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1、机电专业英语教案模块1Module 1 Foundation of Mechanical Technology学习任务1Task 1 Mechanical EngineeringTeaching contentRemarksText1.1.1. Drawing1. Engineering drawing Typical drawings in machine manufacturing are classified as part drawings and assembly drawings.在机械制造中比较典型的机械图样有两种：零件图和装配图。Fig.1-1-1 Part drawingsF
2、ig.1-1-2 Assembly drawings2. Representation of machine elementsMechanical drawings in national standards are restricted to those which specify the view, sectional view and broken sectional view to represent the structures and shapes.国家机械制图标准规定采用视图、剖视图、断面图等各种方法来表达机件的结构和形状。Basic viewsSectional views B
3、roken sectional views1.1.2 Properties of Metals1. MetalsMetals are divided into two general groups: ferrous metals and nonferrous metals. The major types of ferrous metals are iron, carbon steels, alloy steels and tool steels.金属材料分为两种基本类型：铁类金属和非铁金属。铁类金属主要有铸铁、碳钢、合金钢和工具钢。The three primary types of cas
4、t iron are gray cast iron, white cast iron, and malleable iron.铸铁主要分为三种：灰铸铁、白口铸铁和可锻铸铁。 The three principal types of carbon steel used in industry are low, medium, and high carbon steel.工业上使用的碳钢主要有三种：低碳钢、中碳钢和高碳钢。2. Properties of metals Strength is a property of metal that allows it to resist permanen
5、t change in shape when loads are applied. 强度是材料在载荷作用下抵抗塑性变形的能力。 Hardness is the ability of a metal to resist indentation or penetration. 硬度是材料抵抗压痕或划痕的能力。 Wear resistance is the ability of a metal to resist abrasion. 耐磨性是材料抵抗磨损的能力。 Toughness is the ability of a metal to resist, or absorb, sudden shoc
6、ks of loads without breaking.韧性是材料抵抗或吸收或冲击载荷而不发生破坏的能力。Plasticity is the ability of a metal to be extensively deformed without fracture or rupture.塑性是材料产生塑性变形而不被破坏的能力。Brittleness is the property of a metal that causes it to fracture rather than deform when loads are applied.脆性是指材料在载荷作用下不产生明显变形而直接发生破坏
7、的特性。1.1.3 Heat Treatment of MetalsFig.1-1-6 Heat treatment curvePurposes of annealing: remove hardness; increase malleability; increase ductility; improve machine-ability; refine grain structure.退火的目的：降低硬度；提高可锻性；提高延展性；改善机械加工性能；改善组织。Purposes of normalizing: relieve stresses; produce normal grain size
8、 and structure; place steels in the best condition for machining; lessen distortion in heat treating.正火的目的：消除应力；细化晶粒和改善结构均匀性；为机械加工做准备；减少热处理产生的变形。Purposes of hardening: increase hardness, strength and wear resistance.淬火的目的：提高硬度、强度和耐磨性。Purposes of tempering: reduce hardness to desired level; increase
9、shock resistance and impact strength; reduce brittleness; relieve stresses caused by rapid cooling.回火的目的：降低硬度到所需要的水平；提高抗冲击性和冲击强度；降低脆性；消除快速冷却产生的内应力。1.1.4 Machine Elements1. Machine and partsHowever simply, any machine is a combination of individual components generally referred to as machine elements
10、 or parts.无论多么简单的机器，都是由单一构件即通称的机械零件或部件组成的。2. Name of different gear partsFig.1-1-7 Name of different gear parts3. Gear types and applicationsThere are several kinds of gears used in modem machinery. Some of those are spurs, helical, gear racks, bevel, worm and worm wheel.在现代机械中使用的齿轮有很多种，其中有直齿圆柱齿轮、斜齿
11、轮、齿条、锥齿轮、蜗轮蜗杆等。 Fig.1-1-8 Spur gears Fig.1-1-9 Helical gear Fig.1-1-10 Bevel gearsExercises. Match A with B A B耐磨性 assembly drawings正火 sectional views灰铸铁 gray cast iron剖视图 tensile strength抗拉强度 wear resistance齿根圆 normalizing装配图 dedendum circle. Mark the following statements with T (true) or F (false)
