0041-BL系列臺式車床進(jìn)給結(jié)構(gòu)設(shè)計(jì),bl,系列,臺式,車床,進(jìn)給,結(jié)構(gòu)設(shè)計(jì) 機(jī)械加工介紹（中英文對照） 1 Lathes Lathes are machine tools designed primarily to do turning, facing and boring, Very little turning is done on other types of machine tools, and none can do it with equal facility. Because lathes also can do drilling and reaming, their versatility permits several operations to be done with a single setup of the work piece. Consequently, more lathes of various types are used in manufacturing than any other machine tool. The essential components of a lathe are the bed, headstock assembly, tailstock assembly, and the leads crew and feed rod. The bed is the backbone of a lathe. It usually is made of well normalized or aged gray or nodular cast iron and provides s heavy, rigid frame on which all the other basic components are mounted. Two sets of parallel, longitudinal ways, inner and outer, are contained on the bed, usually on the upper side. Some makers use an inverted V-shape for all four ways, whereas others utilize one inverted V and one flat way in one or both sets, They are precision-machined to assure accuracy of alignment. On most modern lathes the way are surface-hardened to resist wear and abrasion, but precaution should be taken in operating a lathe to assure that the ways are not damaged. Any inaccuracy in them usually means that the accuracy of the entire lathe is destroyed. The headstock is mounted in a foxed position on the inner ways, usually at the left end of the bed. It provides a powered means of rotating the word at various speeds . Essentially, it consists of a hollow spindle, mounted in accurate bearings, and a set of transmission gears-similar to a truck transmission—through which the spindle can be rotated at a number of speeds. Most lathes provide from 8 to 18 speeds, usually in a geometric ratio, and on modern lathes all the speeds can be obtained merely by moving from two to four levers. An increasing trend is to provide a continuously variable speed range through electrical or mechanical drives. Because the accuracy of a lathe is greatly dependent on the spindle, it is of heavy construction and mounted in heavy bearings, usually preloaded tapered roller or ball types. The spindle has a hole extending through its length, through which long bar stock can be fed. The size of maximum size of bar stock that can be machined when the material must be fed through spindle. The tailsticd assembly consists, essentially, of three parts. A lower casting fits on the inner ways of the bed and can slide longitudinally thereon, with a means for clamping the entire assembly in any desired location, An upper casting fits on the lower one and can be moved transversely upon it, on some type of keyed ways, to permit aligning the assembly is the tailstock quill. This is a hollow steel cylinder, usually about 51 to 76mm(2to 3 inches) in diameter, that can be moved several inches longitudinally in and out of the upper casting by means of a hand wheel and screw. The size of a lathe is designated by two dismensions. The first is known as the swing. This is the maximum diameter of work that can be rotated on a lathe. It is approximately twice the distance between the line connecting the lathe centers and the nearest point on the ways, The second size dimension is the maximum distance between centers. The swing thus indicates the maximum work piece diameter that can be turned in the lathe, while the distance between centers indicates the maximum length of work piece that can be mounted between centers. Engine lathes are the type most frequently used in manufacturing. They are heavy-duty machine tools with all the components described previously and have power drive for all tool movements except on the compound rest. They commonly range in size from 305 to 610 mm(12 to 24 inches)swing and from 610 to 1219 mm(24 to 48 inches) center distances, but swings up to 1270 mm(50 inches) and center distances up to 3658mm(12 feet) are not uncommon. Most have chip pans and a built-in coolant circulating system. Smaller engine lathes-with swings usually not over 330 mm (13 inches ) –also are available in bench type, designed for the bed to be mounted on a bench on a bench or cabinet. Although engine lathes are versatile and very useful, because of the time required for changing and setting tools and for making measurements on the work piece, thy are not suitable for quantity production. Often the actual chip-production tine is less than 30% of the total cycle time. In addition, a skilled machinist is required for all the operations, and such persons are costly and often in short supply. However, much of the operator’s time is consumed by simple, repetitious adjustments and in watching chips being made. Consequently, to reduce or eliminate the amount of skilled labor that is required, turret lathes, screw machines, and other types of semiautomatic and automatic lathes have been highly developed and are widely used in manufacturing. 