毕业设计（论文）英文资料翻译

Mechanical Design

NUMERICAL CONTROL

Numerical control 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 work part or job．When the job changes，the program of instructions is changed．The capability to change the program is what makes N／C suitable for low-and medium-volume production．It is much easier to write programs than to make major alterations of the processing equipment．

Number control lather main use to carry on a car to pare towards revolving body spare parts, the Tang pare, drill to pare, the Jiao pare, offend silk etc. process of work preface. General ability auto inside completion outside cylinder noodles, conic surface, surface of sphere, cylinder thread, slot and carry noodles etc. the slice of work preface pare to process.

The host is the topic that the number control lather and include a tool machine body, sign pillar, principal axis and enter etc. is to the organization machine parts. Number control equip, is number control tool machine of core, include hardware and correspond of software, used for an importation numeral turn of spare parts procedure, and completion importation information of saving, the transformation of data, put to repair operation and realization various control function. Drive to equip, he is number control the drive of organization of the tool machine performance parts, include a principal axis to drive unit and enter to the unit, principal axis electrical engineering and enter etc. to electrical engineering. He under the control that number control to equip pass electricity or electricity liquid servo system realization principal axis with enters give drive. When several enter to give allied move, can completion fixed position, straight line, process of flat surface curve and space curve. Assistance equips the index number control tool machine of some necessity of kit parts, in order to assurance number control tool machine of circulate, such as cool off, row scraps, lubricate, illuminate, monitor etc. It include a liquid to press friendly move equip, row scraps equip, exchange work set, number control to turn Taiwan and number control cent degree head. Plait distance and other subsidiary equipments, can use to carry on the procedure of spare parts to draw up outside machine, saving.

Modern number control lather to all have X, Z two stalk of allied move function, knife position and point of a knife arc radius of compensate function, and process fix circulation function.

The number control the structure of lather

1. The number control a lather brief introduction

The number control constitute of lather: Number control system, bed body, principal axis and enter to the system, turn round a knife, operation front-panel and assistance system etc..

 (1) The economy number control lather: Adoption step enter electric motor and list slice machine to common the car of the lather pare into to the system carry on reformation behind formation of the simple number control lather. The cost is lower, automation degree and function be all more bad, the car pare to process accuracy also not high, be applicable to request not high of turn round type spare parts of the car pare to process.

The economy number control lather

(2) Common number control lather: Pare to process a request to carry on the structure according to the car specialized design, equipment in general use number control system but formation of number control lather. Number control system function strong, automation degree with process accuracy also more Ago, be applicable to general turn round type spare parts of the car pare to process. This kind of number control lather can control 2 sit a mark stalk in the meantime, namely x stalk and z stalk.

Common number control lather

(3)the car pare to process center: At common number control the foundation of lather up, increment C stalk and motive head, more high class of the tool machine still take a knife database, can control X, Z and C 3 sit mark stalk, allied move control stalk can BE(X, Z),(X, C) or(Z, C).Because increment C stalk and Xian pare a motive head, this kind of number control process of lather function consumedly strengthen, in addition to carry on general the car pare, also can carry on path to pare with stalk toward the Xian, the curved face Xian pare, the center line don't turn round in the spare parts center of bore and path pare toward the drill of bore etc. process.

2. The liquid press card dish and liquid to press a tail

The liquid press card dish is number control a car to pare to process clip tight work piece of importance enclosure, rightness general turn round type spare parts can adoption common the liquid press card dish; To the spare parts be clip hold the part isn't the spare parts of cylinder form, demand adoption appropriation card dish; With the stick anticipate direct process spare parts demand adoption spring coil card dish.

To stalk to the size and the path is to the specific value bigger spare parts of size, demand adoption install press a tail in the liquid up of live top carry on prop up to the spare parts end tip, then can assurance carry on to the spare parts exactitude of process. The tail has a common liquid to press tail and programmable liquid to press a tail.