12、 ( ) 1. Directional views include full sectional views, half sectional views and partial sectional views.( ) 2. The axonometric drawing is used for complementing the outline of the body.( ) 3. Metals are divided into three general groups: gray cast iron, white cast iron, and malleable iron.( ) 4. Br
13、ittleness is the opposite of plasticity.( ) 5. Tempering relieves some of the stressed caused by rapid cooling in the hardening process.( ) 6. The addendum circle of the external gear is smaller than its dedendum circle. Answer the following questions briefly according to the text. 1. Which two kind
14、s are typical drawings in machine manufacturing divided into?2. What is the application of malleable cast iron?3. What is the carbon content of medium carbon steel?4. Whats definition of the strength?5. What is the function of the normalizing?Reading MaterialAnnealing TypesThere three types of annea
15、ling processes used in industry are full annealing, process annealing, and spheroidizing.工业中应用的退火主要有三种：完全退火、低温退火和球化退火。Full annealing is used to produce maximum softness in steel. Machinability is improved. Internal stresses are relieved.完全退火用来最大限度的降低钢的硬度，以改善他的切削加工性能，消除内应力。Process annealing is also c
16、alled stress relieving. It is used for relieving internal stresses that have occurred during cold-working or machining processes. 低温退火也称去应力退火，他的目的主要就是消除在冷加工和机械加工过程中产生的内应力。Spheroidizing is used to produce a special kind of grain structure that is relatively soft and machine-able. This processes gener
17、ally used to improve the machine-ability.球化退火是使钢中生成一种特殊的晶粒结构，这种结构相对较软而易于加工。这种工艺一般用于改善高碳钢的切削加工性能。掌握机械图样分类及组成重点零件图的表达方式此部分结合机械制图课程进行动导向教学法结合金属材料课程讲解与提问交叉进行难点：三种铸铁、三种钢的异同讨论教学法对比法讲解结合机械设计基础该部分内容采用启发式方式授课模块1Module 1 Foundation of Mechanical Technology学习任务3Task 3 CNC ProgramTeaching contentRemarksText1.3.
18、1 Basic CNC Program1. Coordinate SystemsThe machine manufacturer sets a machine zero point for each machine. The machine zero point is the origin of the machine coordinate system. When the operator wants to determine the position of the workpiece on the machine, he must set the workpiece coordinate
19、systems. If the dimension of a workpiece is too big, the user can set another coordinate system in a local area of the workpiece, this is a local coordinate system.机床制造商为每一台机床设置一个机床零点，机床零点是机床坐标系的原点。操作者编程时需要确定零件在机床上的位置时，必须建立工件坐标系。当工件尺寸太大时，用户可以在工件上的某一局部区域设定另一个坐标系，这个坐标系就是局部坐标系。The coordinates in a coor
20、dinate system represent the tool position. Coordinates axes （Fig.1-3-2）are used to specify the coordinates.坐标系中的坐标代表刀具的位置，坐标轴(图1-3-2)用来确定坐标。2. Program ZeroThe origin point for each axis is commonly called the program zero point, also called work zero, part origin or zero point.每个坐标轴的原点通常称为程序零点，也称为工件
21、零点，工件原点或零点。3.Absolute VS. Incremental Coordinate（Fig.1-3-4）If the tool moves to a target point, the coordinate value of it is determined on the basis of zero point of the workpiece coordinate system. This value is the absolute coordinate value. If the tool moves from the present point to a target po
22、int, the coordinate value of the target point is determined on the basis of the previous tools coordinate value. This value is the increment coordinate value.如果刀具移动到某一个目标点，该点的坐标值是以工件坐标系的原点为基准而确定的，此值即为该位置的绝对坐标值。如果刀具从当前点移动到某一个目标点，该目标点的坐标值是相对于刀具前一个位置坐标来计算的，此值即为该位置的增量坐标值。4.The G , F , S , M and T CodesG
