NC and CNC
数控技术
The History of NC and CNC Development
数字控制与计算机数字控制的发展历史
Numerical Control (NC) is any machining process in which the operations are executed automatically in quences as specified by the program that contains the information for thejewellery tool movements. The NC concept was propod in the late 1940s by John Parsons of Traver City, Michigan. Parsons recommended a method of automatic machine control that would guide a milling cutter to produce a "thru-axis curve" in order to generate smooth profiles on work pieces.
数字控制是按照含有机床(刀具)运动信息程序所指定的顺序自动执行操作的加工过程。数控这一概念是由密歇根洲特拉华城的约翰·帕森于20世纪四十年代后期提出的。为了在工件上加工光滑的轮廓，帕森提出了一种自动的机床控制方式，它能够引导铣床刀具加工出一种“过轴
曲线”。
In 1949, The U.S. Air Force awarded Parsons a contract to develop a new type of machine tool that would be able to speed up production methods. Parsons wayscommissioned the Massachutts Institute of Technology (M.I.T.) to develop a practical implementation of his concept. Scientists and engineers at M.I.T. built a control system for a two-axis milling machine that ud a perforated paper tape as the input media. In a short period of time, all major machine tool manufacturers were producing some machines with NC, but it was not until the late 1970s that computer-bad NC became widely ud. NC matured as an automation technology when inexpensive and powerful microprocessors replaced hard-wire trafflogic-making computer-bad NC systems.
1949年，美国空军与帕森签署了合同，要求开发一种能够提高生产率的新型机床。帕森委托麻省理工学院(MIT)来开发一种新概念机床，麻省理工学院的科学家和工程师研制出了一种用穿孔纸带作为输入媒介的二轴联动铣床控制系统。在较短时间内，当时所有主要的机床生产商都生产了一些数控机床，但直到20世纪七十年代后期，基于计算机的数字控制才
被得到广泛的使用。只有价格低廉且功能强大的微处理芯片代替了计算机数控系统中的硬连线逻辑发生器后，NC才真正成为一门自动化技术。
When Numerical Control is performed under computer supervision, it is called Computer Numerical Control (CNC). Computers are the control units of CNC machines, they are built in or linked to the machines via communications channels. When a programmer input some information in the program by tape and so on, the computer calculates all 想象力英语>babylonnecessary data to get the job done.
当数控机床在计算机监控下工作时，它就被称为计算机数控机床(CNC)。计算机是CNC机床的控制单元，它们内嵌于数控机床或者通过通讯渠道与数控机床联接，当程序员编程时，通过纸带或磁盘将一些信息输入，计算机将对一些必要的数据进行计算的完成工作。
On the first Numerically Controlled (NC) machines were controlled by tape, and
becau of that, the NC systems were known as tape-controlled machines. They were able to control a single operation entered into the machine by punched or magnetic tape.
There was no possibility of editing the program on the machine. To change the program, a new tape had to be made.
在线中译英
由于第一台数控机床的数据是由纸带控制的，因此数控系统被称为纸带控制机床。它们只能控制由输入到机床内的纸带或磁带所规定的单一操作，输入到机床内的程序是不能被编辑的，要改变程序必须重做新纸带。
Today's systems have computers to control data; they are called Computer Numerically Controlled (CNC) machines. For both NC and CNC systems, work principles are the same. Only the way in which the execution is controlled is different. Normally, new systems are faster, more powerful, and more versatile
当今的系统都由计算机来控制数据，因而称之为计算机数控机床(简称CNC机床)。NC和CNC系统两者的工作原理一样，仅仅控制执行的方式不同。新型的数控系统通常速度更快、功率更大、功能更齐全。彼岸花的英文
The Applications of NC/CNC
数字控制与计算机数字控制的应用
Since its introduction, NC technology has found many applications, including lathes and turning Centers, milling machines and machining centers , punches , electrical discharg machines(EDM) Flame cutters,grinders,and inspection equipment. the most complex CNC machine tools are the turning center,shown in Fig.4-1(Amodern turning center with a ten-station turret that accepts quick-chang tools.Each tool can be positioned in Seconds with the press of a button).And the machine center shown in Fig.4-2(Vertical machining center,the tool magazine is on the machine.the control panel on the right can be swiveled by the operator)and Fig.4-3(horizontal machining center,equipped with an automatic tool changer .tool magazines can store 200 ctting tools.
数控技术自创立以来就得到了广泛的应用，包括车床和车削中心、铣床和加工中心、冲床、电火花(EDM)加工机床、线切割机床、磨床以及测试检测装置等。最复杂的计算机数控机床是车削中心，图4—1所示一个具有十转位的刀架能进行快速换刀的现代车削中心，立式加工中心如图4—2所示(刀具库在机床的左边。右边的控制面板可由操作者通过转臂转
动)，以及卧式加工中心，通过按下按钮每把刀可在数秒钟内定位。如图4—3所示(配有自动换刀系统。刀具库储备有200把切削工具)。
When preparing a progam for a particular operation ,the prommer must lect all cutting data using recommendations for conventional machining .this includes proper
Selection of cutting speeds,feedrate,tools and tool geometry,and so on.when the programmer has chon all of the necessary information properly,the operator loads the programme into the machine and press a button to start the cutting crycle .the CNC machine moves automatically from one maching operation to another , changing the cutting tols and applying the coolent.in a surprisingly short time ,the workpiece is
Machined according to the highest quality stangards. But that is matter how big the work ries is,all of the parts will be almost identical in size and surface finishing. At this time of advanced technology,with its high demands for surface finishing and tolerances of components in,for example ,aerospace,nuclear,and medical equipment manufacturing,only CNC machines provide successful results.
当为某项操作编程时，程序员必须选择传统的加工切削数据推荐值。这些切削数据包括切削速度、进给率、刀具和刀具几何形状等。当程序员正确选择所有必要信息后，操作人员祖国在我心中演讲稿将程序载入机床并按下按钮，切削循环就开始。
Numerical control (NC) is a form of programmable automation in which the processing equipment is controlled by means of numbers, letters, and other symbols. The numbers, letters, 浙江大学2013年录取分数线and symbols are coded in an appropriate format to define a program of instructions for a学习体会 particular workpart or job. The instructions are provided by either of the two binary coded decimal systems: the Electronic Industries Association (EIA) code, or the American Standard Code for Information Interchange (ASCII). ASCII-coded machine control units will not accept . EIA coded instructions and vice versa. Increasingly, however, control units are being made to accept instructions in either code. 121Automation operation by NC is readily adaptable to the
