機電-體化專業(yè)英語Unit 3

1、Machining Operations and Turning MachinesPart I Technical and Practical Reading Passage A Machining Operations Conventional machining, one of the most important material removal methods, is a collection of material-working processes in which power-driven machine tools, such as lathes, milling machin

2、es, and drill presses are used with a sharp cutting tool to mechanically cut the material to achieve the desired geometry. Machining is a part of the manufacture of almost all metal products. It is not uncommon for other materials to be machined. A person who specializes in machining is called a mac

3、hinist. Machining is also a hobby. A room, building, or company where machining is done is called a machine shop. Much of modern day machining is controlled by computers using Computer Numerical Controlled (CNC) machining. Machining operations The three principal machining processes are classified a

4、s turning, drilling and milling. Other operations falling into miscellaneous categories include shaping, planning, boring, broaching and sawing. Turning operations are operations that rotate the work-piece as the primary method of moving metal against the cutting tool. Lathes are the principal machi

5、ne tool used in turning. Milling operations are operations in which the cutting tool rotates to bring cutting edges to bear against the work-piece. Milling machines are the principal machine tool used in milling. Drilling operations are operations in which holes are produced or refined by bringing a

6、 rotating cutter with cutting edges at the lower extremity into contact with the work-piece. Drilling operations are done primarily in drill presses but not uncommonly on lathes or mills. More recent, advanced machining techniques include electrical discharge machining (EDM), electro-chemical erosio

7、n, laser, or water jet cutting to shape metal work-pieces. Machining requires attention to many details for a work-piece to meet the specifications set out in the engineering drawings or blueprints. Types of machining operation There are many kinds of machining operations, each of which is capable o

8、f generating a certain part geometry and surface texture. In turning, a cutting tool with a single cutting edge is used to remove material from a rotating work-piece to generate a cylindrical shape. The speed motion in turning is provided by the rotating work-part, and the feed motion is achieved by

9、 the cutting tool moving slowly in a direction parallel to the axis of rotation of the work-piece. Drilling is used to create a round hole. It is accomplished by a rotating tool that is typically has two cutting edges. The tool is fed in a direction parallel to its axis of rotation into the work-par

10、t to form the round hole. In boring, the tool is used to enlarge an already available hole. It is a fine finishing operation used in the final stages of product manufacture.In milling, a rotating tool with multiple cutting edges is moved slowly relative to the material to generate a plane or straigh

11、t surface. The direction of the feed motion is perpendicular to the tools axis of rotation. The speed motion is provided by the rotating milling cutter. Overview of machining technology Machining is not just one process; it is a group of processes. The common feature is the use of a cutting tool to

12、form a chip that is removed from the work-part, called swarf . To perform the operation, relative motion is required between the tool and work. This relative motion is achieved in most machining operation by means of a primary motion, called cutting speed and a secondary motion called feed. The shap

13、e of the tool and its penetration into the work surface, combined with these motions, produce the desired shape of the resulting work surface. Notes 1. Conventional machining, one of the most important material removal methods, is a collection of material-working processes in which power-driven mach

14、ine tools, such as lathes, milling machines, and drill presses are used with a sharp cutting tool to mechanically cut the material to achieve the desired geometry. 在這個長句中，主語是Conventional machining，謂語動詞為is。one of the mostmethods是插入語。in which 引導定語從句，其先行詞為processes。在定語從句中，are used是定語從句中的謂語動詞。此句可譯為：常規(guī)加工

15、是集材料加工過程于一體的最重要的切削材料方法之一，在此過程中電動機床，如車床、銑床和鉆床通過鋒利的刀具被用來進行機械加工以獲得期望的幾何形狀。2. Drilling operations are operations in which holes are produced or refined by bringing a rotating cutter with cutting edges at the lower extremity into contact with the work-piece. 在此句中，in which 引導定語從句，修飾先行詞operations。by表示方法、方式

16、。bring with 表示帶有。into contact with 意為“與接觸”。本句可譯為：鉆削操作是通過帶有刀刃的旋轉(zhuǎn)刀具對工件進行深加工孔或深精加工孔的操作。3. The shape of the tool and its penetration into the work surface, combined with these motions, produce the desired shape of the resulting work surface. 在此句中，主語是由and連接的并列主語，謂語動詞為bined with是分詞作狀語。整句意思為：刀具的

17、形狀、刀具與工件面的劃入接觸加上它們之間的運動生成了最終的工件面。 1. The principal machining processes are generally regarded as three parts: turning, drilling and boring.2. Milling machines are the principal machine tool which is used in turning.3. Drilling is a kind of method to create a round hole.4. The purpose of a tool used

18、is to enlarge an available hole in boring.5. Machining is not only one process, but also a group of processes. EXERCISE 1 Mark the following statements with T (True) or F (False) according to the passage. (F)(F)(T)(T)(F)1. conventional machining _2. _ 銑床3. numerical control _4. _ 放電5. chemical erosi