2 Numerical Control One of the most fundamental concepts in the area of advanced manufacturing technologies is numerical control (NC). Prior to the advent of NC, all machine tools ere manually operated and controlled. Among the many limitations associated with manual control machine tools, perhaps none is more prominent than the limitation of operator skills. With manual control, the quality of the product is directly related to and limited to the skills of the operator. Numerical control represents the first major step away from human control of machine tools. Numerical control means the control of machine tools and other manufacturing systems through the use of prerecorded, written symbolic instructions. Rather than operating a machine tool, an NC technician writes a program that issues operational instructions to the machine tool. For a machine tool to be numerically controlled, it must be interfaced with a device for accepting and decoding the programmed instructions, known as a reader. Numerical control was developed to overcome the limitation of human operators, and it has done so. Numerical control machines are more accurate than manually operated machines, they can produce parts more uniformly, they are faster, and the long-run tooling costs are lower. The development of NC led to the development of several other innovations in manufacturing technology: Electrical discharge machining,Laser cutting,Electron beam welding. Numerical control has also made machine tools more versatile than their manually operated predecessors. An NC machine tool can automatically produce a wide of parts, each involving an assortment of widely varied and complex machining processes. Numerical control has allowed manufacturers to undertake the production of products that would not have been feasible from an economic perspective using manually controlled machine tolls and processes. Like so many advanced technologies, NC was born in the laboratories of the Massachusetts Institute of Technology. The concept of NC was developed in the early 1950s with funding provided by the U.S. Air Force. In its earliest stages, NC machines were able to made straight cuts efficiently and effectively. However, curved paths were a problem because the machine tool had to be programmed to undertake a series of horizontal and vertical steps to produce a curve. The shorter the straight lines making up the steps, the smoother is the curve, Each line segment in the steps had to be calculated. This problem led to the development in 1959 of the Automatically Programmed Tools (APT) language. This is a special programming language for NC that uses statements similar to English language to define the part geometry, describe the cutting tool configuration, and specify the necessary motions. The development of the APT language was a major step forward in the fur ther development from those used today. The machines had hardwired logic circuits. The instructional programs were written on punched paper, which was later to be replaced by magnetic plastic tape. A tape reader was used to interpret the instructions written on the tape for the machine. Together, all of this represented a giant step forward in the control of machine tools. However, there were a number of problems with NC at this point in its development. A major problem was the fragility of the punched paper tape medium. It was common for the paper tape containing the programmed instructions to break or tear during a machining process. This problem was exacerbated by the fact that each successive time a part was produced on a machine tool, the paper tape carrying the programmed instructions had to be rerun through the reader. If it was necessary to produce 100 copies of a given part, it was also necessary to run the paper tape through the reader 100 separate tines. Fragile paper tapes simply could not withstand the rigors of a shop floor environment and this kind of repeated use. This led to the development of a special magnetic plastic tape. Whereas the paper carried the programmed instructions as a series of holes punched in the tape, the plastic tape carried the instructions as a series of magnetic dots. The plastic tape was much stronger than the paper tape, which solved the problem of frequent tearing and breakage. However, it still left two other problems. The most important of these was that it was difficult or impossible to change the instructions entered on the tape. To made even the most minor adjustments in a program of instructions, it was necessary to interrupt machining operations and make a new tape. It was also still necessary to run the tape through the reader as many times as there were parts to be produced. Fortunately, computer technology became a reality and soon solved the problems of NC associated with punched paper and plastic tape. The development of a concept known as direct numerical control (DNC) solved the paper and plastic tape problems associated with numerical control by simply eliminating tape as the medium for carrying the programmed instructions. In direct numerical control, machine tools are tied, via a data transmission link, to a host computer. Programs for operating the machine tools are stored in the host computer and fed to the machine tool an needed via the data transmission linkage. Direct numerical control represented a major step forward over punched tape and plastic tape. However, it is subject to the same limitations as all technologies that depend on a host computer. When the host computer goes down, the machine tools also experience downtime. This problem led to the development of computer numerical control. 