Text a Machine Tools

Machine Tools are stationary power-driven machines. They are used when solid materials, especially metals, are being shaped or formed. Machine tools form the basis of modern industry and are usually used either directly or indirectly in the manufacture of machine and tool parts.

Machine tools may be classified under two main categories: conventional chip-making machine tools and unconventional machine tools. Conventional chip-making tools shape the workpiece cutting away the unwanted portion in the form of chips. Unconventional machine tools employ light, electrical, chemical, and ultrasonic energy; superheated gases; and high-energy particle beams when shaping the exotic materials and alloys.

Conventional Machine Tools

Lathe

A lathe, the oldest and most common type of turning machine, holds and rotates a workpiece shaping the material with a cutting tool. The tool may be moved parallel to or across the direction of rotation forming parts that have a cylindrical or conical shape or to cut threads.

Shaper and Planer

The shaper is used to produce flat surfaces. It uses a single-point tool and is comparatively slow. For this reason, the shaper is seldom found on a production line. It is, however, essential in tool rooms and job shops when a few identical parts are being made.

The planer is another machine which is the largest of the reciprocating machine tools. Like the shaper, the planer is used where identical, horizontal, or diagonal cuts are being produced.

Milling Machine

In a milling machine, a workpiece is cut by a circular device with a series of cutting edges on its circumference. The workpiece is held on a table which is feeding it against the cutter. The table has three possible movements: longitudinal, horizontal, and vertical; in some cases it can rotate.

Drilling and Boring Machines

Hole-making machine tools are used to drill a hole where none previously existed; to change a hole in accordance with some specification. There are different drilling machines: from hand drills to radial drilling machines and multispindle units. Boring is a process that increases holes previously drilled.

Grinders

Grinding is the removal of material by a rotating abrasive wheel. The wheel consists of many small particles of abrasive, connected together. Each particle acts as a miniature cutting tool. The process produces extremely smooth and accurate surfaces.

Cutting Tools and Fluids

Because cutting processes include high local stresses, frictions, and heat generation, cutting-tool material must combine strength, toughness, hardness, and wear resistance at high temperatures. These requirements are met, in different degrees, by such cutting-tool materials as carbon steels, stainless steels, high-speed steels, tungsten carbide, and diamonds and by such recently developed materials as ceramic, carbide ceramic, and aluminum oxide.

In many cutting operations fluids are used to cool and lubricate. Cooling reduces friction, decreasing the heat generation, increases tool life and helps to stabilize the size of the finished part.

Задания к тексту A:

I. Прочитайте и переведите следующие выражения:

stationary power-driven machines; the manufacture of machine and tool parts; the unwanted portion in the form of chips; light, electrical, chemical, and sonic energy; high-energy particle beams; a turning machine; a cutting tool; to be moved parallel to or across the direction of rotation; to cut threads; flat surfaces; a single-point tool; for this reason; a production line; the reciprocating machine tools; a milling machine; a series of cutting edges on its circumference; hole-making machine tools; in accordance with; multispindle units; an abrasive wheel; heat generation; cutting-tool materials; carbon steels; high-speed steels; tungsten carbide; carbide ceramic.

II. Найдите в предыдущем упражнении английские эквиваленты следующих русских выражений:

станок возвратно-поступательного действия; лишний материал в виде стружки; в соответствии с; луч из высокоэнергетических частиц; фрезерный станок; режущий инструмент; значительная выработка тепла; карбидная керамика; материал для режущих инструментов; токарный станок; многошпиндельные устройства; плоские поверхности; стационарный электрические станки; углеродистые стали; производство деталей машин и инструментов; серия режущих лезвий по окружности (фрезы); однолезвийный инструмент; быстрорежущие стали; двигаться параллельно или поперек направлению вращения; карбид вольфрама; нарезать резьбу; абразивный (шлифовальный) круг; световая, электрическая, химическая и звуковая энергия; штампы и пробойники; станки просверливающие отверстия; по этой причине; вдоль или под прямыми углами к станине; производственная линия.

III. Прочитайте слова, вспомните как переводятся прилагательные с отрицательным префиксом. Дайте несколько своих примеров:

indirectly; unconventional; unwanted.

IV. Сделайте грамматический разбор предложения, определите тип придаточного предложения и поставьте предложение в будущее время:

1. Hole-making machine tools are used to drill a hole where none previously existed. 2. It is, however, essential in tool rooms and job shops when a few identical pieces are being made. 3. The tool can be moved parallel to or across the direction of rotation to form parts that have a cylindrical or conical shape or to cut threads.

