數(shù)控技術(shù)概述(文件)
【正文】 ting tool to generate angular surfaces, twodimensional curves, or threedimensional contours in the workpiece, such as milling and turning operations. . Chapter 1 INTRODUCTION TO NUMERICAL CONTROL Types of NC Motion Control System Interpolation To cut along a circular path,the circle must be divided into a series of straightline segments that approximate the circular tool is manded to machine each line segment in succession so that the machined surface closely matches the desired shape. . Chapter 1 INTRODUCTION TO NUMERICAL CONTROL Types of NC ServoDrive System The principal function of NC is the positioning of the tool or the machine table in accordance with the programmed data. Industry has developed three different types of drives based on how the NC system acplishes positioning. These are the openloop（開環(huán)） , the closedloop（閉環(huán)） and half closedloop（半閉環(huán)） drive system. . Chapter 1 INTRODUCTION TO NUMERICAL CONTROL Types of NC ServoDrive System OpenLoop ServoDrive It is the simplest and least cost form of servodrive. It is characterized as a system that lacks feedback . That is , once an input control signal is sent , there is no sensing device to confirm the action of the control signal. Driving circuit Stepping motor Worktable Leadscrew Pulse train . Chapter 1 INTRODUCTION TO NUMERICAL CONTROL Types of NC ServoDrive System HalfClosedLoop ServoDrive It is characterized as a system that the indirect feedback monitors the output of this method is popular with NC systems, it is not as accurate as direct feedback, The halfclosedloop system pares the mand position signal with the drive signal of the servomotor. . Chapter 1 INTRODUCTION TO NUMERICAL CONTROL Types of NC ServoDrive System HalfClosedLoop ServoDrive Position pare circuit Speed control circuit Worktable Instruction Speed feedback signal Position feedback signal Leadscrew Servomotor . Chapter 1 INTRODUCTION TO NUMERICAL CONTROL Types of NC ServoDrive System ClosedLoop ServoDrive It is characterized as a system that the direct feedback monitors the output of servomotor. A feedback sensor directly measures the position of worktable. With its drive signal originated by the worktable, It is the preferred system because it monitors the actual position of the worktable on which the part is mounted. It is more accurate。 the program of instructions is called a part program. . Chapter 1 INTRODUCTION TO NUMERICAL CONTROL Basic Components of NC Machine Tools The program is coded on a suitable medium for submission to the machine control unit. The mon medium in the past is punched tape, magic tape: . Chapter 1 INTRODUCTION TO NUMERICAL CONTROL Basic Components of NC Machine Tools Now, The mon medium is diskette, electronic transfer from a puter(RS232C): . Chapter 1 INTRODUCTION TO NUMERICAL CONTROL Basic Components of NC Machine Tools MCU consists of a microputer and related control hardware that stores the program of instructions and executes it by converting each mand into mechanical actions of machine tool, one mand at a MCU includes system software,calculation algorithm,and transition software to covert the NC parts program into a usable format for the MCU . Chapter 1 INTRODUCTION TO NUMERICAL CONTROL Basic Components of NC Machine Tools Spindle and feed drive motors and their servoamplifiers are the ponents of the servodrive MCU processes the data and generates discrete numerical position mands for each feed drive and velocity mand for the spindle numerical mands are converted into signal voltage by the MCU unit and sent to servoamplifiers, which process and amplify them to the high voltage levels required by the drive
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