3. The number control the knife of lather

Number control lather can equipment two kinds of knife:

(1) Appropriation knife from lather produce manufacturer oneself development, haft for use is also appropriation of. This kind of the advantage be that the manufacturing cost is low, but lack in general use.

(2)in general use knife according to certain in general use standard(like VDI, Germany engineer's association) but produce of knife, number control lather production manufacturer can according to number control the function of lather request to carry on a choice allocation.

In general use knife

4. The Xian pare a motive head

Number control lather knife top to install Xian after pare the motive head can consumedly expand number to control process of lather ability. Such as :Make use of the Xian pare a motive head to carry on stalk to drill a hole to pare stalk toward the slot with Xian.

The N／C system consists of the following components：data input，the tape reader with the control unit，feedback devices，and the metal—cutting machine tool or other type of N／C equipment．

Data input，also called “man—to—control link”，may be provided to the machine tool manually，or entirely by automatic means．Manual methods when used as the sole source of input data are restricted to a relatively small number of inputs．Examples of manually operated devices are keyboard dials，pushbuttons，switches，or thumbwheel selectors．These are located on a console near the machine．Dials ale analog devices usually connected to a syn-chro-type resolver or potentiometer．In most cases，pushbuttons，switches，and other similar types of selectors aye digital input devices．Manual input requires that the operator set the controls for each operation．It is a slow and tedious process and is seldom justified except in elementary machining applications or in special cases．

In practically all cases，information is automatically supplied to the control unit and the machine tool by cards，punched tapes，or by magnetic tape．Eight—channel punched paper tape is the most commonly used form of data input for conventional N／C systems．The coded instructions on the tape consist of sections of punched holes called blocks．Each block represents a machine function，a machining operation，or a combination of the two．The entire N／C program on a tape is made up of an accumulation of these successive data blocks．Programs resulting in long tapes all wound on reels like motion-picture film．Programs on relatively short tapes may be continuously repeated by joining the two ends of the tape to form a loop．Once installed，the tape is used again and again without further handling．In this case，the operator simply loads and unloads the parts．Punched tapes ale prepared on type writers with special tape—punching attachments or in tape punching units connected directly to a computer system．Tape production is rarely error-free．Errors may be initially caused by the part programmer，in card punching or compilation，or as a result of physical damage to the tape during handling，etc．Several trial runs are often necessary to remove all errors and produce an acceptable working tape．

While the data on the tape is fed automatically，the actual programming steps ale done manually．Before the coded tape may be prepared，the programmer，often working with a planner or a process engineer, must select the appropriate N／C machine tool，determine the kind of material to be machined，calculate the speeds and feeds，and decide upon the type of tooling needed. The dimensions on the part print are closely examined to determine a suitable zero reference point from which to start the program．A program manuscript is then written which gives coded numerical instructions describing the sequence of operations that the machine tool is required to follow to cut the part to the drawing specifications．

The control unit receives and stores all coded data until a complete block of information has been accumulated．It then interprets the coded instruction and directs the machine tool through the required motions．

The function of the control unit may be better understood by comparing it to the action of a dial telephone，where，as each digit is dialed，it is stored．When the entire number has been dialed，the equipment becomes activated and the call is completed．

Silicon photo diodes，located in the tape reader head on the control unit，detect light as it passes through the holes in the moving tape．The light beams are converted to electrical energy，which is amplified to further strengthen the signal．The signals are then sent to registers in the control unit, where actuation signals are relayed to the machine tool drives．

Some photoelectric devices are capable of reading at rates up to 1000 characters per second．High reading rates are necessary to maintain continuous machine—tool motion；otherwise dwell marks may be generated by the cutter on the part during contouring operations．The reading device must be capable of reading data blocks at a rate faster than the control system can process the data．

A feedback device is a safeguard used on some N／C installations to constantly compensate for errors between the commanded position and the actual location of the moving slides of the machine tool．An N／C machine equipped with this kind of a direct feedback checking device has what is known as a closed-loop system．Positioning control is accomplished by a sensor which，during the actual operation，records the position of the slides and relays this information back to the control unit．Signals thus received ale compared to input signals on the tape，and any discrepancy between them is automatically rectified．

