数控技术中英文教学概述

1、 . chapter 1 introduction to numerical control 1.1、fundamental of nc technology 1.2、classifications of nc machines 1.3、features of numerical control and its application areas . chapter 1 introduction to numerical control 1.1.1、development history of nc 1946-the first computer appeared in the world,

2、which lift the curtain on the mankind into information time. 1948-parsons corporation brought forward using computer to control machine when they machined the surface contours of airfoil shape. parsons corporation was a mini-helicopter manufacturer. the machining accuracy of the airfoil shape was 0.

3、0381mm . chapter 1 introduction to numerical control 1.1.1、development history of nc under the support by the u.s air force responsed by the servomechanisms laboratory at the mit (massachusetts institute of technology) . chapter 1 introduction to numerical control 1.1.1、development history of nc thr

4、ee years later, in 1952 mit and parsons corporation cooperated with each other, and developed the first nc machine which named cincinnati hydrotel milling machine. background, time and place . chapter 1 introduction to numerical control 1.1.1、development history of nc the first generation,19521955 v

5、acuum tubes, electrical relays and complicated machine control interfaces. the second generation,19551959 miniature electronic tubes, transistors. the third generation,19591965 small scale integrated circuits. . chapter 1 introduction to numerical control 1.1.1、development history of nc above three

6、generations, their nc functions were performed by hardware(electronic circuits), so we call them“hardwired nc”(硬线数控硬线数控) 1955 1959 1965 . chapter 1 introduction to numerical control 1.1.1、development history of nc the fourth generation,1970s (19701974)minicomputers. (cnc) the fifth generation,1974-

7、microprocessor.1979(vlic) (mcnc) 1994 pc-nc. . chapter 1 introduction to numerical control 1.1.1、development history of nc after the fourth generations, their nc functions were performed by software(based on computer), so we call them“softwired nc” or “computer numerical control”(计算计算 机数控机数控cnc) 197

8、0 1974 1994 . chapter 1 introduction to numerical control 1.1.2 concept of nc and cnc 1、nc (numerical control,数字控制数字控制) numerical control（nc）is a form of programmable automation in which the mechanical actions of a machine tool or other machines are controlled by a program containing coded alphanume

9、ric data. . chapter 1 introduction to numerical control 1.1.2 concept of nc and cnc 2、numerical control technology, (数控技术数控技术) it means the technology which adopts nc methods to control a work process to realize the automation. . chapter 1 introduction to numerical control 1.1.2 concept of nc and cn

10、c 3、numerical control machine tools, (数控机床数控机床) it is a kind of machine tools which adopts the numerical control technology to realize the work process automation. it is a typical example of nc application. . chapter 1 introduction to numerical control 1.1.2 concept of nc and cnc 4、numerical control

11、 system, (数控系统数控系统) it is the equipment which can realize the numerical control. . chapter 1 introduction to numerical control 1.1.2 concept of nc and cnc 5、cnc(computer numerical control, 计算机数控计算机数控) the machine control units are based on computer technology. . chapter 1 introduction to numerical c

12、ontrol 1.1.3 basic components of nc machine tools the control system of a numerically controlled machine tool can handle many tasks commonly done by the operator of a conventional machine. the system has the ability to perform the control functions through the numerical input information, which is t

13、he control program, also called the part program. . chapter 1 introduction to numerical control 1.1.3 basic components of nc machine tools the work process of nc is shown as the right figure. part drawing part program control computer servo-drive unit machine tool part firstly, the part programmer s

14、hould study the part drawing and the process chart. . chapter 1 introduction to numerical control 1.1.3 basic components of nc machine tools the work process of nc is shown in the right figure. part drawing part program control computer servo-drive unit machine tool part then the part programmer sho

15、uld prepare the control program on a standard form in the specified format. it contains all the necessary control information . chapter 1 introduction to numerical control 1.1.3 basic components of nc machine tools the work process of nc is shown in the right figure. part drawing part program contro

16、l computer servo-drive unit machine tool part next the part program is transferred into the control computer(mdi).the computer converts each command into the signal that the servo-drive unit needs . chapter 1 introduction to numerical control 1.1.3 basic components of nc machine tools the work proce

17、ss of nc is shown in the right figure. part drawing part program control computer servo-drive unit machine tool part at last , the servo- drive unit drives the machine tool to manufacture the finished part . chapter 1 introduction to numerical control 1.1.3 basic components of nc machine tools a typ

18、ical nc machine tool has five fundamental units: (1)the input media; (2)the machine control unit; (3)the servo-drive unit; (4)the feedback transducer; (5)the mechanical machine tool unit . chapter 1 introduction to numerical control 1.1.3 basic components of nc machine tools the general relationship