23、-codes are also called preparatory codes or words. A preparatory function is designated by the address G followed by one or two digits to specify the mode in which a CNC machine moves along its programmed axes.G代码通常分为两类。模态G代码在随后的程序段一直有效，直至被同组的另一个代码代替。非模态G代码功能仅在所出现的程序段内起作用。The F-code （Fig.1-3-5）contr
24、ols the speed of the cutting feed.F代码（图1-3-5）控制切削进给速度。The S- code （Fig.1-3-6）controls the spindle speed. The selected speed value right follows the S address.S代码（图1-3-6）控制主轴转速。S地址后面是所选择的转速值。M-codes are called the miscellaneous words and are used to control miscellaneous function of the machine.M代码被叫
25、做辅助功能字，控制机床的辅助功能。T-code（Fig.1-3-7） is used to specify the tool number. It is used only for an automatic tool changer machine.T代码（图1-3-7）被用来指定刀具号。用于有自动换刀装置的机床。1.3.2 Manual Program Code1. Basic Program Codes(1)G00 (rapid positioning)The G00 command moves a tool to the position in the workpiece system
26、specified with an absolute or an incremental command at a rapid traverse rate.G00指令是在工件坐标系中以快速移动速度移动刀具到达由绝对或增量指令指定的位置。The G01 command moves a tool along a line to the specified position at the feed rate specified in F code.G01指令是将刀具以代码指定的进给速度沿直线移动到指定的位置。G02/G03 (circular interpolation) command will
27、move a tool along a circular arc. The arc center is specified by addresses I, J and K for the X , Y and Z axes, respectively.G02/G03 （圆弧插补）指令使刀具沿圆弧运动。圆弧圆心是用地址I、J和K（分别对应于X , Y 和 Z轴的坐标）指定的。2. Tool Compensation Codes(1)Tool length compensation（Fig.1-3-8）Tool length compensation(2)Tool radius compensati
28、on （Fig.1-3-9）G41与 G423. Multiple Repetitive Cycle CodesG71 (stock removal in turning) canned cycle will rough out material on a part given the finished part shape. All that a programmer needs to do is define the shape of a part by programming the finished tool path and then submitting the path defi
29、nition to G71 by means of a PQ block designation.G71循环指令能按照给定的精加工后零件形状粗车去除多余材料。通过编程精加工刀具轨迹来定义零件形状，并且通过PQ程序段指定把刀具轨迹赋予G71指令。G73 (pattern repeating in turning) canned cycle permits cutting a fixed pattern repeatedly, with a pattern being displaced bit by bit.G73 (仿型粗车循环)指令可以车削固定的图形，并且是按此图形逐步逼近。通过这种切削循环
30、，就可以高效的切削已粗车成型、铸造成型或锻造成型的工件。G81 (drilling cycle)Rapidly move to the X and Y coordinate of the hole position.Rapidly move to Z axis reference plane (R).Feed to the Z axis final depth. Rapidly back to either the Z axis initial position or the Z axis reference plane (R).X轴和Y轴快速定位到孔中心的位置上。快速运行到Z向参考平面。Z向
31、切削进给到最终深度。快速退回到Z向初始位置或Z向参考平面。4. SubprogramIf a program contains a fixed sequence or frequently repeated pattern, such a sequence or pattern can be stored as a subprogram in memory to simplify the program.一个程序包含固定顺序或频繁重复的图形，这样的顺序或图形就可以编成子程序存在存储器中以简化编程。1.3.3 Automatic Programming1. Create the geometry
32、 modeling (1) By using the graphical design interface provided by MasterCAM X.（1）使用MasterCAM X提供的交互绘图设计。 (2) By making the design in CAD software, e.g. UG, Pro/E, SolidWorks then saving it in a format that MasterCAM X can import.（2）在CAD软件比如UG, Pro/E, SolidWorks中进行设计，然后保存成MasterCAM X能导入的格式。2. Creatin
33、g the tool path(1) Select the machine type（Fig.1-3-13）(2) Look for an existing tool that you may want to use （Fig.1-3-14, Fig.1-3-15）(3) Create the tool path（Fig.1-3-16）3. Verify the cutting process（Fig.1-3-17, Fig.1-3-18） Before a part is machined, the CAM model needs to be verified that the part p
