计算机辅助制造讲义-2007-2演示文稿.PPT

Chapter 5:Fundamentals of Numerical Control 5.1 Historical Development/历史演变 It has been over 50 years since … In 1947, a jig borer (坐标镗床)that was coupled with a computer was developed In 1949, a prototype of a programmable milling machine was developed In 1952, a modified three-axis milling machine was demonstrated 5.1 Historical Development/历史演变 Since then, many improvements, in the machine and in the control have been made. NC machine tool/数控机床 Turning center/车削中心 Machining center/加工中心 Mill-turn center/车铣复合加工中心 High-speed machine tool/高速切削机床 Vertical Machining center/立式加工中心 Machining centers and turning centers can perform multiple machining processes Machining center/加工中心 Mill-turn center/车铣复合加工中心 Mill-turn center/车铣复合加工中心 High-speed machine tool/高速切削机床 Three high high-speed spindle: >20,000 rpm high-feed-rate drives: >600 ipm high precision: <0.0001-in accuracy 5.1 Historical Development/历史演变 Position/地位 The invention of the NC machine tool is a major technological evolution in manufacturing. NC is the foundation for many modern manufacturing technologies 5.2 PRINCIPLES OF NUMERICAL CONTROL /数控原理 Definition of NC/定义 “a system in which actions are controlled by direct insertion of numerical data at some point. The system must automatically interpret this data.” ----Electronic Industries Association (EIA) 5.3 CLASSIFICATION OF NUMERICAL CONTROL/数控类型 Motion control: point to point (PTP) continuous (contouring) path Control loops: open loop and closed loop Power drives: hydraulic, electric, pneumatic Positioning systems: incremental positioning absolute positioning Hardware and software: Hardware NC software computer numerical control (CNC) 5.3.5 NC and CNC Hardware NC: vacuum-tube circuit(电子管电路) transistor(晶体管), relay(继电器) Computer numerical control (CNC) Since the 1980s, no hardwired NCs have been produced. T