數(shù)控機(jī)床外文翻譯

1、<p>　　本科生畢業(yè)設(shè)計(jì)（論文）外文翻譯</p><p>　　外文題目：Numerically Controlled (NC) Machines</p><p><b>　　譯文題目：數(shù)控機(jī)床</b></p><p>　　學(xué) 生 姓 名： 張 龍 </p><

2、;p>　　專(zhuān) 業(yè)： 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 </p><p>　　指導(dǎo)教師姓名： 張 凱 </p><p>　　評(píng) 閱 日 期： </p><p>　　Num

3、erically Controlled (NC) Machines</p><p>　　With automatics, programming is expensive and can be justified only for long production runs. However, with machines incorporating feedback control, programs can be

4、 provided in the form of punched tapes or punched cards, which are relatively inexpensive to produce compared with disc and drum cams. These machines are known as numerically controlled (NC) machines and can be used econ

5、omically in small-batch production.</p><p>　　As the name implies, numerical control involves control on the basis of numerical information that specifies the relative position of the tool and workpiece. From

6、 the block diagram for a machine-tool control system in Fig. 12 it can be seen that two essential elements are added to an otherwise standard machine.</p><p>　　The first added element is a means of driving t

7、he machine table or toolholder by a servomotor, and hence the motion of the tool or workpiece depends on the signal passed to the servomotor. The second added element is a transducer that continuously monitors the positi

8、on of the tool or workpiece. The signal from the transducer is compared with that obtained from the tape, and any difference (or error) is converted to analog form, amplified, and used to drive the servomotor until the t

9、ool or workpi</p><p>　　Fig. 12: Feedback loop for one axis of a machine-tool control system</p><p>　　There are two basic types of NC systems: the point-to-point, or positioning, system and the c

10、ontinuous-path, or contouring, system. The point-to-point system would be applied, for example, to a vertical-drilling machine. If control of the two horizontal-motion axes of the table supporting the workpiece is arrang

11、ed, the machine can be programmed to locate and then drill a specified pattern of holes. In the point-to-point system the path of the tool relative to the workpiece between holes is not i</p><p>　　With conti

12、nuous-path, or contouring, systems the position of the tool relative to the workpiece is specified by a series of coordinates, and the control system is designed to follow a path between these points by interpolation. So

13、me machines follow a straight-line path (linear interpolation); others follow a curved path (circular or parabolic interpolation).</p><p>　　Numerical control can be applied to motions along or about any axis

14、,· but two or three-axis control systems are the most common. In general, vertical-milling machines and lathes utilize continuous-path, or contouring control. Vertical-drilling machines jig borers, and small milling

15、 machines often use positional control.</p><p>　　One sophisticated form of NC machine is known as the machining center. This machine is generally a vertical-milling machine with several axes of control and w

16、ith automatic tool-changing facilities. The tools are usually held in a rotary magazine, and tool changes are commanded by the punched tape. Thus, with a machining center a complicated workpiece can be completely machine

17、d on all faces except the base through a combination of milling, drilling, boring, facing, reaming, and tapping operations</p><p>　　A further refinement of numerical control is adaptive control. This type of

18、 system can adapt itself to the prevailing circumstances. These circumstances are measured by the system itself and might include the power required for the machining operation, the wear of the cutting tool or grinding w

19、heel, the forces generated, or the onset of chatter or instability. The system ideally would be designed for automatic adjustment of the feed, speed, or tool position to produce components at minimum cost </p><

20、;p>　　A relatively simple adaptive control system would automatically vary the cutting speed and feed in such a way as to maximize metal-removal rates without exceeding predetermined cutting forces and power consumptio

21、n. Systems of this type are relatively inexpensive and can machine under near-optimum conditions.</p><p><b>　　數(shù)控機(jī)床</b></p><p>　　伴隨著自動(dòng)化產(chǎn)生，只有在長(zhǎng)期的生產(chǎn)運(yùn)行中，編程的價(jià)格很昂貴，同時(shí)又是合理的。然而，機(jī)器在反饋系統(tǒng)的控制下，程

22、序能以沖制墊圈或穿孔卡片的形式提供，它能相對(duì)便宜生產(chǎn)比較裝置與磁鼓容量。這些機(jī)器被稱(chēng)為數(shù)字控制（數(shù)控）機(jī)床，可用于經(jīng)濟(jì)的小批量生產(chǎn)。</p><p>　　正如名字所暗示的，數(shù)值控制包括在指定相對(duì)位置的工具和工件的數(shù)值信息的基礎(chǔ)上的控制。從一個(gè)機(jī)床控制系統(tǒng)框圖（如圖12）可以看出，基本元素添加到一個(gè)標(biāo)準(zhǔn)機(jī)上。</p><p>　　第一個(gè)添加的元素是指驅(qū)動(dòng)機(jī)或由伺服電機(jī)控制的刀柄，因此，運(yùn)動(dòng)的

