电动螺旋起重机设计[机电电动举高器类型]【全套10张CAD图纸和WORD毕业论文】

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关键词：: 电动螺旋起重机设计全套 cad 图纸 word 毕业论文

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摘要
螺旋起重机又称为螺旋升降机，它的原型就是我们所常见的千斤顶。它具有结构紧凑、体积小、重量轻、动力源广泛、无噪音、安装方便、使用灵活、功能多、配套形式多、可靠性高、使用寿命长等许多优点。可以单台或组合使用，能大致控制调整提升的高度，可以用电动机或其他动力直接带动，也可以手动。
电动螺旋起重机基本原理是利用电机，通过减速器减速后，带动螺母旋转，转化为丝杆的轴向运动，从而推动物体上升。主要内容如下：对千斤顶的原理和螺旋起重的原理、方法进行了研究；设计螺旋起重机构；选择电动机；设计减速机构；控制电路的设计；简要阐述在流水线作业中，螺旋千斤顶的动作原理等。
关键词千斤顶；电动；螺旋传动

Abstract
摘要英文删除下载后有原版，如有疑问可以咨询QQ 414951605 截取查看

目录
1 绪论 1
1.1千斤顶的发展现状 1
1.2千斤顶的分类 2
2 设计方案的确定 3
2.1螺旋传动设计方案 3
2.1.1螺旋传动概述 3
2.1.2螺旋传动方案的确定 4
2.2减速传动机构设计方案 5
3 传动系统的设计 6
3.1螺旋传动部分计算 6
3.1.1螺杆直径的计算 6
3.1.2螺纹部分强度计算 6
3.2电机的选择 8
3.2.1电动机功率计算 9
3.2.2传动效率 9
3.2.3确定电机转速 10
3.3减速机构的设计 11
3.3.1材料的选择 11
3.3.2蜗轮蜗杆传动基本尺寸 12
3.3.3强度校核 15
3.3.4蜗轮蜗杆传动中的作用力分析 15
3.3.5实际传动动力参数 16
4 辅助装置的设计 18
4.1轴承的选择 18
4.1.1轴承的选择因素 18
4.1.2轴承的型号确定 19
4.1.3轴承校验 19
4.2键的选择 22
4.3联轴器的设计与计算 23
5 控制电路及过载保护系统的设计 25
5.1 过载及最大行程保护元件 25
5.1.1 热继电器 25
5.1.2 行程开关 26
5.2电器控制基本电路设计 28
6 系统的改进与优化 30
6.1力学传感器 30
6.1.1电阻应变片力传感器 30
6.2位置传感器 32
6.3连续控制分析 34
结论 35
致谢 36
参考文献 37
附录 38
附录1 38
附录2 49

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内容简介：: 徐州工程学院毕业设计（论文）开题报告课题名称：电动螺旋起重机设计学生姓名：徐新明学号： 20040601411指导教师：陈跃职称：讲师所在学院：机电工程学院专业名称：机械设计制造及自动化徐州工程学院2008 年 3月 4 日说明1根据徐州工程学院毕业设计(论文)管理规定，学生必须撰写毕业设计（论文）开题报告，由指导教师签署意见、教研室审查，学院教学院长批准后实施。2开题报告是毕业设计（论文）答辩委员会对学生答辩资格审查的依据材料之一。学生应当在毕业设计（论文）工作前期内完成，开题报告不合格者不得参加答辩。3毕业设计开题报告各项内容要实事求是，逐条认真填写。其中的文字表达要明确、严谨，语言通顺，外来语要同时用原文和中文表达。第一次出现缩写词，须注出全称。4本报告中，由学生本人撰写的对课题和研究工作的分析及描述，没有经过整理归纳，缺乏个人见解仅仅从网上下载材料拼凑而成的开题报告按不合格论。5. 课题类型填：工程设计类；理论研究类；应用（实验）研究类；软件设计类；其它。6、课题来源填：教师科研；社会生产实践；教学；其它课题名称小型电动螺旋起重机设计课题来源模拟生产实际课题课题类型工程应用选题的背景及意义本课题来源于模拟生产实际,属于工程应用。起重机是当代最为得力的起重设备之一。随着国民经济的不断发展,多种类型的起重机广泛的运用于冶金、矿山、水泥、码头、化工、粮食等行业的各种场合。同时在各种场合对不同的工况所使用的起重机也不尽相同，近年来由于起重机的应用范围的扩大，品种的增多以及质量的不断提高，对加工设计起重机提出了更高的要求。本设计所研究的电动螺旋起重机，又称作电动螺旋升降机，它的原形也就是我们众所周知的千斤顶。随着社会的发展，解放劳动力，采用电动成了必然。因此本设计采用电机驱动，开发出新的产品。研究内容拟解决的主要问题研究内容：1 电动螺旋起重机机械机构设计2 一级齿轮减速机构设计工作量：1A0图纸三张，分别为系统装配图和各零件图2毕业设计说明书一本（2万字）；3相关外文资料翻译（5000字）。解决问题：根据起重重量的大小，设计出相应的螺旋起重机构，根据起重的速度设计出相应的减速机构，以及箱体、选择电机等。研究方法技术路线基本研究方法：利用电机，通过减速器减速后，带动螺母旋转，转化为丝杆的轴向运动，从而推动物体上升。基本研究技术路线：研究千斤顶原理，设计螺旋起重机构；选择电动机；设计减速机构；控制电路的设计；简要阐述在流水线作业中，螺旋千斤顶的动作原理等。研究的总体安排和进度计划第1周：了解设计的基本要求，查阅相关资料第2周：查阅相关资料，写开题报告第3周：外文资料翻译第4周：设计方案比较选择第5周：机械部分总体设计第6周：机械部分设计计算第7周：机械部分设计计算第8周：传动系统设计计算第9周：传动系统设计计算第10周：电机选择计算第11周：绘制机械装配图第12周：绘制机械零件图第13周：撰写毕业设计说明书第14周：撰写毕业设计说明书第15周：答辩准备第16周：答辩主要参考文献1 邱宣怀.机械设计.第四版. 高等教育出版社, 2003.42 龚湘义. 机械设计课程设计指导书.第二版.高等教育出版社.2004.23 张建中. 机械设计基础课程设计. 中国矿业大学出版社, 2005.24 哈尔滨工业大学龚湘义. 机械设计课程设计图册.第三版. 高等教育出版社, 2004.1 5 实用机械设计手册编写组.实用机械设计手册.第二版.机械工业出版社6 范思冲等编著画法几何及机械制图. 机械工业出版社7 李洪、曲中谦. 实用轴承手册. 辽宁科学技术出版社8 杨黎明. 传感器技术. 国防工业出版社 9 徐寅主编，机械设计手册.北京，机械工业出版社，1991指导教师意见指导教师签名：年月日教研室意见学院意见教研室主任签名：年月日教学院长签名：年月日徐州工程学院毕业设计(论文)摘要螺旋起重机又称为螺旋升降机，它的原型就是我们所常见的千斤顶。它具有结构紧凑、体积小、重量轻、动力源广泛、无噪音、安装方便、使用灵活、功能多、配套形式多、可靠性高、使用寿命长等许多优点。可以单台或组合使用，能大致控制调整提升的高度，可以用电动机或其他动力直接带动，也可以手动。电动螺旋起重机基本原理是利用电机，通过减速器减速后，带动螺母旋转，转化为丝杆的轴向运动，从而推动物体上升。主要内容如下：对千斤顶的原理和螺旋起重的原理、方法进行了研究；设计螺旋起重机构；选择电动机；设计减速机构；控制电路的设计；简要阐述在流水线作业中，螺旋千斤顶的动作原理等。关键词千斤顶；电动；螺旋传动AbstractThe spiral crane is also known as the spiral screw lift crane .Its prototype is the jack as we common see. Its advantages as follows: small size, light weight, extensive power source, no noise, ease of installation, flexible, multi-function, supporting forms, high reliability and long service life, and so on. It can be used single or in combination, and can generally control the height. Motor can be used directly or other power driven, besides ,it can also be manually.And the basic principle is that the motor drives the rotary nut through the deceleration agencies, screw into the axial campaign, and then lift the objects .The main contents as follows: research the principle of spiral jack and the principles and methods of the spiral lifting, design the agencies of spiral lifting; motor choice; design