19、on _6. _ 工程圖7. surface texture _8. _ 進給運動 EXERCISE 2Translate the following phrases into Chinese or English. 常規(guī)加工milling machines數(shù)控electrical discharge化學腐蝕engineering drawings表面紋理feed motionPassage B Turning Machines Turning machines, typically referred to as lathes, can be found in a variety of siz

20、es and designs. While most lathes are horizontal turning machines, vertical machines are sometimes used, typically for large diameter work-pieces. Turning machines can also be classified by the type of control that is offered. A manual lathe requires the operator to control the motion of the cutting

21、 tool during the turning operation. Turning machines are also able to be computer controlled, in which case they are referred to as a computer numerical control (CNC) lathe. CNC lathes rotate thework-piece and move the cutting tool based on commands that are preprogrammed and offer very high precisi

22、on. In this variety of turning machines, the main components that enable the work-piece to be rotated and the cutting tool to be fed into the work-piece remain the same. These components include the followingBed The bed of the turning machine is simply a large base that sits on the ground or a table

23、 and supports the other components of the machine. Headstock assembly The headstock assembly is the front section of the machine that is attached to the bed. This assembly contains the motor and drive system which powers the spindle. The spindle supports and rotates the work-piece, which is secured

24、in a work-piece holder or fixture, such as a chuck or collet. Tailstock assembly The tailstock assembly is the rear section of the machine that is attached to the bed. The purpose of this assembly is to support the other end of the work-piece and allow it to rotate, as its driven by the spindle. For

25、 some turning operations, the work-piece is not supported by the tailstock so that material can be removed from the end. Carriage The carriage is a platform that slides alongside the work-piece, allowing the cutting tool to cut away material as it moves. The carriage rests on tracks that lay on the

26、bed, called ways, and is advanced by a lead screw powered by a motor or hand wheel. Cross slide The cross slide is attached to the top of the carriage and allows the tool to move towards or away from the work-piece, changing the depth of cut. As with the carriage, the cross slide is powered by a mot

27、or or hand wheel. Compound The compound is attached on top of the cross slide and supports the cutting tool. The cutting tool is secured in a tool post which is fixed to the compound. The compound can rotate to alter the angle of the cutting tool relative to the work-piece.Turret Some machines inclu

28、de a turret, which can hold multiple cutting tools and rotates the required tool into position to cut the work-piece. The turret also moves along the work-piece, feeding the cutting tool into the material. While most cutting tools are stationary in the turret, live tooling can also be used. Live too

29、ling refers to powered tools, such as mills, drills, reamers, and taps, which rotate and cut the work-piece. EXERCISE 3 Choose the best operation orders according to the information given. A. Ultra-precision grinding B. Ultra-precision milling C. Ultra-precision turning D. OK E. Too High F. Too LowB

30、CAFDE1. CMI Computer Managed Instruction _2. CRS Cold-rolled Steel _3. CS Complete Self-protecting _4. CO. NI. Copper Nickel Alloy _ 5. DC Direct Current _ 6. DC rel. Direct Current Relay _ 7. DME Distance Measuring Equipment _8. DP Difference of Potential _ EXERCISE 4Abbreviations are very useful i

31、n practical work. Read them and then translate them into corresponding Chinese terms. 計算機管理指令冷軋鋼全自動防護銅鎳合金直流電直流電續(xù)電器測距設備電位差Part II Glance at Conventional Machine Tool Structures The following is the Conventional Machine Tool Structures。 Explanations of the Machine Tool Terms No.NameExplanation1Forward

32、/Reverse正轉(zhuǎn)/反轉(zhuǎn)2Start/Stop啟動/停止3Longitudinal Hand-wheel縱向手輪4Vertical Feed Hand-crank垂直進給手柄5Cross-Feed Hand-wheel橫向進給手輪6Power Feed電動進給7Table工作臺8Spindle主軸9Digital Readout數(shù)字讀數(shù)10Spindle Speed主軸進給11Hand Brake手動制動器EXERCISE 5The following is the Vice Jaw. After reading them, you are required to choose the su

33、itable words or phrases given below. Work-piece Spindle rotor Chuck Spindle Diamond toolAlignment unit Measurement system Pallet Tool magazine Tool magazine Measurement system Spindle Alignment unit Spindle rotor Diamond tool Chuck Pallet Work-piece Part III Simulated WritingSection A Match Your Ski

34、llThe following is the Lathe Accessories, and you can understand the names of Machine Vice. Explanations of the Toll BitsNo.NameExplanation1Twist bits螺旋鉆2Shank柄部3Flute凹槽4Body床身5Flute land 凹槽紋間表面6Land紋間表面7Lead screw絲杠8Solid center auger bit 木工鉆頭9Twist螺旋形10Spur翼EXERCISE 6Complete the information by tr