23、工具或工件取決于傳遞給伺服電機(jī)的信號(hào)。第二個(gè)添加元素是一個(gè)傳感器，連續(xù)監(jiān)測(cè)工具或工件的位置。來(lái)自傳感器的信號(hào)與來(lái)自磁盤(pán)的信號(hào)相比較，和任何區(qū)別（或錯(cuò)誤）轉(zhuǎn)換為模擬形式，放大，并用于驅(qū)動(dòng)伺服電機(jī)，直到工具或工件的位置符合規(guī)定位置磁帶上的信息。</p><p>　　圖12：機(jī)床一個(gè)軸的反饋環(huán)路控制系統(tǒng)</p><p>　　有一個(gè)基本類(lèi)型的數(shù)控系統(tǒng)：點(diǎn)對(duì)點(diǎn)，或定位，系統(tǒng)和連續(xù)軌跡，或輪廓系統(tǒng)。點(diǎn)

24、對(duì)點(diǎn)系統(tǒng)應(yīng)用，例如，對(duì)一個(gè)垂直鉆井機(jī)。如果兩個(gè)水平軸的控制支持工件的安排，該機(jī)可以編程，找到并鉆一個(gè)指定的模式孔。在點(diǎn)對(duì)點(diǎn)系統(tǒng)，工具的路徑相對(duì)于兩孔之間工件的路徑是不重要的，只要每個(gè)運(yùn)動(dòng)的終點(diǎn)坐標(biāo)被指定。連續(xù)軌跡系統(tǒng)應(yīng)用，例如，一個(gè)需要端銑刀形狀復(fù)雜的縱面車(chē)鉤機(jī)，如凸輪或口小型的工件。當(dāng)工件被加工時(shí)，在連續(xù)路徑系統(tǒng)中，相對(duì)于工件工具的位置一定是連續(xù)控制的。</p><p>　　在連續(xù)路徑或輪廓中，相對(duì)于工件系統(tǒng)工

25、具的位置是由一系列坐標(biāo)指定的，控制系統(tǒng)被設(shè)計(jì)來(lái)遵循的路徑點(diǎn)之間的插值。有些機(jī)器遵循直線路徑（線性插值法）；其他的沿著一條曲線（圓或拋物線插值法）。</p><p>　　數(shù)值控制能被應(yīng)用到運(yùn)動(dòng)或任何軸，但兩或三個(gè)軸控制系統(tǒng)是最常見(jiàn)的。一般來(lái)說(shuō)，縱面車(chē)鉤機(jī)及車(chē)床利用連續(xù)路徑或輪廓控制。垂直鉆井機(jī)座標(biāo)鏜床，小型銑床經(jīng)常使用位置控制。</p><p>　　一個(gè)復(fù)雜的形式的數(shù)控機(jī)床被稱(chēng)為加工中心。這

26、種機(jī)器一般是縱面車(chē)鉤機(jī)多軸控制和自動(dòng)控制換刀機(jī)構(gòu)。該工具通常被放在旋轉(zhuǎn)的箱體中，工具的變化是由沖制墊圈控制的。因此，一個(gè)加工中心完全可以加工一個(gè)復(fù)雜工件的所有面除了底座要結(jié)合銑，鉆，鏜，擴(kuò)孔，攻絲操作。這種類(lèi)型的系統(tǒng)，因此是最適合批量生產(chǎn)的主要組成部分。進(jìn)一步完善數(shù)值控制自調(diào)控制。這種類(lèi)型的系統(tǒng)可以適應(yīng)當(dāng)時(shí)的情況。這些情況是衡量系統(tǒng)本身和所需的加工操作的動(dòng)力，磨損的刀具或砂輪，產(chǎn)生的動(dòng)力，或發(fā)生顫振或不穩(wěn)定。這系統(tǒng)最好備設(shè)計(jì)成會(huì)自動(dòng)調(diào)整

27、的進(jìn)給箱，轉(zhuǎn)速，刀具位置以最小的成本和規(guī)定的公差內(nèi)生產(chǎn)零件。這樣一個(gè)系統(tǒng)將是非常昂貴的，尚未發(fā)現(xiàn)有廣泛的應(yīng)用。</p><p>　　一個(gè)相對(duì)簡(jiǎn)單的自調(diào)控制系統(tǒng)會(huì)自動(dòng)改變切削速度和進(jìn)給以這種方式最大限度地控制金屬去除率不超過(guò)預(yù)定的切削力和功率消耗。近最佳條件下，這種類(lèi)型的系統(tǒng)是相對(duì)便宜。</p><p>　　注：圖12中：Tape reader 紙帶輸入機(jī)</p&

28、gt;<p>　　Comparator 坐標(biāo)測(cè)量?jī)x</p><p>　　Error signal 誤差信號(hào)</p><p>　　Transducer 變換器 換能器</p><p>　　Digital analog converter 數(shù)字模擬轉(zhuǎn)換器</p><

29、;p>　　Worktable 工作臺(tái)</p><p>　　Amplifier 放大器</p><p>　　Servomotor 伺服電動(dòng)機(jī)</p><p>　　Lead screw 導(dǎo)螺旋</p><p>　　英文翻譯指導(dǎo)教師評(píng)閱意見(jiàn)