deceleration agencies; select keys and bearings, design the control circuit; describe the principle of the screw jack on the assembly line operation.Keywords Spiral jack Electrical Spiral driveII徐州工程学院毕业设计(论文)目录1 绪论11.1千斤顶的发展现状11.2千斤顶的分类22 设计方案的确定32.1螺旋传动设计方案32.1.1螺旋传动概述32.1.2螺旋传动方案的确定42.2减速传动机构设计方案53 传动系统的设计63.1螺旋传动部分计算63.1.1螺杆直径的计算63.1.2螺纹部分强度计算63.2电机的选择83.2.1电动机功率计算93.2.2传动效率93.2.3确定电机转速103.3减速机构的设计113.3.1材料的选择113.3.2蜗轮蜗杆传动基本尺寸123.3.3强度校核153.3.4蜗轮蜗杆传动中的作用力分析153.3.5实际传动动力参数164 辅助装置的设计184.1轴承的选择184.1.1轴承的选择因素184.1.2轴承的型号确定194.1.3轴承校验194.2键的选择224.3联轴器的设计与计算235 控制电路及过载保护系统的设计255.1 过载及最大行程保护元件255.1.1 热继电器255.1.2 行程开关265.2电器控制基本电路设计286 系统的改进与优化306.1力学传感器306.1.1电阻应变片力传感器306.2位置传感器326.3连续控制分析34结论35致谢36参考文献37附录38附录138附录2492徐州工程学院毕业设计(论文)附录附录1英文原文CNC TECHNOLOGYNumerical control (NC) is a form of programmable automation in which the processing equipment is controlled by means of numbers, letters, and other symbols. The numbers, letters, and symbols are coded in an appropriate format to define a program of instructions for a particular workpart or job. When the job changes, the program of instructions is changed. The capability to change the program is what makes NC suitable for low-and medium-volume production. It is much easier to write new programs than to make major alterations of the processing equipment.BASIC COMPONENTS OF NCA numerical control system consists of the following three basic components:Program of instructionsMachine control unitProcessing equipmentThe general relationship among the three components is: the program is fed into the control unit, which directs the processing equipment accordingly.The program of instructions is the detailed step-by-step commands that direct the processing equipment. In its most common form, the commands refer to positions of a machine tool spindle with respect to the worktable on which the part is fixtured. More advanced instructions include selection of spindle speeds, cutting tool, and other function. The most common medium in use over the last several decades has been 1-in. -wide punched tape. Because of the widespread use of the punched tape, NC is sometimes called “tape control”. However, this is a misnomer in modern usage of numerical control. Coming into use more recently have been magnetic tape cassettes and floppy diskettes.The machine control unit (MCU) consists of the electronics and control hardware that read and interpret the program of instruction and convert it into mechanical actions of the machine tool or other processing equipment.The processing equipment is the third basic component of an NC system. It is the component that performs useful work. In the most common example of numerical control, one that performs machining operations, the processing equipment consists of the worktable and spindle as well as the motors and controls needed to drive them.Types Of Control SystemsThere are two basic types of control systems in numerical control: point-to-point and contouring. In the point-to-point system, also called positioning, each axis of the machine is driven separately by leadscrews and, depending on the type of operation, at different velocities. The machine moves initially at maximum velocity in order to reduce nonproductive time but decelerates as the tool reaches its numerically defined position. Thus in an potation such as drilling or punching, the positioning and cutting take place sequentially. After the hole is drilled or punched, the tool retracts, moves rapidly to another position, and repeats the operation. The path followed from one position to another is important in only one respect: The time required should be minimized for efficiency. Point-to-point systems are used mainly in drilling, punching, and straight milling operations.In the contouring system, also known as the continuous path system, positioning and cutting operations are both along controlled paths but at different