34、rogram is correct. 在一个零件加工之前，需要验证CAM模型的零件程序是否正确。4. Create the G codes （Fig.1-3-19） Different CNC machines use slightly different versions of G codes. The conversion of the machining data to the G codes specific for a particular CNC machine is called post-processing. The format of the G code is store
35、d in different post-processing files and the system will use whichever post-processing format you select. 不同的数控机床所使用的G代码形式有一定的区别。将加工的数据转换成某一机床所需的G代码格式称为后处理。G代码被存储成不同格式的后处理文件，可以根据需要选择后处理文件格式。Exercises. Match A with B A B仿型粗车循环 incremental coordinate增量坐标 subprogram几何模型 tool compensation刀具补偿 pattern re
36、peating in turning子程序 drilling cycle钻孔循环 geometry modeling. Mark the following statements with T (true) or F (false) ( ) 1. The operator sets a machine zero point for each machine.( ) 2. A positive motion in the Z direction moves the cutting tool away from the workpiece. ( ) 3. Generally speaking, t
37、here are three types of program: the program number, the program content and the program end.( ) 4. Many controls use a D word to specify the offset number used with tool radius compensation.( ) 5. A single call program code (M98) can only call a subprogram once.( )6. In MasterCAM you cant see the G
38、 codes file. Answer the following questions briefly according to the text. 1. Who determines the program zero?2. What does the program number usually start with?3. Which command moves a tool to the position in the workpiece system specified with an absolute or an incremental command at a rapid trave
39、rse rates.4. When had we better use subprogram?Reading MaterialProgram ConfigurationGenerally speaking, there are two types of program: the main program and the subprogram. The main program contains a series of commands for machining workpieces. The subprogram can be called by the main program or an
40、other subprogram. Either the main program or a subprogram contains three parts: the program number, the program content and the program end. 一般来说，程序类型有两种：主程序和子程序。主程序包括一系列加工工件的指令。子程序可以被主程序或另外一个子程序调用。不论是主程序还是子程序都由三部分组成：程序号、程序内容、程序结束。 A CNC program consists of one or more blocks of commands. A block is
41、 a complete line of information to the CNC machine. It consists of one word or an arrangement of words. Blocks may vary in length. 一个数控程序包含一个或多个程序段。一个程序段是包含机床信息的一个完整行。它包含一个或一系列的字，程序段的长度可以变化。对比法教授手势演示结合编程教学教学难点联系编程知识授课对比法、启发式结合授课看图学习看图学习联系编程教学，启发学生讲授看图讲授结合软件教学讲授以学生练习为主，提示、引导为辅分层教学使用模块1Module 1 Founda
42、tion of Mechanical Technology学习任务4Task 4 Tolerance and MeasureTeaching contentRemarksText1.4.1 Tolerance The nominal size of a component dimension is arrived at as a convenient size based on the design process. 零件的公称尺寸是设计人员根据设计工艺的需要而制定的一个恰当的尺寸值。 It is therefore customary in engineering practice to a
43、llow a permissible deviation from the nominal size, which is termed as tolerance. Tolerance on a dimension can also specify the degree of accuracy. 在工程实际中常允许在公称尺寸左右有一个变化范围，这称为公差。尺寸的公差也能说明尺寸的精确程度。 Take for example a shaft and hole, which will have to fit together. In the simplest case if the dimension of the shaft is lower than the dimension of the hole, then there will be clearance. Such a fit is termed clearance fit. Alternatively, if the dimension of the shaft is more than that of the hole, then it is termed interfere