数控技术 河南科技大学教案 英文版.docx

1、数控技术 河南科技大学教案 英文版河南科技大学教案首页课程名称 数控技术（双语） 任课教师 韩建海Chapter 2 NC Part Programming 计划学时 8教学目的和要求： By learning the contents of this chapter, students will grasp the basics of NC programming; master the manual programming methods and techniques of NC milling machine, NC lathe, NC machining centers; unders

2、tand the numerical control programming language, process and methods of graphical programming.重点：1. Basic knowledge of CNC programming: programming content and steps, programming methods, NC Machining Process2. Manual programming: G code, M code and other code, hole machining programming, turning pr

3、ogramming, contour milling programming.难点：1. The characteristics and skills ofNC Turning and NC Milling programming.思考题：1. Glossary: NC programming, work coordinates, tool coordinates, part coordinate system, the absolute coordinate system, the relative coordinate system 2. What are the requirements

4、 of ISO standard on the CNC machine tool coordinate system ?3. What are the base points and node points?4. What are the characteristics of NC Turning programming?内容提要This chapter will elaborate the CNC machining process analysis and the typical processing methods; the methods of establishment, struc

5、ture and commonly used algorithms of NC program; and make a brief of the automatic programming.Chapter 2 NC Part Programming2.1 INTRODUCTION The program of instructions is the detailed step-by-step commands that direct the actions of the processing equipmentIn machine tool applications，the program o

6、f instructions is called a part program，and the person who prepares the program is called a part program Numerical control(NC)is a form of automatically operating a machine tool based on coded alphanumeric data. A complete set of coded instructions for executing an operation is called a program. The

7、 program is translated into corresponding electrical signals for input to servo motors that run the machine We call the whole process from part graphics to finishing control medium the programming of numerical control manufacturing, or call it NC Programming .When using numerical control machine too

8、l to manufacture parts，the programming is very importantThe program is not only correct and fast but also effective and economic2.1.1 The Contents and Steps of Numerical Control Programming Before NC programming，the programmer should understand the numerical control machine specifications ,character

9、istics, the functions and programming instruction format of the CNC system，etcWhen programming，he should analyze the parts technical requirements， geometrical shape dimensions and technological requirements. Then he can determine the manufacturing method and calculate numerical value, get cutter pos

10、ition, According to part dimension，cutter position value，cutting parameters(spindle speed，feed-rate，cutting depth) and auxiliary functions(ATC，CW，CCW，coolant on and off)，the programmer can program The program can be inputted into CNC system and the CNC system controls CNC machine tools to manufactur

11、e automatically Generally speaking，the main steps of NC programming are analyzing part graphics，determining the manufacturing technological process, calculating ,numerical value，programming，verifying the program and inputting the program into CNC systemFigure 21 illustrates the programming steps (1)

12、Analyzing part graphics and determining the manufacturing technological process This step includes analyzing the part graphics，understanding the machining contents and requirements，then determining technological processes，machining plans，machining sequence，machining routes，fixing methods，cutting par

13、ameters and selecting cutting tools，etc Besides these，the numerical control machine codes should be understood clearly and the numerical control machine functions should be exploited fully (2)Correctly selecting program origin and coordinate system In numerical control machine tools manufacturing，co

14、rrectly selecting program origin and coordinate system is very importantOn NC programming，the program coordinate system is the standard C00rdlnate system ascertained 0n the workpiece . (3)Calculating numerical values After finishing the technological process，the next step is to get the tool path acc

15、ording to part geometric dimension and the method of cutter radius compensation，SO we will obtain the cutter position (4)Writing part programs After determining machining route，technological process and the coordinate value of tool path，step-by-step，the programmer can write the program in accordance

16、 with the specified function codes and program format of CNC system (5)Fabricating control medium The Program is coded 0n a suitable medium for submission to the machine control unit for many years，the common medium was 1-inch wide Punched tape，using a standard format that could be interpreted by th