velocities. Because the tool cuts as it travels along a prescribed path, accurate control and synchronization of velocities and movements are important. The contouring system is used on lathes, milling machines, grinders, welding machinery, and machining centers.Movement along the path, or interpolation, occurs incrementally, by one of several basic methods. In all interpolations, the path controlled is that of the center of rotation of the tool. Compensation for different tools, different diameter tools, or tool wear during machining, can be made in the NC program.There are a number of interpolation schemes that have been developed to deal with the various problems that are encountered in generating a smooth continuous path with a contouring-type NC system. They include:Linear interpolationCircular interpolationHelical interpolationParabolic interpolationCubic interpolationEach of these interpolation procedures permits the programmer (or operator) to generate machine instructions for linear or curvilinear paths, using a relatively few input parameters. The interpolation module in the MCU performs the calculations and directs the tool along the path.Linear interpolation is the most basic and is used when a straight-line path is to be generated in continuous-path NC. Two-axis and three-axis linear interpolation routines are sometimes distinguished in practice, but conceptually they are the same. The program is required to specify the beginning point and end point of the straight line, and the feed rate that is to be followed along the straight line. The interpolator computes the feed rates for each of the two (or three) axes in order to achieve the specified feed rate.Linear interpolation for creating a circular path would be quite inappropriate because the programmer would be required to specify the line segments and their respective end points that are to be used to approximate the circle. Circular interpolation schemes have been developed that permit the programming of a path consisting of a circular arc by specifying the following parameters of the arc: the coordinates of its end points, the coordinates of its center, its radius, and the direction of the cutter along the arc. The tool path that is created consists of a series of straight-line segments, but the segments are calculated by the interpolation module rather than the programmer. The cutter is directed to move along each line segment one by one in order to generate the smooth circular path. A limitation of circular interpolation is that the plane in which the circular arc exists must be a plane defined by two axes of the NC system.Helical interpolation combines the circular interpolation scheme for two axes described above with linear movement of a third axis. This permits the definition of a helical path in three-dimensional space.Parabolic and cubic interpolation routines are used to provide approximations of free-form curves using higher-order equations. They generally require considerable computational power and are not as common as linear and circular interpolation. Their applications are concentrated in the automobile industry for fabricating dies for car body panels styled with free-form designs that cannot accurately and conveniently be approximated by combining linear and circular interpolations.Programming For NCA program for numerical control consists of a sequence of directions that causes an NC machine to carry out a certain operation, machining being the most commonly used process. Programming for NC may be done by an internal programming department, on the shop floor, or purchased from an outside source. Also, programming may be done manually or with computer assistance.The program contains instructions and commands. Geometric instructions pertain to relative movements between the tool and the work piece. Processing instructions pertain to spindle speeds, feeds, tools, and so on. Travel instructions pertain to the type of interpolation and slow or rapid movements of the tool or worktable. Switching commands pertain to on/off position for coolant supplies, spindle rotation, direction of spindle rotation, tool changes, work piece feeding, clamping, and so on.