第一篇：中英文对照文章8（共）
剃须心得： 有钱不必花在刀刃上
A Penny Shaved Is A Penny Earned
For years, I've felt like a sap whenever I bought razors.很多年来，每当我买剃须刀时都觉得自己像个傻瓜。
It killed me to spend $2.50 to $3 a blade for my Gillette Mach 3.Yet the few times when I used cheap disposable razors, it was like shaving with a file.为我的吉列锋速3（Gillette Mach 3）买一个刀片要花2.50美元到3美元，这让我心疼不已。但有几次我用便宜的一次性剃须刀时，感觉就像在用锉刀刮胡子。
Finally, a couple of weeks ago, I bought a serviceable store-brand razor that costs about half the price of the premier brands.Jon Protas for The Wall Street Journal
吉列锋速3是好剃须刀，但刀片的价钱真不便宜最终，几星期前，我买了一把商店自有品牌的剃须刀，这把剃须刀也还好用，而且价格只有名牌剃须刀的一半左右。
It shouldn't have come to this.I've used Gillette razors for decades, and I like them.The rub is the cost.In my book, a fair price for refills would be about a buck.事情不应该变成这样。我已经用了几十年吉列剃须刀了，而且我喜欢用它。问题出在价格上。在我看来，刀片的合理价格应该约为1美元。
I'm a believer in markets, but it doesn't seem like the razor-blade market gives me what I want.Instead of competing on price, Gillette and Schick largely seem to be engaged in a silly arms race to improve a product that already works perfectly well.Two blades, three blades, four blades--when will it stop? 我是一个信奉市场的人，但剃须刀刀片市场看来并没有给出我想要的结果。吉列（Gillette）和舒适（Schick）并没有在价格上进行竞争，而更像是投入了一场愚蠢的军备竞赛，以改进一种本来已经很完善的产品。双刀片、三刀片、四刀片──什么时候才是个头？
Not anytime soon, apparently.Schick will soon launch its own five-blade razor, and says that prices for it should be 10% to 20% above the Quattro, its four-blade razor that was introduced in 2003.显然，这种趋势短期内不会停止。舒适公司很快将推出它的五刀片剃须刀，并称该产品的价格将比其2003年推出的四刀片剃须刀“创4纪”（Quattro）高10%至20%。
Gillette, a unit of Procter & Gamble, got there first.Its Fusion Power MVP--an early version of which went on sale in 2006--has five spring-mounted blades and battery-powered micropulses to reduce friction 'so you barely feel the blades.' The
Gillette Web site has a video of a mechanic with a giant razor blade on a car lift.宝洁公司（Procter & Gamble）旗下的吉列公司是率先推出五刀片剃须刀的生产商。吉列的Fusion Power MVP──这款剃须刀的早期型号于2006年上市──带有五个弹簧式刀片和电动微脉冲以减少摩擦，“因此您几乎感觉不到刀片”。吉列公司的网站上有一段视频，视频中，一位拿着巨型剃须刀刀片的机械师站在一架汽车升降机上。
Razor makers, I have news for you.A razor is not a sports car.It won't make us feel young again or turn women's heads.We don't like shaving, and no matter what you do, we never will.All we want is a razor that will do the job without nicking us, either literally or figuratively.剃须刀生产商，有件事我要告诉你们。剃须刀不是跑车。它不会让我们感觉重返青春，也不会引来女性的顾盼。我们不喜欢刮胡子，不管你们怎么做，我们都不会喜欢。我们想要的只是一把不会刮伤脸，也不会让荷包挨宰的剃须刀。
But Gillette and Schick have a different view.Gillette is constantly doing research and development to create the perfect shave, says Mike Norton, a spokesman.'It's not the number of blades, it's the science behind the blades that gives you a better shave.' 但吉列公司和舒适公司有不同的观点。吉列公司的发言人迈克•诺顿（Mike Norton）称，吉列公司一直致力于研发能带来完美剃须体验的剃须刀。“关键不是刀片的数量，而是刀片背后带给您更佳剃须体验的科技。”
Jackie Burwitz of Energizer Holdings, which owns Schick, says, 'If you look at the sales data, consumers are willing to pay up for a better-performing razor.' 舒适公司的母公司，劲量控股公司（Energizer Holdings）的杰基•布尔维茨（Jackie Burwitz）说：“如果你考察销售数据，就会发现消费者愿意为性能更好的剃须刀多掏钱。”
There you have it.There's more money to be made developing fancier and fancier razors than in keeping the same razors and engaging in a price war.In other words, we American males have only ourselves to blame for the five-blade razor.现在你明白了吧。研发越来越高档的剃须刀比守着老款式剃须刀打价格战能赚到更多钱。换句话说，面对五刀片剃须刀，我们美国男人只能怨自己。
Over the years, I've compensated for the rising prices of razor blades by using less of them.Whereas I once might have changed blades every week or so, I now go two or three weeks before popping in a new one.这些年来，我应对剃须刀刀片涨价的方法就是少用它们。我曾经几乎每周都更换刀片，而我现在两至三个星期才更换新刀片。
A colleague of mine is married to a thrifty Frenchman who waits at least two months before changing razor blades.He has gone as long as six months.When he does