3 Turning The engine lathe, one of the oldest metal removal machines, has a number of useful and highly desirable attributes. Today these lathes are used primarily in small shops where smaller quantities rather than large production runs are encountered. The engine lathe has been replaced in today’s production shops by a wide variety of automatic lathes such as automatic of single-point tooling for maximum metal removal, and the use of form tools for finish on a par with the fastest processing equipment on the scene today. Tolerances for the engine lathe depend primarily on the skill of the operator. The design engineer must be careful in using tolerances of an experimental part that has been produced on the engine lathe by a skilled operator. In redesigning an experimental part for production, economical tolerances should be used. Turret Lathes Production machining equipment must be evaluated now, more than ever before, this criterion for establishing the production qualification of a specific method, the turret lathe merits a high rating. In designing for low quantities such as 100 or 200 parts, it is most economical to use the turret lathe. In achieving the optimum tolerances possible on the turrets lathe, the designer should strive for a minimum of operations. Automatic Screw Machines Generally, automatic screw machines fall into several categories; single-spindle automatics, multiple-spindle automatics and automatic chucking machines. Originally designed for rapid, automatic production of screws and similar threaded parts, the automatic screw machine has long since exceeded the confines of this narrow field, and today plays a vital role in the mass production of a variety of precision parts. Quantities play an important part in the economy of the parts machined on the automatic screw machine. Quantities less than on the automatic screw machine. The cost of the parts machined can be reduced if the minimum economical lot size is calculated and the proper machine is selected for these quantities. Automatic Tracer Lathes Since surface roughness depends greatly on material turned, tooling , and feeds and speeds employed, minimum tolerances that can be held on automatic tracer lathes are not necessarily the most economical tolerances. In some cases, tolerances of 0.05mm are held in continuous production using but one cut . groove width can be held to 0.125mm on some parts. Bores and single-point finishes can be held to 0.0125mm. On high-production runs where maximum output is desirable, a minimum tolerance of 0.125mm is economical on both diameter and length of turn 2 Simple Machines and Tools A What Do the Simple Machines Mean? Simple machines are devices which allow energy to be transferred from one place to another. With the help of machines our lives are made much easier. To many people the word "machine" means things like a tractor, an electric drill, a bulldozer, a sewing machine or a bicycle. These are machines, but they are really very complicated ones, such as ones made up of many simple machines. There are only a few kinds of simple machines. They are the lever, the wheel and axle, the inclined plane, gears, pulleys and hydraulics. Simple machines can do the following: They allow energy to be transferred from the place where it is available to the place where it is used. They can change the size and direction of force. Certain types of machines allow us to apply a very large force to something by using a small force. This is called a force advantage. They can change the distance and speed with which something is moving. This is called giving a distance or speed advantage. A typical example of simple machines is the lever, which has found extremely wide use in our production practice. Some other simple machines can be seen like a seesaw, an axe, a wheelbarrow, a pair of scissors and a hammer. These are examples of levers. By using these, tasks which would be difficult for you to do can be done more easily. A lever is a rigid bar. The crowbar in Figure 1 is an example of a simple lever. All levers have the following parts: 1. The fulcrum is the fixed point around which the lever can turn. 2. The effort force is the force applied to the lever. It is sometimes called the input force or simply the effort. 