(1) Manual Programming Manual part programming consists of first calculating dimensional relationships of the tool, work piece, and work table, based on the engineering drawings of the part, and manufacturing operations to be performed and their sequence. A program sheet is then prepared, which consists of the necessary information to carry out the operation, such as cutting tools, spindle speeds, feeds, depth of cut, cutting fluids, power, and tool or work piece ally a paper tape is first prepared for trying out and debugging the program. Depending on how often it is to be used, the tape may be made of more durable Mylar.Manual programming can be done by someone knowledgeable about the particular process and able to understand, read, and change part programs. Because they are familiar with machine tools and process capabilities, skilled machinists can do manual programming with some training in programming. However, the work is tedious, time consuming, and uneconomical-and is used mostly in simple point-to-point applications.(2) Computer-Aided Programming Computer-aided part programming involves special symbolic programming languages that determine the coordinate points of corners, edges, and surfaces of the part. Programming language is the means of communicating with the computer and involves the use of symbolic characters. The programmer describes the component to be processed in this language, and the computer converts it to commands for the NC machine. Several languages having various features and applications are commercially available. The first language that used English-like statements was developed in the late 1950s and is called APT (for Automatically Programmed Tools). This language, in its various expanded forms, is still the most widely used for both point-to-point and continuous-path programming.Computer-aided part programming has the following significant advantages over manual methods: Use of relatively easy to use symbolic languageReduced programming time. Programming is capable of accommodating a large amount of data concerning machine characteristics and process variables, such as power, speeds, feed, tool shape, compensation for tool shape changes, tool wear, deflections, and coolant use. Reduced possibility of human error, which can occur in manual programming Capability of simple changeover of machining sequence or from machine to machine. Lower cost because less time is required for programming.Selection of a particular NC programming language depends on the following factors:a)Level of expertise of the personnel in the manufacturing facility.b)Complexity of the part.c)Type of equipment and computers available.d)Time and costs involved in programming.Because numerical control involves the insertion of data concerning work piece materials and processing parameters, programming must be done by operators or programmers who are knowledgeable about the relevant aspects of the manufacturing processes being used. Before production begins, programs should be verified, either by viewing a simulation of the process on a CRT screen or by making the part from an inexpensive material, such as aluminum, wood, or plastic, rather than the material specified for the finished part.Cutting tool choice and cutting specifications determination in CNC processingThe cutting tool choice and the cutting specifications determination is in the numerical control processing craft important content, it not only influence numerical control engine bed processing efficiency, moreover affects the processing quality directly. CAD/The CAM technology development, enables in the