the processing equipment is controlled by means of numbers，letters，and other symbols．The numbers，letters，and symbols are coded in an appropriate format to define a program of instructions for a particular work part or job．When the job changes，the program of instructions is changed．The capability to change the program is what makes N／C suitable for low-and medium-volume production．It is much easier to write programs than to make major alterations of the processing equipment．
There are two basic types of numerically controlled machine tools：point—to—point and continuous—path(also called contouring)．Point—to—point machines use unsynchronized motors，with the result that the position of the machining head Can be assured only upon completion of a movement，or while only one motor is running．Machines of this type are principally used for straight—line cuts or for drilling or boring．
數(shù)控是可編程自動(dòng)化技術(shù)的一種形式，通過(guò)數(shù)字、字母和其他符號(hào)來(lái)控制加工設(shè)備。數(shù)字、字母和符號(hào)用適當(dāng)?shù)母袷骄幋a為一個(gè)特定工件定義指令程序。當(dāng)工件改變時(shí)，指令程序就改變。這種改變程序的能力使數(shù)控適合于中、小批量生產(chǎn)，寫(xiě)一段新程序遠(yuǎn)比對(duì)加工設(shè)備做大的改動(dòng)容易得多。
數(shù)控機(jī)床有兩種基本形式：點(diǎn)位控制和連續(xù)控制(也稱為輪廓控制)。點(diǎn)位控制機(jī)床采用異步電動(dòng)機(jī)，因此，主軸的定位只能通過(guò)完成一個(gè)運(yùn)動(dòng)或一個(gè)電動(dòng)機(jī)的轉(zhuǎn)動(dòng)來(lái)實(shí)現(xiàn)。這種機(jī)床主要用于直線切削或鉆孔、鏜孔等場(chǎng)合。
數(shù)控系統(tǒng)由下列組件組成：數(shù)據(jù)輸入裝置，帶控制單元的磁帶閱讀機(jī)，反饋裝置和切削機(jī)床或其他形式的數(shù)控設(shè)備。