In an alternative system，called an open—loop system，the machine is positioned solely by stepping motor drives in response to commands by a controllers．There are three basic types of NC motions, as follows:

Point-to-point or Positional Control In point-to-point control the machine tool elements (tools, table, etc.) are moved to programmed locations and the machining operations performed after the motions are completed. The path or speed of movement between locations is unimportant; only the coordinates of the end points of the motions are accurately controlled. This type of control is suitable for drill presses and some boring machines, where drilling, tapping, or boring operations must be performed at various locations on the work piece. Straight-Line or Linear Control Straight-Line control systems are able to move the cutting tool parallel to one of the major axes of the machine tool at a controlled rate suitable for machining. It is normally only possible to move in one direction at a time, so angular cuts on the work piece are not possible, consequently, for milling machines, only rectangular configurations can be machined or for lathes only surfaces parallel or perpendicular to the spindle axis can be machined. This type of controlled motion is often referred to as linear control or a half-axis of control. Machines with this form of control are also capable of point-to-point control.

Continuous Path or Contouring Control In continuous path control the motions of two or more of the machine axes are controlled simultaneously, so that the position and velocity of the can be tool are changed continuously. In this way curves and surfaces can be machined at a controlled feed rate. It is the function of the interpolator in the controller to determine the increments of the individual controlled axes of the machines necessary to produce the desired motion. This type of control is referred to as continuous control or a full axis of control.

Some terminology concerning controlled motions for NC machines has been introduced. For example, some machines are referred to as four-or five-or even six-axis machines. For a vertical milling machine three axes of control are fairly obvious, these being the usual X, Y, Z coordinate directions. A fourth or fifth axis of control would imply some form of rotary table to index the work piece or possibly to provide angular motion of the work head. Thus, in NC terminology an axis of control is any controlled motion of the machine elements (spindles, tables, etc). A further complication is use of the term half-axis of control; for example, many milling machines are referred to as 2.5-axis machine. This means that continuous control is possible for two motions (axes) and only linear control is possible for the third axis. Applied to vertical milling machines, 2.5axis control means contouring in the X, Y plane and linear motion only in the Z direction. With these machines three-dimensional objects have to be machined with water lines around the surface at different heights. With an alternative terminology the same machine could be called a 2CL machine (C for continuous, L for linear control). Thus, a milling machine with continuous control in the X, Y, Z directions could be termed be a three-axis machine or a 3c machine, similarly, lathes is usually two axis or 2C machines. The degree of work precision depends almost entirely upon the accuracy of the lead screw and the rigidity of the machine structure．With this system．there is no self-correcting action or feedback of information to the control unit．In the event of an unexpected malfunction，the control unit continues to put out pulses of electrical current．If，for example，the table on a N／C milling machine were suddenly to become overloaded，no response would be sent back to the controller．Because stepping motors are not sensitive to load variations，many N／C systems are designed to permit the motors to stall when the resisting torque exceeds the motor torque．Other systems are in use，however，which in spite of the possibility of damage to the machine structure or to the mechanical system，ale designed with special high—torque stepping motors．In this case，the motors have sufficient capacity to “overpower’’ the system in the event of almost any contingency．

数控

数控是可编程自动化技术的一种形式，通过数字、字母和其他符号来控制加工设备。数字、字母和符号用适当的格式编码为一个特定工件定义指令程序。当工件改变时，指令程序就改变。这种改变程序的能力使数控适合于中、小批量生产，写一段新程序远比对加工设备做大的改动容易得多。