numerical control processing to become directly using the CAD design data possibly, specially the microcomputer and the numerical control engine bed joint, causes the design, the craft plan and the programming entire process completes completely on the computer, does not need to output the special technological document generally.Now, many CAD/The CAM software package all provides the automatic programming function, these software are generally prompt the craft plan in the programming contact surface the related question, for instance, cutting tool choice, processing way plan, cutting specifications hypothesis and so on, programmers so long as have established the related parameter, may automatically produce completes the processing the NC procedure and the transmission to the numerical control engine bed. Therefore, in the numerical control processing cutting tool choice and the cutting specifications determination is completes under the man-machine interactive condition, this forms the sharp contrast with the ordinary engine bed processing, at the same time also requests the programmers to have to grasp the cutting tool choice and the cutting specifications determination basic principle, when programming full consideration numerical control processing characteristic. This article the cutting tool choice and the cutting specifications which must face to the numerical control programming in determined the question has carried on the discussion, has produced certain principles and the suggestion, and to the question which should pay attention has carried on the discussion.First, numerical control processing commonly used cutting tool type and characteristicThe numerical control processing cutting tool must adapt the numerical control engine bed high speed, is highly effective and the automatic high characteristic, should include the general cuttingtool, the general connection hilt and the few special-purpose hilts generally. The hilt must join the cutting tool and install on the engine bed power head, therefore already gradual standardization and seriation. The numerical control cutting tool classification has the many kinds of methods. May divide into according to the cutting tool structure: (1) Integral type; (2) The mosaic, uses the welding or machine clamps the type connection, machine clamps the type to be possible to divide into does not index and may index two kinds; (3) Special pattern, like compound expression cutting tool, absorption of shock type cutting tool and so on. According to makes the materialwhich the cutting tool uses to be possible to divide into: (1) High-speed steel cutting tool; (2) Hard alloy tools; (3) Diamond cutting tool; (4) Other material cutting tools, like cubic boron nitride cutting tool, ceramic cutting tool and so on. May divide into from the cutting craft: (1) The turning cutting tool, divides the outer annulus, in the hole, the thread, cuts the cutting tool many kinds of and so on; (2) Drills truncates the cutting tool, including drill bit, reamer, screw tap and so on; (3) Boring cutting tool; (4) Milling cutting tool and so on. In order to adapt the numerical control engine bed durably to the cutting tool, is stable, easy change, may trade and so on the request, in recent years machine clamps the type to be possible to index the cutting tool to obtain the widespread application, reaches higher authorities in the quantity to the entire numerical control cutting tool 30% 40%, the metal excision quantity accounts for the total 80% 90%. Machining CentersMany of todays more sophisticated lathes are called machining centers since they are capable of performing, in addition to the normal turning operations, certain milling and drilling operations. Basically, a machining center can be thought of as being a combination turret lathe and milling machine. Additional features are sometimes included by manufacturers to increase the versatility of their machines.Numerical ControlOne 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 were 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:1. Electrical discharge machining.2. Laser cutting.3. 