change blades, it feels 'like a warm knife through butter,' says Jean-Philippe Masson, 36 years old.'If you changed every week, you would not appreciate that pleasure.' 我的一位同事嫁给了一个节俭的法国人，他至少等两个月才换一次剃须刀刀片，最长六个月才换一次刀片。36岁的让-菲利普•马松（Jean-Philippe Masson）说，当他换完刀片后，刮胡子的感觉“就像热刀子切开黄油一般顺畅”。“如果你每周都换刀片，就享受不到这种乐趣了。”
That's the French way.The American way, of course, rarely involves denying ourselves something.Instead, we look for a way to get it cheaper.这是法国人的处理方式。当然，我们美国人很少有好东西舍不得用，而是会寻找让它更便宜的方法。
Maybe that's why there's a thriving market out there for after-market razors.可能这就是剃须刀刀片市场如此兴旺的原因。
There are people still selling blades for Gillette Trac II, the two-blade razor I used as a young man.A Web site advertised a 100-pack of after-market refills for $49.99.Alas, I haven't owned a Trac II for many years.有人仍在卖吉列Trac II的刀片，我年轻时用过这种双刀片剃须刀。一个网站上刊登了一种100片装Trac II刀片的广告，其售价为49.99美元。唉，可惜我已经有许多年没用过Trac II了。
Instead, I went to my local CVS pharmacy, where the chain was pitching its 'three-blade shaving system.' I paid $12.50 for a razor and 10 blades, bringing my per-blade cost to $1.25.无奈之下，我去了本地的CVS药店（CVS pharmacy），这家连锁店正在推销其“三刀片剃须套装”。我花12.50美元买了一把剃须刀和10个刀片，这样每个刀片的价格就降到了1.25美元。
I've been trying out the CVS razor for the past couple of weeks.It was just as comfortable as the three-blade Gillette I've used for several years.过去几周我一直在试用CVS剃须刀。它用起来和我已经用了几年的三刀片吉列剃须刀一样舒适。
The Gillette might have given me a slightly closer shave than the CVS razor.I really can't say for sure.I can't tell the difference between a great shave and good one.But I can tell the difference between paying $2.50 and $1.25.吉列剃须刀的剃须感觉可能比CVS剃须刀稍微贴合一些，但我真的说不准。我说不出上佳的剃须体验和良好的剃须体验有何区别。但我说得出花2.50美元和花1.25美元的区别。
To be fair to Gillette, I agreed to try out its latest, greatest razor.So Gillette sent me a Fusion ProGlide Power razor, a five-blade razor that hits the market in June.It will have a suggested retail price of $12.99 for a razor and two cartridges.A four-pack of refills will cost $17.99.为了对吉列公平，我同意试用其最新最好的剃须刀。于是，吉列公司寄给我一款Fusion ProGlide Power剃须刀，这是一种将于6月上市的五刀片剃须刀。这款剃须刀的建议零售价为12.99美元，包括一把剃须刀和两个备
用刀头。含四个备用刀头的套装售价为17.99美元。
I used the new razor over the weekend before sending it back to Gillette.It was a closer shave.But when I finished, the smooth face I saw peering back in the mirror was still my own, not George Clooney's.And I'd still feel like a sap spending $4.50 each time I changed blades.周末用过这款新剃须刀后，我将它寄回给吉列公司，用它剃须的感觉的确更贴合。但当我刮完胡子后，我在镜子里看到的那张光滑面庞仍然是我的脸，而不是乔治•克鲁尼的，而当我每次为换刀片花4.5美元时，仍然感觉自己像个傻瓜。
So I'm sticking with the CVS razor.Until I find something cheaper.所以我会继续使用CVS的剃须刀，直到我找到更便宜的剃须刀为止。
2012世界末日预言网上整理。
第二篇：中英文对照文章⑥
If如果
If you can keep your head when all about you Are losing theirs and blaming it on you;
If you can trust yourself when all men doubt you, But make allowance for their doubting too;
If you can wait and not be tired by waiting,Or, being lied about,don't deal in lies,Or, being hated, don't give way to hating,And yet don't look too good, nor talk too wise;
If you can dreamand not make thoughts your aim;If you can meet with triumph and disaster
And treat those two impostors just the same;If you can bear to hear the truth you've spoken Twiseted by knaves to make a trap for fools,Or watch the things you gave your life to broken, And stoop and build 'em up with wornout tools;
If you can make one heap of all your winnings And risk it on one turn of pitch-and-toss,And lose, and start again at your beginnings And never breathe a word about your loss;
If you can force your heart and nerve and sinew To serve your turn long after they are gone, And so hold on when there is nothin in you
Except the Will which says to them:“Hold on!”;
If you can talk with crowds and keep your virtue, Or walk with Kings-nor lose the common touch;If neither foes nor loving friends can hurt you;If all men count with you, but none too much;If you can fill the unforgiving minute
With sixty second' worth of distance run-
Yours is the Earth and everything that's in it, Andyou'll be a Man my son!