3. The effort arm is the distance between the fulcrum and the point where the effort force is applied. 4. The load force is the force moving the load. It is the output force of the lever and is sometimes simply called the load. 5. The load arm is the distance from the fulcrum to the position of the load. A wheelbarrow allows us to lift a heavy load by using a fairly small force. The wheelbarrow can be draw as a rigid bar as is shown in figure 2. the wheel axle acts as the fulcrum. It can easily be seen that the effort arm is longer than the load arm. This gives a force advantage because the load force is greater than the effort force that is applied. However, the effort force has to be moved much further than the load. Fig.1 A crow-bar Fig.2 A wheelbarrow If the fulcrum is placed so that the load arm is longer than the effort arm, a large force is needed to move a small load, but it moves the load a long way. This gives a speed advantage. This idea can be seen in the fishing rod. The large effort force applied by the fisherman moves only a small load, the fish. However itdoes allow the fisherman to drag the fish in quickly. Often simple machines are made of double levers. Scissors, pliers, nutcrackers and tinsnips are all double levers. double levers 雙重杠桿 effort arm 力臂 effort force 作用力 force advantage 力增益 in a more convenient way 以某種較為方便的方式 inclined plane 斜面 load arm 重力臂 load force 荷載力（重力） rigid bar 剛性桿 speed advantage 速度增益 input force 輸入力 文中為作用力 output force 輸出力 文中為載荷力或阻力 B Tools and Machines Each department in manufacturing uses tools to do its job. In general, tools and machines process (change) materials or information. Production department workers use tools to change materials into finished products. The finance department uses calculators and computers to keep track of the company's finances. Marketing workers send product information to consumers through advertisements made with video and audio recording machines. Workers in manufacturing must know how to use the tools of their trade. Defining tools and machines Tools extend human abilities in doing the work of processing (changing) materials or information. So, strictly speaking, machines are also tools. Tools extend human abilities by increasing the power, speed, efficiency, accuracy, and productivity of work. We cannot drive nails in boards with our bare hands, but we can drive nails with a tool – the hammer. We can do math problems in our head, but an electronic calculator is faster and more accurate. Both the hammer and the calculator are tools that extend our abilities. Generally, tools can be described as hand tools, power hand tools, or machines. A hand tool is the simplest form. The user holds it in the hand and moves it to perform work. It is powered only by the user. Hand saws, screwdrivers, and hand planes are examples of hand tools. Power hand tools are improved hand tools. The user holds one in the hand and moves it to perform work, but the processing power comes from an external source, such as an electric motor. Power circular saws, electric screwdrivers, and power planes are some power hand tools. Machines stay still during processing and use an externally powered tool that is fastened to the machine to do the actual processing. Table saws, drill presses, and planers are all machines. Another category of manufacturing tools is equipment. Equipment covers devices that cannot be defined as machine, power hand tools, or hand tools. Equipment stays still on a structure during processing and uses human or thermal (heat) power too process materials. Examples include the human-powered squaring shears for shearing metal and ovens, and furnaces used to melt materials. All tools, machines, and equipment extend human abilities by increasing the power, speed, efficiency, accuracy, and productivity of processing materials or information. The six basic machines We base the principles that describe how tools work on the basic machines – wheelsevers, pulleys, inclined planes, wedges, and screws, (see the fig.). The purpose of these basic machines is to gain a mechanical advantage in doing work. A mechanical advantage is an increase in a force. Mechanical advantage of force is abbreviated MAF. A simple example is driving nails in wood. Without a hammer, you would not be able to drive the nails. By placing the hammer in your hand, you create a lever that gives you a mechanical advantage of force over the nail. The nail itself uses wedge action to cut into the wood. For anther example, look at the frill press, often found in labs. The drill bit uses a wedge for its cutting action. Inclined planes hold the drill bit in the chuck. Screw threads hold the drill press together. Pulleys transfer power from the motor to the drill bit. The handle on the drill press acts as a lever attached to a wheel and axle. Every time one of the six basic machines is used in a tool or machine, mechanical advantage is realized. Identify the six basic machines in other tools and machines in your lab. dri