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 variety 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 tools 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 make 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 is 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 further development of NC technology. The original NC systems were vastly different 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 times. 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 tape carried the programmed instructions as a series of holes punched in the tape, the plastic tape carried the 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 taps, 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 make 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 as 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 lost computer goes down, the machine tools also experience downtime. This problem led to the development of computer numerical control.The development of the microprocessor allowed for the development of programmable logic controllers (PLCs) and microcomputers. These two technologies allowed for the development of computer numerical control (CNC).With CNC, each machine tool has a PLC or a microcomputer that serves the same purpose. This allows programs to be input and stored at each individual machine tool. It also allows programs to be developed off-line and downloaded at the individual machine tool. CNC solved the problems associated with downtime of the host computer, but it introduced another known as data management. The same program might be loaded on ten different microcomputers with no communication among them. This problem is in the process of being solved by local area networks that connect microcomputers for better data management.Tool ChangerThe machining center is equipped whit a programmable automatic tool changer. Depending on the design, up to 200 cutting tools can be stored in a magazine, drum or chain(tool storage). Auxiliary tool storage is available on some special machining centers for many more cutting tools. The cutting tools are automatically selected with random access for the shortest route to the machine spindle. The tool-exchange arm shown Fig.4.5 is a common design. (See also Fig.4.2).It swings around to pick up a particular tool(each tool has its own tool holder)and places it in the spindle.Tools are indentified by coded tags, bar codes, or memory chips attached directly to the tool holders. A tool-changing time is typically between 5 and 10 seconds; they may be less than one second for small tools, or up to 30seconds for tools weighing 110kg(250lb). The trend in tool changers is to use simple mechanisms, resulting in faster tool-changing times.Machining centers may be equipped with a tool-and/or part-checking station that feeds information to the computer-numerical control to compensate for any variations in tool settings or tool wear. Touch probes(Fig.4.6)can be automatically installed into a tool holder to determine reference surfaces of the work piece, for the selection of tool setting, and for the on-line inspection of parts being machined.Note in Fig.4.6 that several surfaces can be contacted, and that their relative positions are determined and stored in the database of the computer software. The data are then used to program tool paths and to compensate for tool length and diameter, as well as for tool wear in more advanced machine tools.Types of Machining and Turning CentersAlthough there are various designs for machining centers, the two basic types are vertical spindle and horizontal spindle; many machines are capable of using both axes. The maximum dimensions that the cutting