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A016 基于 840 曲轴 数控系统 设计 应用

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湖北汽车工业学院（英文翻译） 毕 业 设 计（英文翻译）题 目：Introduction to Numerical Control Machining系 别：xx专 业：xx班 级：XX学生姓名：XX学 号：XX指导教师：XX6Introduction to Numerical Control MachiningHistorical perspective The development of numerical control owes much to the United States air force,whichrecognized the need to develop more efficient manufacturing methods for modern aircraft. Following World War II, the components used to fabricate jet aircraft became more complex and required more machining. Most of the machining involved milling operations,so the Air Force sponsered a research project at Massachusetts Institue of Technology to develop a prototype NC milling machine. This prototype was produced by retrofitting a conventional tracer mill with numerical control servomechanisms for the three axes of the machine. In March 1952, the MITLabs held the first demonstration of the NC machine.The machine tool builders gradually began developing their own projects to introduce commercial NC units. Also,certain industry users, especially airframe builders,worked to devise numerical control machines to satisfy their own particular production needs.The Air force continued its encouragement of NC development by sponsoring additional research at MIT to design a part programming language that could be used in controlling N.C. machines. What is Numerical Control ? Numerical control can be defined as a form of programmable automation in which process is controlled by numbers,letters and symbols. In NC,the numbers form a programme of instructions designed for a particular workpart or job. When job changes the program of instruction changes. This capability to change a program for each new job gives NC its flexibilty. Numerical control should be considered as a possible mode of controlling the operation for any production situation possesing the following characteristics : Similar workparts in terms of raw material (e.g. metal shock for machining) The work parts are produced in various sizes and geometries. The workparts are produced in batches of small to medium size quantities. A sequence of similar processing steps is required to complete the operation on each workpiece. Many machining jobs meet these conditions. The machined workparts are metal, they are specified in many different sizes and shapes,nad most machined parts produced in the industry today are made in small to medium size lots sizes. To produce each parts a sequence of drilling operations may be required ar aseries of turning or milling operations. The suitability of NC for these kinds of jobs is the reason of tremendous growth of numerical control in metal working industry over the last 25 years. Basic components of NC system An operational numerical control system consists of the following three basic components: 1. Program of instructions. 2. Controller unit, also called machine tool unit. 3. Machine tool or other controlled process. The program of instructions serves as input to the controller unit, which in turn commands the machine tool or other process to be controlled. Program of Instructions. The program of instructions is the detailed step by step set of instructions which tell the machine what to do. It is coded in numerical or symbolic form on some type of input medium that can be interpreted by the controller unit. The most common one is the 1-inch-wide punched tape. Over the years,other forms of input media has been used,including punched cards, magnetic tape, and even 35mm motion picturefilm. There are two other methods of input to the NC system which should be mentioned. The first is by manual entry of instructional data to the controller unit. This is time consuming and is rarely used except as an auxillary means of control or when one or a very limited no. of parts to be made. The second method of input is by means of a direct ling with the computer. This is called direct numerical control, or DNC. Controller Unit The second basic component of NC system is the controller unit. This consists of electronics and hardware that read and interpret the program of instructionsand convert it to mechanical actions of the machine tool. The typical elements of the controller unit include the tape reader, a data buffer, signal output channels to the machine tool,and the sequencecontrols to coodinate the overall operationof the foregoing elements. The tape reader is an electrical-mechanical device for the winding and reading the punched tape containing the program of instructions. The signal output channels are connected to the servomotores and other controls in machine tools. Most N.C. tools today are provided with positive feedback controls for this purposeand are referred as closed loop systems. However there has been growth in the open loop systems which do not make use of feedback signals to the controller unit. The advocates of the open loop concept claim that the realiblity of the system is great enough that the feedback controls are not needed. Machine Tool The third basic component of an NC system is the machine tool or other controlled process. It is part of the NC system which performs useful work. In the most common example of an NC system,one designed to perform machining operations, The machine tool consists of the worktable and spindle as well as the motorsand controls necessary to drive them. It also includesthe cutting tools,work fixtures and other auxillary equipment needed in machining operation.数控加工介绍历史观点数控的发展很大一部分应归功于美国空军，它意识到了有要为现代航空器开发提供更加有效的制造方法的需要。而在接下来的第二次世界大战中，用来制作喷气式飞机的元件变得越来越复杂并且需要有更多加工。这些加工的大部分操作包括磨削，因此空军部在麻省理工大学（MIT）发起了一项开发一个NC磨床原型的研发工程。这个原型是通过使用一个传统的磨床和一个用数控伺服系统来控制这个机器的三个刀片来制作的。在1952年的三月，麻省理工大学实验室主持了对第一台数控机床的示例。这台机器的制作者们一步步的开始了他们自己的工程，这些工程是用来引入商业性数控元件。同时，一些工业上的用户，特别是作机身构架设计的用户，为了满足他们自己的特别的用途而参入了进来，并且开始设计适合他们的数控机床。空军军方继续对数控机床的开发作出奖励，它在MIT发起了另外一项研发工程，用来开发一个用于对数控机床进行操作，控制的数控编程语言。什么是数控（Numerical Control）？数控可以定义为是这样的一种自动化的可编程的形式，它的整个过程是由数字，字母和各种字符来控制的。在数控（NC）里，这些数字形成一系列的针对一个特殊的工作部分或任务而设计的编程指。当要完成的任务改变时，相应的程序指令也要发生改变。数控的这种为每个新的任务只需要改变一个程序的能力，让它的应用变得十分有弹性。数控机床应该被认为是作为一种可能的控制模式，在这种模式里它能控制具有以下的特性的、对其相类似的所有产品形式处理的操作：在有相同的加工部分的原材料的形式（例如：加工金属的冲压）。要加工的部分的生产有各种各样的大小和形态要求。要加工的部分的生产是中小型的数量的批处理。要每个工件上都要进行的一系列按照顺序来进行的相同的处理步骤。许多的加工任务都符合上述的条件。这些机床加工的部分是金属，它们的各有各的特性，无论是在大小上，还是在形状上，并且现在的大部分的工业上在机床加工的部分从小型到中型，乃至各种各样的型号。在生产每一个部分的过程中，都有像如钻孔、锻造、磨削这样相同的操作。数控机床在这种形式的任务上有高效的适应性，这就成为了在过去的25年里，数控机床能在金属加工业有巨大的发展的原因。数控系统的基本组成元件一个可操作的数控系统由以下三个基本部分组成：4.由一系列指令构成的程序。5.控制单元，也叫做加工工具单元（machine tool unit）。6.加工工具或者其他的控制过程。指令程序用来作为控制单元的输入，而这些输入的指令控制着加工工具或者其他的加工过程。编程指令编程指令程序是对每一个加工步骤的详细指令集，它告诉机器都要干些什么。它是以一种数字或者是字符的形式表现出来的，在某种能够被控制单元所解