17、e machine control unitToday，punched tape has largely been replaced by newer storage technologies in modern shopsThese technologies include magnetic tape，diskette，and electronic transfer of part programs from a computer (6)Verifying part programs Before the program is used in real production，we must

18、check the programWe detect tool path errors that could ruin the part，damage the fixtures，break the cutting tool or crash the machine，etcIn some cases，we test the program through manufacturing a part on a machineOn the basis of detecting result，the program is needed to be modified and to be adjusted

19、until the program satisfies the machining requirements completely The steps above-mentioned are programmed manuallyThis programming method is called manual part programmingAnd we also know that a programmer not only must have the knowledge of the structure of machine tools，the functions and standard

20、s of CNC system， but also have the knowledge of technological process，such as fixtures，cutting tools and cut- ting parameters，etc2.1.2 The Methods of NC Programming Part programming can be accomplished using a variety of procedures ranging from manual method to highly automated method (1)Manual part

21、 programming The programming is called manual part programming which whole part programming is completed manually(including calculating numerical value on a computer) In many mechanical manufacturing trades，there are a large number of uncomplicated parts that are constituted only by the simple geome

22、tric elements of straight lines and circles The numerical values of the parts are calculated simplyThe blocks of a program arent lotAnd checking the program is easyThese part programs can be completed manuallySo manual programming is still a very common programming method at home and abroad But manu

23、al programming has difficulty or impossibility to program complicated parts that have non-circular curves and surfacesSo we must use the automatic part programming to program (2)Automatic programmingAutomatic programming is also called computer-aided Programming. Most or all of the programming is co

24、mpleted by a computer，such as calculating numerical values，writing programs，fabricating the control medium，etcAutomatic programming lightens programmer intensity of labor，shortens the programming time and improves the programming qualityAt the same time，it solves the complicated part programming whi

25、ch is impossible to program by manual programmingThe more parts are complicated shape and technological process，the more superiority of automatic programming clear is There are many methods of automatic part programmingAccording to the differences of input programming message and handling styles by

26、a computer，they are divided into automatically programmed tool(APT)based on automatic programming language and part programming using CAD/CAM(computer-aided design/computer aided manufacturing)based on interactive graphics systemA CAD/CAM system is a computer interactive graphics sys- tem equipped w

27、ith software to accomplish certain tasks in design and manufacturing. 2.1.3 The Basis of NC Part Programming2.1.3.1 The Geometric Basis of NC Part Programming (1)NC Coordinate systems The location of a CNC Machine tools at any time is controlled by a system of XYZ coordinates called Cartesian coordi

28、natesThis system is composed of three directional lines，called axes，mutually intersecting at an angle of 90The point of intersection is known as the originThose axis system standards include： (i)Primary machine axes of movement：should follow the right-hand rule. See Figure 2.2. (ii)Spindle movement

29、is primarily along the Z ax- isMovement into the workpiece is along the-Z axis and movement away from the workpiece is along the +Z axis (iii)In a majority of milling machines，motion along the X axis is the longest travel perpendicular to ZThe X axis is parallel to the work holding and is in the hor

30、izontal planeThe +X axis moves to the right along a plane Othe work as the operator looks at that plane (iv)With regard to milling machines，motion along the Y axis is the shortest travel perpendicular to ZThe Y axis is in the same plane as the X axisLooking at the plane，the operator will note that t

31、he Y axis is perpendicular to the X axis Most CNC milling machines can perform simultaneous motions along the X，Y，and Z axes and are called three-axis machinesSee Figures 23 and Figure 24 More complex CNC machines have the capability of executing additional rotary motions as follows：Rotation about a

32、n axis parallel to the X axis or A-axis rotationRotation about an axis parallel to the Y axis or B-axis rotationRotation about an axis parallel to the Z axis or C-axis rotationRotary motion directions also follow the right-hand ruleSee Figure 25 and Figure 26 (2)Program zero point The programming zero point is rela