tools can reach around a work piece in a machining center is known as the work envelop; this term was first used in connection with industrial robots.Vertical-spindle machining centers, or vertical machining centers, are suitable for performing various machining operations on flat surfaces with deep cavities-for instance, mold and die making. A vertical-spindle machining center, which is similar to a vertical-spindle milling machining, is shown in Fig.4.7. The tool magazine is on the left of the figure and all operations and movements are directed and modified through the computer-control panel on the right.Because the thrust forces in vertical machining are directed downward, such machines have high stiffness and produce parts with good dimensional accuracy. These machines are generally less expensive than horizontal-spindle machines.Horizontal-spindle machining centers, or horizontal machining centers, are suitable for larger as well as tall work piece that require machining on a number of their surfaces. The pallet can be swiveled on different axes(Fig.4.3)to various angular positions.Another category of horizontal-spindle machines is processing centers, which are computer-controlled lathes with several features. A three-turret computer numerical-controlled turning center is shown in Fig.4.8. This machine is designed with tow horizontal spindles and three turrets equipped with a variety of cutting tools used to perform several operations on a rotating work piece.Universal machining centers are equipped with both vertical and horizontal spindles. They have a variety of features and are capable of machining all surfaces of a work piece(vertical, horizontal, and diagonal).Characteristics and Capabilities of Machining CentersThe following are the major characteristics of machining centers:They are capable of handling a variety of part size and shapes efficiently, economically, and with repetitively high dimensional accuracy ;dimensional tolerances are on the order of 0.0025mm(0.0001in).The machines are versatile, having as many as six axes of linear and angular movements, and are capable of quick changeover from one type of product to another, so the need for a variety of machine tools and floor space is significantly reduced.The time required for loading and unloading work piece, changing tools, gaging, and troubleshooting is reduced, so productivity is improved, reducing labor requirements(particularly for skilled labor)and minimizing production costs.They are highly automated and relatively compact, so that one operator can attend two or more machines at the same time.The machines are equipped with tool-condition monitoring devices for the detection of tool breakage and wear, as well as probes for tool-wear compensation and for tool positioning.In-process and post-procwss gaging and inspection of machined work pieces are now features of machining center.Machining centers are available in a wide variety of size and features, and their costs range uo 75KW(100hp) and maximum spindle speeds are usually in the range of 4000-8000rpm; some are as high as 75000rpm for special applications using small-diameter cutters. Some pallets are capable of supporting work piece weighing as much as 7000kg(15000lb), although higher capacities are available for special applications.Many machines are now being constructed on a modular basis, as that various peripheral equipment and accessories can be installed and modified as the demand for different types of products changes.Because of the high productivity of machining centers, large amounts of chips are produced and must be controlled and disposed of properly several designs are available for chip collection, one example of which is shown in Fig.4.9. Note the two chip conveyors at the bottom of the cross-sectional view of a portion of a horizontal-spindle machining center. These particular converyors are of the