【正文】 ot welding and continuous arc welding machines are available with automatic controls based on NC. . Chapter 1 INTRODUCTION TO NUMERICAL CONTROL Application of CNC NonMachine Tool Application Thermal cutting machine (數(shù)控熱切割機 ) Such as oxyfuel cutting(火焰切割 ),laser cutting(激光切割 ), and plasma arc cutting(等離子電弧切割 ). The stock is usually flat。 （連續(xù)控制或 輪廓 控制系統(tǒng)） . Chapter 1 INTRODUCTION TO NUMERICAL CONTROL Types of NC Motion Control System Pointtopoint control system Point –to point (positioning) control in NC It is also called Positioning control system, Which moves the worktable to a programmed location without regard to the path taken to get to the location. That is to say ,the path between points is of little concern and is not particularly controlled. The program consists of a series of point locations at which operations are performed. Such as drilling or punching a hole. . Chapter 1 INTRODUCTION TO NUMERICAL CONTROL Types of NC Motion Control System pointtopoint control system Many NC point –topoint systems contain a more plex MCU. IN these servos, positioning mands are evaluated simultaneously so that vector motion in two axes is possible. The movements between points can be done along straight or 450 vectors paths determined by the machine ways or slides. Such systems are some times called straightcut control system.（點位 /直線） . Chapter 1 INTRODUCTION TO NUMERICAL CONTROL Types of NC Motion Control System Contouring Control System It is also called continuous path control system, which manages the simultaneous motion (resultant motion)of the cutting tool in two, three, four, of five axes by interpolating(插補 )the proper path between prescribed points. It enables the cutting 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