19、 among the five components is illustrated in the below. machine control unit input mediaservo- drivemachine tool feedback transducer . chapter 1 introduction to numerical control 1.1.3 basic components of nc machine tools machine control unit input mediaservo- drivemachine tool feedback transducer t

20、he input media contains the program of instructions, it is the detailed step-by-step commands that direct the actions of the machine tool; the program of instructions is called a part program. . chapter 1 introduction to numerical control 1.1.3 basic components of nc machine tools machine control un

21、it input mediaservo- drivemachine tool feedback transducer the program is coded on a suitable medium for submission to the machine control unit. the common medium in the past is punched tape, magnetic tape: . chapter 1 introduction to numerical control 1.1.3 basic components of nc machine tools mach

22、ine control unit input mediaservo- drivemachine tool feedback transducer now, the common medium is diskette, electronic transfer from a computer(rs232c): . chapter 1 introduction to numerical control 1.1.3 basic components of nc machine tools machine control unit input mediaservo- drivemachine tool

23、feedback transducer mcu consists of a microcomputer and related control hardware that stores the program of instructions and executes it by converting each command into mechanical actions of machine tool, one command at a time.the mcu includes system software,calculation algorithm,and transition sof

24、tware to covert the nc parts program into a usable format for the mcu . chapter 1 introduction to numerical control 1.1.3 basic components of nc machine tools machine control unit input mediaservo- drivemachine tool feedback transducer spindle and feed drive motors and their servo-amplifiers are the

25、 components of the servo-drive unit.the mcu processes the data and generates discrete numerical position commands for each feed drive and velocity command for the spindle drive.the numerical commands are converted into signal voltage by the mcu unit and sent to servo-amplifiers, which process and am

26、plify them to the high voltage levels required by the drive motors. the drives in machine tools are classified as spindle and feed drive mechanisms. . chapter 1 introduction to numerical control 1.2 classifications of nc machine numerical control machines are classified in different way: (1)the type

27、s of nc motion control system; (2)the type of servo-drive system; (3)application of nc . chapter 1 introduction to numerical control 1.2.1 types of nc motion control system motion control systems for nc can be divided into two types: (1) point-to-point control system (点位控制系统点位控制系统); (2) continuous (

28、contouring)path control system; （连续控制或（连续控制或轮廓轮廓控制系统）控制系统） . chapter 1 introduction to numerical control 1.2.1 types of nc motion control system 1.2.1.1 point-to-point control system point to point (positioning) control in nc it is also called positioning control system, which moves the worktable to

29、 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.

30、 . chapter 1 introduction to numerical control 1.2.1 types of nc motion control system 1.2.1.1 point-to-point control system many nc point to-point systems contain a more complex mcu. in these servos, positioning commands are evaluated simultaneously so that vector motion in two axes is possible. th

31、e 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 straight-cut control system.（点位（点位/直线）直线） . chapter 1 introduction to numerical control 1.2.1 types of nc motion control system 1.2.1.2 contouring c

32、ontrol 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(插补插补)the proper path between prescribed points. it enables the cutting tool to generate angular surfaces, two

33、-dimensional curves, or three-dimensional contours in the workpiece, such as milling and turning operations. . chapter 1 introduction to numerical control 1.2.1 types of nc motion control system 1.2.1.3 interpolation to cut along a circular path,the circle must be divided into a series of straight-l

34、ine segments that approximate the circular path.the tool is commanded to machine each line segment in succession so that the machined surface closely matches the desired shape. . chapter 1 introduction to numerical control 1.2.2 types of nc servo-drive system the principal function of nc is the posi

35、tioning 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 accomplishes positioning. these are the open- loop（开环）（开环）, the closed-loop（闭环）（闭环） and half closed-loop（半闭环）（半闭环） drive system. . chapte

36、r 1 introduction to numerical control 1.2.2 types of nc servo-drive system 1.2.2.1 open-loop servo-drive it is the simplest and least cost form of servo-drive. 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

37、 the action of the control signal. driving circuit stepping motor worktable leadscrew pulse train . chapter 1 introduction to numerical control 1.2.2 types of nc servo-drive system 1.2.2.2 half-closed-loop servo-drive it is characterized as a system that the indirect feedback monitors the output of

38、servomotor.although this method is popular with nc systems, it is not as accurate as direct feedback, the half-closed-loop system compares the command position signal with the drive signal of the servomotor. . chapter 1 introduction to numerical control 1.2.2 types of nc servo-drive system 1.2.2.2 h

39、alf-closed-loop servo-drive position compare circuit speed control circuit worktable instruction speed feedback signal position feedback signal leadscrew servomotor . chapter 1 introduction to numerical control 1.2.2 types of nc servo-drive system 1.2.2.3 closed-loop servo-drive it is characterized

40、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.