35、anslating the part given in Chinese. Center Drills High qualityCenter Drillsmanufactured are made of superior quality material which gives the enhanced functional stability. These are used to produce the centre holes in components which need machining between centers. They are superiorfor the centra

36、l holes where precise centering is necessary in subsequent operations. Our Centre Drills conform to IS 6709-1977 and BS 328/Part 2-1950. It has following specifications: IS 6709-1977 (Dimensions in mm) Pilot Dia K12: 2 to 8 Body Dia H9: 8 to 25 Overall length:Max. 52 to 103 Min. 48 to 97 Pilot lengt

37、h: Max. 3.3 to 11.5 Min. 2.5 to 10.1 Section B Have a TryThis section will help you to understand several forms of machining, and you can see the simple way a small part is produced. External Operations Grooving - A turning operation in which a single-point tool moves radially, into the side of the

38、workpiece, cutting a groove equal in width to the cutting tool. If the desired groove width is larger than the tool width, multiple adjacent grooves will be cut. A profiling cut can be performed to smooth the surface of multiple grooves. Special form tools can also be used to create grooves of varyi

39、ng geometries. EXERCISE 7This section is to test your ability to Identifying following features of different operations. Slot cut Grooving Grooving (Form tool) Peripheral cut Slot cutGroovingGrooving (Form tool)Peripheral cutPart IV Broaden Your Horizon - Practical Activity Turning Operations Turnin

40、g is the removal of metal from the outer diameter of a rotating cylindrical work-piece. Turning is used to reduce the diameter of the work-piece, usually to a specified dimension, and to produce a smooth finish on the metal. Chucking the Work-piece We will be working with a piece of 3/4 diameter 606

41、1 aluminum about 2 inches long. We can safely turn it in the three jaw chuck without supporting the free end of the work. Insert the work-piece in the 3-jaw chuck and tighten down the jaws until they just start to grip the work-piece. Rotate the work-piece to ensure that it is seated evenly and to d

42、islodge any chips. You want the work-piece to be as parallel as possible with the center line of the lathe. Imagine an exaggerated example where the work-piece is skewed at an angle in the chuck and you can easily visualize why this is important. Tighten the chuck using each of the three chuck key p

43、ositions to ensure a tight and even grip. Adjusting the Tool Bit Choose a tool bit with a slightly rounded tip. This type of tool should produce a nice smooth finish. Adjust the angle of the tool-holder so the tool is approximately perpendicular to the side of the work-piece. Because the front edge

44、of the tool is ground at an angle, the left side of the tip should engage the work, but not the entire front edge of the tool. The angle of the compound is not critical; I usually keep mine at 90 degrees so that the compound dial advances the work. Cutting Speeds You must consider the rotational spe

45、ed of the work-piece and the movement of the tool relative to the work-piece. Working with the 7x10 for hobby purposes, you will quickly develop a feel for how fast you should go. Until you get a feel for the proper speeds, start with relatively low speeds and work up to faster speeds. Most cutting

46、operations on the 7x10 will be done at speeds of a few hundred RPM - with the speed control set below the 12 Oclock position and with the HI/LO gear in the LO range. Turning with Hand Feed As always, wear safety glasses and keep your face well away from the work since this operation will throw off h

47、ot chips and/or sharp spirals of metal. Now advance the cross slide crank about 10 divisions or .010. Turn the carriage hand-wheel counterclockwise to slowly move the carriage towards the headstock. As the tool starts to cut into the metal, maintain a steady cranking motion to get a nice even cut. I

48、ts difficult to get a smooth and even cut turning by hand. Continue advancing the tool towards the headstock until it is about 1/4 away from the chuck jaws. Obviously you want to be careful not to let the tool touch the chuck jaws! Turning with Power Feed One of the great features of the 7x10 is tha

49、t it has a power lead-screw driven by an adjustable gear train. The lead-screw can be engaged to move the carriage under power for turning and threading operations. To change the lever setting, you must pull back on the knurled sleeve with considerable force. With the sleeve pulled back you can move

50、 the lever up and down to engage its locking pin in one of three positions. In the upper position the lead-screw rotates to move the carriage towards the headstock and in the lower position the lead-screw moves the carriage away from the headstock. In the down position, the half-nut lever engages tw

51、o halves of a split nut around the lead-screw. Make sure the half-nut lever is in the disengaged (up) position. Turn the motor on. The lead-screw should now be rotating counterclockwise. When the lead-screw is engaged the gear train makes kind of an annoying noise, but youll get used to it. Lubricat

52、ing the gear train with white lithium grease will cut down some on the noise. Just as in facing, you normally will make one or more relatively deep (.010-.030) roughing cuts followed by one or more shallow (.001-.002) finishing cuts. Of course you have to plan these cuts so that the final finishing

53、cut brings the work-piece to exactly the desired diameter. When cutting under power, you must be very careful not to run the tool into the chuck. Measuring the Diameter It is important to recognize that, in a turning operation, each cutting pass removes twice the amount of metal indicated by the cross slide feed divisions. The