如果所有人都失去理智，咒骂你，你仍能保持头脑情形；
如果所有人都怀疑你，你仍能坚信自己，让所有的怀疑动摇；
如果你要等待，不要因此厌烦，为人所骗，不要因此骗人，为人所恨，不要因此抱恨，不要太乐观，不要自以为是；
如果你是个追梦人——不要被梦主宰；
如果你是个爱思考的人——光想会达不到目标； 如果你遇到骄傲和挫折
把两者当骗子看待；
如果你能忍受，你曾讲过的事实
被恶棍扭曲，用于蒙骗傻子；
看着你用毕生去看护的东西被破坏，然后俯身，用破烂的工具把它修补；
如果在你赢得无数桂冠之后„
突遇颠峰下跌之险，失败过后，东山再起，不要抱怨你的失败；
如果你能迫使自己，在别人走后，长久坚守阵地，在你心中已空荡荡无一物‟
只有意志告诉你“坚持！”；
如果你与人交谈，能保持风度，伴王行走，能保持距离；
如果仇敌和好友都不害你；
如果所有人都指望你，却无人全心全意； 如果你花六十秒进行短程跑，填满那不可饶恕的一分钟—— 你就可以拥有一个世界，这个世界的一切都是你的，更重要的是，孩子，你是个顶天立地的人。
第三篇：中英文对照文章11（精选）
通用汽车在沪推出微型电动车EN-V
GM Shows Its EN-V in Shanghai
General Motors Co.introduced a pod-like electric vehicle in Shanghai this week, a vision for a car of the future to help solve urban-transportation problems such as congestion and pollution.通用汽车公司(General Motors Co.)本周在上海推出了一款豆荚状电动汽车，人们从中可以一窥未来能帮助缓解堵车和污染等城市交通问题的汽车会是什么样子。
The two-seater EN-V, or 'Electric Networked-Vehicle,' is a third the length of a regular car at 1.5 meters.It will be equipped with wireless communication and GPS-based navigation that will help it avoid accidents and pick the fastest routes based on real-time traffic conditions, GM says.这款名为EN-V的两座“电动联网概念车”只有1.5米长，仅为普通轿车长度的三分之一。通用汽车说，EN-V将配备无线通讯装置和GPS卫星导航系统，这些装置将帮助它避免交通事故，并根据实时交通状况选择行驶速度最快的交通线路。
The EN-V likely won't actually hit the roads for a long while yet-if ever.但EN-V真的上路行驶可能还要很长时间才能实现，如果会有这么一天的话。
GM has put forward a 20-year timeframe for the EN-V to catch on, and it may turn out to be more of a curiosity object like the Segway, GM's collaborator on the project.But if it works anywhere, it will likely work in China, which has no shortage of packed urban environments and swaths of consumers who have little or no history with traditional cars and may be more open to trying new concepts.通用汽车准备给EN-V 20年的时间来逐步被市场接受，而这款车最终有可能像通用的另一款微型车Segway一样，更多只是一种新奇的玩意儿。但如果EN-V真有用武之地的话，这个地方有可能是中国。中国不仅城市的停车位紧张，而且许多消费者都不曾或很少有过驾驶传统型轿车的经历，他们可能更乐于尝试新的概念车。
GM expects the EN-V, if put into production, to cost less than a small car but more than a moped.通用汽车预计，EN-V如果投产，其价格会在小型轿车和摩托车之间。
For now, with its future still unclear, the EN-V at least represents an important P.R.move for GM, which has been criticized for not thinking ahead.目前看来，虽然EN-V的市场前景仍不明朗，但推出这款车至少是通用汽车一个重要的公关举措，该公司一直被批评为缺乏前瞻性思维。
2012世界末日预言网上整理。
第四篇：中英文对照文章10
天涯网将中断与谷歌的多个合作项目
Tianya To Discontinue Working With Google On Several Projects
Tianya, an Internet company that runs one of China's most popular online forums, said Wednesday that it would discontinue working with Google Inc.(GOOG)on several projects in light of the company's decision to snub Chinese authorities and reroute its Chinese users to a Hong Kong Web site.互联网公司天涯网周三说，鉴于谷歌(Google Inc.)决定不再遵守中国有关部门的网络审查规定、把中国用户转到香港网站，天涯网将中断与谷歌的数个合作项目。天涯网运营着中国最受欢迎的在线论坛之一。
Xing Ming, chief executive of the company, which uses Google technology to power some of its site functions, said the company has begun implementing a plan to continue its operations without Google's help.天涯网首席执行长邢明说，该公司已经开始实施一项计划，将在没有谷歌的帮助下继续运营。天涯网使用谷歌技术来支持部分网站功能。
'Though Google left, we still need to continue offering our services to our customers and meet our clients requests,' Xing said.'There were many fields we were planning to cooperate on, such as online video, and though we just got a license to provide online video, Google has left.So we will run the video business by ourselves.' 邢明说，尽管谷歌离开了，我们仍需要继续向客户提供服务，满足客户的需求。我们有很多计划合作的领域，比如在线视频；尽管我们刚刚获得提供在线视频的许可，谷歌却离开了。所以，我们将独自运营视频业务。