数控车床主要用来对旋转体零件进行车削、镗削、钻削、铰削、攻丝等工序的加工。一般能自动完成内外圆柱面、圆锥面、球面、圆柱螺纹、槽及端面等工序的切削加工。

主机是数控车床的主题，包括机床身、立柱、主轴、进给机构等机械部件。数控装置，是数控机床的核心，包括硬件以及相应的软件，用于输入数字化的零件程序，并完成输入信息的存储、数据的变换、插补运算以及实现各种控制功能。驱动装置，他是数控机床执行机构的驱动部件，包括主轴驱动单元、进给单元、主轴电机及进给电机等。他在数控装置的控制下通过电气或电液伺服系统实现主轴和进给驱动。当几个进给联动时，可以完成定位、直线、平面曲线和空间曲线的加工。辅助装置，指数控机床的一些必要的配套部件，用以保证数控机床的运行，如冷却、排屑、润滑、照明、监测等。它包括液压和气动装置、排屑装置、交换工作台、数控转台和数控分度头。编程及其他附属设备，可用来在机外进行零件的程序编制、存储等。

现代数控车床都具有X、Z两轴的联动功能、刀具位置和刀尖圆弧半径的补偿功能、以及加工固定循环功能。

数控车床的结构

1.数控车床简介

数控车床的组成：数控系统、床身、主轴、进给系统、回转刀架、操作面板和辅助系统等。

(1)经济型数控车床：采用步进电动机和单片机对普通车床的车削进给系统进行改造后形成的简易型数控车床。成本较低，自动化程度和功能都比较差，车削加工精度也不高，适用于要求不高的回转类零件的车削加工。

经济型数控车床

(2)普通数控车床：根据车削加工要求在结构上进行专门设计，配备通用数控系统而形成的数控车床。数控系统功能强，自动化程度和加工精度也比较高，适用于一般回转类零件的车削加工。这种数控车床可同时控制两个坐标轴，即x轴和z轴。

普通数控车床

(3)车削加工中心：在普通数控车床的基础上，增加了C轴和动力头，更高级的机床还带有刀库，可控制X、Z和C三个坐标轴，联动控制轴可以是(X、Z)、(X、C)或(Z、C)。由于增加了C轴和铣削动力头，这种数控车床的加工功能大大增强，除可以进行一般车削外，还可以进行径向和轴向铣削、曲面铣削、中心线不在零件回转中心的孔和径向孔的钻削等加工。

2.液压卡盘和液压尾架

液压卡盘是数控车削加工时夹紧工件的重要附件，对一般回转类零件可采用普通液压卡盘；对零件被夹持部位不是圆柱形的零件，则需要采用专用卡盘；用棒料直接加工零件时需要采用弹簧卡盘。

对轴向尺寸和径向尺寸的比值较大的零件，需要采用安装在液压尾架上的活顶尖对零件尾端进行支撑，才能保证对零件进行正确的加工。尾架有普通液压尾架和可编程液压尾架。

3.数控车床的刀架

数控车床可以配备两种刀架：

(1)专用刀架 由车床生产厂商自己开发，所使用的刀柄也是专用的。这种刀架的优点是制造成本低，但缺乏通用性。

(2)通用刀架 根据一定的通用标准(如VDI，德国工程师协会)而生产的刀架，数控车床生产厂商可以根据数控车床的功能要求进行选择配置。

4.铣削动力头

数控车床刀架上安装铣削动力头后可以大大扩展数控车床的加工能力。如：利用铣削动力头进行轴向钻孔和铣削轴向槽。

数控系统由下列组件组成：数据输入装置，带控制单元的磁带阅读机，反馈装置和切削机床或其他形式的数控设备。

数据输人装置，也称“人机联系装置”，可用人工或全自动方法向机床提供数据。人工方法作为输人数据唯一方法时，只限于少量输入。人工输入装置有键盘，拨号盘，按钮，开关或拨轮选择开关，这些都位于机床附近的一个控制台上。拨号盘通常连到一个同步解析器或电位计的模拟装置上。在大多数情况下，按钮、开关和其他类似的旋钮是数据输入元件。人工输入需要操作者控制每个操作，这是一个既慢又单调的过程，除了简单加工场合或特殊情况，已很少使用。

