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数控技术(论文翻译)

  • 简介:(论文翻译 页数:10 字数:47920数字控制与计算机数字控制的发展历史 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...
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(论文翻译 页数:10 字数:47920数字控制与计算机数字控制的发展历史
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”。
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。
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。
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。
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。
数字控制与计算机数字控制的应用
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)。
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,操作人员将程序载入机床并按下按钮,切削循环就开始。

 

NC and CNC
The History of NC and CNC Development
Numerical Control (NC) is any machining process in which the operations are executed automatically in sequences as specified by the program that contains the information for the tool movements. The NC concept was proposed in the late 1940s by John Parsons of Traverse 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.
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 commissioned the Massachusetts 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 used 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-based NC became widely used. NC matured as an automation technology when inexpensive and powerful microprocessors replaced hard-wire logic-making computer-based NC systems.
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 necessary data to get the job done.
On the first Numerically Controlled (NC) machines were controlled by tape, and
because 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.
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

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