Unit 24 Computerized Numerical Control 计算机化数字控制.pptVIP

Unit 24 Computerized Numerical Control 计算机化数字控制 Numerical Control 数控 This century has seen machinery become more automated, thereby（因此 从而） eliminating（消除 削减） machine-operator intervention（介入 干涉） in the manufacturing process. 本世纪机械变得更自动化，从而在制造过程中削减了机器操作人员的介入。 * Yet, as automation has increased, machines have become inherently（固有地 内在地） more specialized. 然而，由于自动化的增加，机器将变得更加专业化。 A highly automated machine that may turn out 20000 components per day，will generally be able to produce only a limited class of components. 一天可生产20000个零件的一台高度自动化的机器，通常能生产的零件种类是很有限的。 Until recently, prototypes（样品 典型） and low volume（量 体积 音量 卷） components were produced by manually operated conventional（传统的） machine tools. 直到最近，样品和小批量的零件仍由手工操作传统的机床来加工。 With the advent of（随着---的出现） new hard-to-machine materials and requirements for tolerances of a precision that can approach one part in ten thousand, the best human operators have reached the limited class（等级） of their ability. 伴随着新的难以加工的材料的出现以及精确度达到万分之一的（加工）误差的要求，最优秀的操作者已达到他们能力的极限。 These requirements, together with a need for component flexibility（适应性 灵活性 柔性）, have lead to a form of automatic machine control known by the generic（一般的 普通的） name numerical control (frequently abbreviated（缩写 缩略） NC in this text（课文 正文） and in engineering literature（文献资料 文学） generally). 这些要求以及对零件适应性的需要导致了一种自动化机器控制形式的产生，一般称其为数字控制（在本文和工程文献资料中经常缩写为NC）。 The history of NC began in the late 1940s, when John T. Parsons proposed that a method of automatic machine control be developed which would guide a milling cutter to generate a smooth curve. 数控的历史始于二十世纪四十年代末，John.T.Parson 提议研制一种自动化机器控制方法，该方法将引导铣刀形成光滑的曲线轨迹。 As he conceived（设想 想象） it , the coordinate points would be coded（编码） onto punched cards（穿孔卡片） fed to a machine controller which would cause a modified（改进 修改） milling machine to move in small incremental steps to achieve the desired path. 正如他所设想的，坐标点在穿孔卡片上被编码并送到机床控制器中，机床控制器使经改进的铣床以小增量步长运动从而得所需轨迹。 In 1949 the U.S. Air Force commissioned（委托） the servomechanisms Laboratory