几乎所有情况下，信息都是通过卡片、穿孔纸带或磁带自动提供给控制单元。在传统的数控系统中，八信道穿孔纸带是最常用的数据输入形式，纸带上的编码指令由一系列称为程序块的穿孔组成。每一个程序块代表一种加工功能、一种操作或两者的组合。纸带上的整个数控程序由这些连续数据单元连接而成。带有程序的长带子像电影胶片一样绕在盘子上，相对较短的带子上的程序可通过将纸带两端连接形成一个循环而连续不断地重复使用。带子一旦安装好，就可反复使用而无需进一步处理。此时，操作者只是简单地上、下工件。穿孔纸带是在带有特制穿孔附件的打字机或直接连到计算机上的纸带穿孔装置上做成的。纸带制造很少不出错，错误可能由编程、卡片穿孔或编码、纸带穿孔时的物理损害等形成。通常，必须要试走几次来排除错误，才能得到一个可用的工作纸带。

虽然纸带上的数据是自动进给的，但实际编程却是手工完成的，在编码纸带做好前，编程者经常要和一个计划人员或工艺工程师一起工作，选择合适的数控机床，决定加工材料，计算切削速度和进给速度，决定所需刀具类型，仔细阅读零件图上尺寸，定下合适的程序开始的零参考点，然后写出程序清单，其上记载有描述加工顺序的编码数控指令，机床按顺序加工工件到图样要求。控制单元接受和储存编码数据，直至形成一个完整的信息程序块，然后解释数控指令，并引导机床得到所需运动。

为更好理解控制单元的作用，可将它与拨号电话进行比较，即每拨一个数字，就储存一个，当整个数字拨好后，电话就被激活，也就完成了呼叫。

装在控制单元里的纸带阅读机，通过其内的硅光二极管，检测到穿过移动纸带上的孔漏过的光线，将光束转变成电能，并通过放大来进一步加强信号，然后将信号送到控制单元里的寄存器，由它将动作信号传到机床驱动装置。

有些光电装置能以高达每秒1000个字节的速度阅读，这对保持机床连续动作是必须的，否则，在轮廓加工时，刀具可能在工件上产生划痕。阅读装置必须要能以比控制系统处理数据更快的速度来阅读数据程序块。

反馈装置是用在一些数控设备上的安全装置，它可连续补偿控制位置与机床运动滑台的实际位置之间的误差。装有这种直接反馈检查装置的数控机床有一个闭环系统装置。位置控制通过传感器实现，在实际工作时，记录下滑台的位置，并将这些信息送回控制单元。接受到的信号与纸带输入的信号相比较，它们之间的任何偏差都可得到纠正。

在另一个称为开环的系统中，机床仅由响应控制器命令的步进电动机驱动定位，工件的精度几乎完全取决于丝杠的精度和机床结构的刚度。有几个理由可以说明步进电机是一个自动化申请的非常有用的驱动装置。对于一件事物，它被不连续直流电压脉冲驱使,是来自数传计算机和其他的自动化的非常方便的输出控制系统。当多数是索引或其他的自动化申请所必备者的时候，步进电机对运行一个精确的有角进步也是理想的。因为控制系统不需要监听就提供特定的输出指令而且期待系统适当地反应的公开- 环操作造成一个回应环，步进电机是理想的。 一些工业的机械手使用高抬腿运步的马乘汽车驾驶员，而且步进电机是有用的在数字受约束的工作母机中。 这些申请的大部分是公开- 环 ,但是雇用回应环检测受到驱策的成份位置是可能的。 环的一个分析者把真实的位置与需要的位置作比较，而且不同是考虑过的错误。 那然后驾驶员能发行对步进电机的电脉冲，直到错误被减少对准零位。在这个系统中，没有信息反馈到控制单元的自矫正过程。出现误动作时，控制单元继续发出电脉冲。比如，一台数控铣床的工作台突然过载，阻力矩超过电机转矩时，将没有响应信号送回到控制器。因为，步进电机对载荷变化不敏感，所以许多数控系统设计允许电机停转。然而，尽管有可能损坏机床结构或机械传动系统，也有使用带有特高转矩步进电机的其他系统，此时，电动机有足够能力来应付系统中任何偶然事故。