In addition, Xing said Tianya has taken full control of Tianya Laiba, its social-networking service, and Tianya Wenda, a question-and-answer service, which were formerly operated with Google.此外，邢明说，天涯网已经做出决定，可能自己来运营社交服务“天涯来吧”和问答服务“天涯问答”。这两项业务现在是与谷歌一起运营的。
Google could not be immediately reached for comment, but has said it plans to fulfill its contractual obligations to partners, even after its move Tuesday to stop adhering to Chinese censorship regulations.记者暂时无法联系到谷歌相关人员发表置评。不过谷歌说，即使从周二开始不再遵守中国的审查规定，它计划履行对合作伙伴的合同义务。
The company now reroutes traffic to its Chinese domain address, Google.cn, to Google.com.hk, where it is hosting a service optimized for mainland Chinese users alongside its search site for Hong Kong users, but it's unclear how long authorities will allow that to continue.The move was seen by officials as deliberate defiance of Google's earlier agreements to follow China's Internet regulations.谷歌目前把中文网站Google.cn的用户转到了Google.com.hk。该网站提供对香港用户的搜索网站，同时还提供为大陆用户优化的服务，不过不清楚有关部门能允许这种局面持续多久。中国官员们认为此举是谷歌故意挑战此前有关同意遵守中国互联网规定的协议。
Tianya's decision comes after Hong Kong-based media company Tom Group Ltd.(TOCOF, 2383.HK)said it removed Google's search service from its Web portal in order to stay in
compliance with China's rules and regulations.在天涯网作出上述决定前，位于香港的媒体公司TOM集团(Tom Group Ltd.)说，把谷歌搜索服务从自己的门户网站上去除了，以便遵守中国的规定和条例。
Other Google partners who used Google's Chinese search engine, including mobile operator China Mobile Ltd.(CHL, 0941.HK)and Web portal Sina Corp.(SINA), will have to decide whether to continue using Google's services as well.其他使用谷歌中文搜索引擎的合作伙伴──包括手机运营商中国移动和门户网站新浪──将必须决定是否继续使用谷歌的服务。
2012世界末日预言
网上整理。
第五篇：机械专业英语文章中英文对照
英语原文
NUMERICAL CONTROL
Numerical control(N/C)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.There are two basic types of numerically controlled machine tools：point—to—point and continuous—path(also called contouring).Point—to—point machines use unsynchronized motors, with the result that the position of the machining head Can be assured only upon completion of a movement, or while only one motor is running.Machines of this type are principally used for straight—line cuts or for drilling or boring.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 are 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 and1
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 is one basic type of NC motions.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.The original N/C used the closed—loop system.Of the two systems, closed and open loop, closed loop is more accurate and, as a consequence, is generally more expensive.Initially, open—loop systems were used almost entirely for light-duty applications because of inherent power limitations previously associated with conventional electric stepping motors.Recent advances in the development of electro hydraulic stepping motors have led to increasingly heavier machine load applications.中文译文
数控技术
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。
数控机床有两种基本形式：点位控制和连续控制(也称为轮廓控制)。点位控制机床采用异步电动机,因此,主轴的定位只能通过完成一个运动或一个电动机的转动来实现。这种机床主要用于直线切削或钻孔、镗孔等场合。
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。
最初的数控系统采用开环系统。在开、闭环两种系统中,闭环更精确,一般说来更昂贵。起初,因为原先传统的步进电动机的功率限制,开环系统几乎全部用于轻加工场合,最近出现的电液步进电动机已越来越多地用于较重的加工领域。
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