spiral(screw) type; they collec chips along the two toughs and deliver them to a collection pint. Other systems may use chain-type conveyors.Machine-tool SelectionMachining centers can require significant capital expenditures, so to be cost effective, they generally have to be used for at least two shifts per day. Consequently, there must be sufficient and continued demang for products made in machining centers to justify this purchase. Because of their inherent versatility, however, machining centers can be used to produced a wide range of products, particularly with just-in-time manufacturing.The selection of the type and size of machining centers depends on several factors, among which are the following:The type of products, their size, and their shape complexityThe type of machining operations to be performed and the type and number of cutting tools requiredThe dimensional accuracy requiredThe production rate requiredAlthough versatility is the key factor in the selection of machining centers, these considerations must be weighed against the high captal investment requires and compared to the cost of manufacturing the same products using a number of more traditional machine tools.附录2中文译文CNC技术数控（NC）是可编程的自动化的一种形式。其加工设备由一系列的数字、字母和其他符号控制。这些数字、字母和符号被编成一定的格式，以便为一个特定的工步或者工作定义一个指令程序。当工作改变时，指令程序也随之改变。这种改变程序的能力使NC适应小、中批量生产。编写新的程序要比大批量调换生产设备容易的多。NC的基本组成部分一个数控系统包括以三个组成部分：l 指令编程l 机械控制单元l 加工设备三者之间的关系是：程序导入控制单元，控制单元直接指导加工设备的动作。指令程序是细化的一步步的命令，它控制加工设备。在它的一般形式中，命令涉及到机床主轴和放置工件的工作台的相对位置。许多先进的指令包含有选择主轴速度，切削工具等功能。程序编在一个适当的媒介中，再导入到控制单元中。在几十年前最常用的媒介是一英尺宽的穿孔纸带。由于穿孔纸带的广泛应用，NC也叫做“纸带控制”。现在磁带和软盘得到了广泛的应用。加工设备的NC系统的第三个基本组成部分。它是有效工作的执行部分。在许多数控的例子中，加工设备包括工作台、主轴和驱动和控制它们的设备。控制系统的种类在NC中有两种基本控制类型：点到点和仿型定位。在点到点系统中（也叫做点定位），机床的每一个轴都单独驱动。为了减少不加工时间，机床一最大的速度运动。但刀具达到定位点时开始减速。因此在一个加工过程中，比如钻削或冲压，加工过程和回程独立完成。在孔被钻出或冲出后，刀具撤回，移动到另一个地方，继续下一次加工。从一点到另一点的路径在一个放面十分重要：为提高效率，所需时间必须最小。点定位主要用于钻削、虫牙和立式洗削加工。在仿型定位系统中（也被称为沿路径加工系统），定位和加工都沿着指定的路径，但速度不一样。因此刀具沿着指定的路径运动，速度和运动的同步精确控制十分重要。仿型定位系统用于车床、磨床、焊接机械和加工中心中。在几种基本方法之一的控制之下，刀具沿着路径发生微量的移动。在NC程序中，不同的刀具有不同的刀具补偿。为使仿型数控加工中有光滑的路径，开发了许多补偿方式用以处理这些问题。他们包括：l 直线插补l 圆弧插补l 螺旋插补l 抛物线插补l 三次曲线插补直线插补是最基本的。当仿型加工路线是直线时用到它。两轴和三轴直线插补在实际运用中有一定的区别，但概念上是一致的。程序需要指定直线的起点和终点，并指定沿直线的进给速度。为了得到指定的沿直线的进给速度，插补要计算出两轴（三轴）的每一轴的进给速度。如果要创建一个圆弧路径，直线插补是不合适的。因为程序需要指定圆弧和它们各自的终点。圆弧插补已经发展了。它允许路径的程序包含圆弧，这个圆弧由以下参数定义：终点坐标、圆弧中心坐标、半径和沿圆弧加工的方向。创造出的刀具路径包含一系列的直线线段，但这些线段由插补模型计算，而不是程序本身。刀具沿着每一条线段一条接一条的移动，加工出光滑的圆弧路径。圆弧插补的限制是圆弧存在的平面必须在一个由CNC系统的二轴定义的平面内。螺旋插补使两轴描述的圆弧插补和第三轴的直线运动结合了起来。它允许在在三维空间里定义一个三维的路径。抛物线和三次曲线插补利用一个高阶方程提供一个复杂的自由曲线。它们通常需要很大的计算量，因此不如直线和圆弧插补常用。它们用于自动化工业的模具制造中。这些设计中不能精确和方便的由直线和圆弧插补近似。加工工具的选择和加工工艺规程的制定加工工具的选择和加工工艺规程的制定是数控加工的一个重要的内容，它不仅影响到数控加工的效率，还直接影响到加工质量。CAD/CAM技术的发展，使数控加工能直接运用CAD设计数据，特别是微机和数控模块，使设计工艺过程和编程的全过程都由计算机完成，而不需要输出特定的技术文件。如今，许多CAD/CAM软件包都提供自动编程功能，这些软件即时更新编程中遇到的问题，加工刀具的选择，加工方式的计划和加工规范的制定等等。编程人员只需建立先关的参数，就可以自动完成数控生产，还可以与数控模块通信。因此，在数控加工中，刀具的选择和加工规范的制定完全取决于机床的条件。与此同时也需要编程人员掌握刀具的选择和工艺规范的制定原则，因为编程须完全考虑数控加工的特征。数控加工经常使用的刀具种类和特征数控加工刀具必须适应高速性，高效性和自动高级特征，应该包括一般刀具和特殊用途的刀具。数控刀具的划分有多种方法。许多刀具通过其结构划分成：（1）整体式刀具（2）装配式刀具。运用焊接或者机械加紧方式。机械加紧式又可以分为可转位和不可转位两种。按刀具的材料可分为高速钢（1）高速钢刀具（2）硬质合金刀具（3）金刚石刀具（4）其他材料刀具。如立方碳化硼刀具，陶瓷刀具等等。还有按切削工艺可分为（1）成型刀具（2）钻孔刀具。包括麻花钻、扩孔钻，忽刀等等（3）镗刀（4）铣刀等等。为了适应数控机床对刀具稳定性、易更换性等的要求，近几年装配式的可转位刀具得到了普遍的应用。占到整个数控机床刀具的30%-40%，金属的数量达到80%-90%。数控程序一个数控程序包含一系列的能使数控机床正确加工的指令。NC程序由内置程序完成，在商品架上或者从外部资源购买。程序也可以手工或者计算机辅助编程。程序包括指令和命令，G指令定义刀具和工件间的相互运动。P指令定义主轴转速、进给速度、刀具等。T指令定义插补号和工作台或刀具的快、慢移动。S指令定义主轴转动、换刀和工件的进给等等。（1）手工编程手工编程首先计算刀具、工件和工作台的相互位置关系。它基于工程图和制造工艺和它们的顺序。然后准备好一个表，其中包括加工特定工序所需的必要信息。例如：切削刀具、主轴转速、进给速度、切削深度、切削液、切削力、刀具或者工件的相对位置和运动。有了这些信息，程序部分就准备好了。通常输出程序的纸带要先准备好。手工编程可以由懂得特定加工过程的专业人士来做，他可以理解、阅读和改变程序。因为他们熟悉机床刀具，一些有能力的，有技术的工程师通过一些编程训练就可以手工编程。然而，这项工作十分乏味、耗时。手工编程大多数情况下用于简单的点定位中。（2）计算机辅助编程计算机辅助编程有特殊的程序语言。它决定了工件的拐角、边缘、和表面上的相关点。程序语言是和计算机交流的一种方式。编程人员用这种语言描述加工零件，而由计算机将零件程序转化为数控机床的执行指令。一些有多种特征和应用的语言都可以使用。第一种被运用的类似英语的语言叫做ATP（自动编程工具），它在十九世纪五十年代末开发出来了。这种语言仍然在点定位和仿型定位中得到了广泛的应用。计算机辅助

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