41、it is more accurate; however, its implementation costs are higher. . chapter 1 introduction to numerical control 1.2.2 types of nc servo-drive system 1.2.2.3 closed-loop servo-drive position compare circuit speed control circuit worktable instruction speed feedback signal position feedback signal le

42、adscrew servomotor . chapter 1 introduction to numerical control 1.2.3 application of cnc the applications of cnc are divided into two categories: (1)machine tool applications; (2) non-machine tool applications. it should be noted that the applications are not always identified by the name “numerica

43、l control”, this term is used principally in the machine tool industry. . chapter 1 introduction to numerical control 1.2.3 application of cnc 1.2.3.1 machine tool application the most common applications of nc are in machine tool control, machining was the first application of nc . machining is a m

44、anufacturing process in which the geometry of work is produced by removing excess material. by controlling the relative motion between a cutting tool and the workpiece, the desired geometry is created. . chapter 1 introduction to numerical control 1.2.3 application of cnc 1.2.3.1 machine tool applic

45、ation the common nc machine tools are listed in the following along with their typical features: nc lathe (数控车床数控车床) turning requires two-axis continuous path control, either to produce a straight cylindrical geometry or to create a profile. . chapter 1 introduction to numerical control 1.2.3 applic

46、ation of cnc 1.2.3.1 machine tool application nc boring mill (数控镗铣床数控镗铣床) horizontal or vertical spindle. boring is similar to turning, except that an internal cylinder is created instead of an external cylinder. the operation requires continuous path, two-axis control. . chapter 1 introduction to n

47、umerical control 1.2.3 application of cnc 1.2.3.1 machine tool application nc drill press (数控钻床数控钻床) these machines use point- to-point control of workhead and two axis control of the worktable. some nc drill presses have turrets containing six or eight drill bits. . chapter 1 introduction to numeri

48、cal control 1.2.3 application of cnc 1.2.3.1 machine tool application nc milling machine (数控铣床数控铣床) it requires continuous path control to perform straight cut or contouring operations. . chapter 1 introduction to numerical control 1.2.3 application of cnc 1.2.3.1 machine tool application nc grindin

49、g machine (数控磨床数控磨床) it is intended for finishing treatment of workparts. the grinding machine includes cylindrical-, surface-, internal-, spindle-,thread- ,gear-and tool- grinding machines. . chapter 1 introduction to numerical control 1.2.3 application of cnc 1.2.3.1 machine tool application machi

50、ne center (加工中心加工中心) it is defined as multifunction nc machines with automatic tool changer and tool storage.it has the ability to perform drilling, turning, reaming, boring, milling, contouring, and threading operations on a single machine. . chapter 1 introduction to numerical control 1.2.3 applic

51、ation of cnc 1.2.3.1 machine tool application machine center (加工中心加工中心) machining centers are classified as either vertical or horizontal. vertical machining centers continue to be widely accepted and used, primarily for flat parts and where three-axis machining is required on the surface of a singl

52、e part such as the mold and the die. horizontal machining centers are particularly used for the large,boxy, and heavy parts. . chapter 1 introduction to numerical control 1.2.3 application of cnc 1.2.3.1 machine tool application machine center (加工中心加工中心) . chapter 1 introduction to numerical control

53、 1.2.3 application of cnc 1.2.3.2 non-machine tool application punch presses for sheet metal hole punching (数控冲床数控冲床) the two-axis nc operation is similar to that of a drill press except that holes are produced by punching rather than by drilling. . chapter 1 introduction to numerical control 1.2.3

54、application of cnc 1.2.3.2 non-machine tool application presses for sheet metal bending (数控折弯机数控折弯机) instead of cutting sheet metal, these systems bend sheet metal according to programmed commands. . chapter 1 introduction to numerical control 1.2.3 application of cnc 1.2.3.2 non-machine tool applic

55、ation welding machine (数控焊接机数控焊接机) both spot welding and continuous arc welding machines are available with automatic controls based on nc. . chapter 1 introduction to numerical control 1.2.3 application of cnc 1.2.3.2 non-machine tool application thermal cutting machine (数控热切割机数控热切割机) such as oxyfuel cutting(火火 焰切割焰切割),laser cutting(激光切激光切 割割), and plasma arc cutting(等等 离子电弧切割离子电弧切割). the stock is usua