V. Прочитайте предложение, сделайте грамматический разбор, измените залог на противоположный:

These requirements are met, in varying degrees, by such cutting-tool materials as carbon steels, high-speed steels, tungsten carbide, and diamonds and by such recently developed materials as ceramic, carbide ceramic, and aluminum oxide.

VI. Найдите в предложениях место для наречий образа действия, стоящих в скобках. Предложения переведите:

1. The shaper is used to produce flat surfaces. (primarily) 2. Machine tools form the basis of modern industry and are used in the manufacture of machine and tool parts. (either directly or indirectly) 3. It uses a single-point tool and is slow. (relatively) 4. For this reason, the shaper is found on a production line. (seldom) 5. In many cutting operations fluids are used to cool and lubricate. (successfully)

VII. Ответьте письменно на следующие вопросы:

1. What is a machine tool?

2. What are they usually used for?

3. How can machine tools be classified?

4. What are conventional machine tools?

5. What are unconventional machine tools?

6. How does a lathe work?

7. Why aren’t shapers used on production line?

8. Where are shapers usually used and why?

9. What tool is used in a milling operation?

10. Are there different types of drilling machines?

11. Boring is a process that increases holes previously drilled, isn’t it?

12. Is grinding performed by rotating a workpiece or an abrasive wheel?

13. Don’t cutting processes include high local stresses, frictions, and heat generation?

14. What is used to reduce friction and increase tool life?

VIII. Переведите текст А письменно.

Text B

Unconventional Machine Tools

Unconventional machine tools include plasma-arc, laser-beam, electrodischarge, electrochemical, ultrasonic, and electron-beam machines. These machine tools were developed primarily to shape the ultrahard alloys used in heavy industry and in aerospace applications and to shape the materials used in such electronic devices as microprocessors.

Plasma Arc

Plasma-arc machining (PAM) employs a high-velocity jet of high-temperature gas to melt material in its path. The materials cut by PAM are generally those that are difficult to cut by any other means, such as stainless steels and aluminum alloys.

Laser

Laser-beam machining (LBM) is accomplished by accurate manipulating a beam of coherent light to vaporize unwanted material. LBM is particularly used to making accurately placed holes in refractory metals and ceramics and in very thin materials and can be used for welding.

Electrodischarge

Electrodischarge machining (EDM) employs electrical energy to remove metal from the workpiece. A pulsating high-frequency electric current is applied between the tool point and the workpiece, causing sparks that vaporize small areas of the workpiece. EDM can produce shapes which cannot be produced by any conventional machining process.

Electrochemical

Electrochemical machining (ECM) also uses electrical energy to remove material. An electrolytic cell is created in an electrolyte material where the tool is the cathode and the workpiece is the anode. A high-amperage, low-voltage current is used to melt the metal and to remove it from the workpiece.

Ultrasonic

Ultrasonic machining (USM) employs high-frequency, low-amplitude vibrations to create holes. A vibrated tool is placed against the workpiece while a mixture of fine abrasive and water flows between them. The friction of the abrasive particles cuts the workpiece. Materials such as hardened steel, carbides, rubies, quartz, diamonds can easily be machined by USM.

Electron Beam

In electron-beam machining (EBM), electrons are accelerated to a velocity nearly three-fourths that of light. The process is performed in a vacuum chamber to reduce the scattering of electrons. The electrons are directed against an accurately limited area of the workpiece; on impact, the kinetic energy of the electrons is converted into thermal energy that melts and vaporizes the material forming holes or cuts. EBM equipment is commonly used by the electronics industry to make circuits in microprocessors.

Задания к тексту B:

I. Найдите в тексте английские эквиваленты следующим русским выражениям:

электрохимическая обработка; ультратвердые сплавы; пульсирующий высокочастотный электрический ток; электроннолучевая обработка; необычные станки; лазерно-лучевая обработка; высокочастотные колебания с небольшой амплитудой; точное манипулирование лучом когерентного света; плазменная обработка; обработка ультразвуком; обработка посредством электрического разряда; приблизительно три четверти от скорости света; электролитическая ячейка; высокоскоростная струя горячего газа; высокий ток с низким напряжением.

II. Сформулируйте в нескольких словах содержание каждого абзаца.

III. Напишите резюме к тексту.

IV. Ответьте на вопросы:

1. What machines do unconventional machine tools include?

2. What were these machine tools primarily developed for?

3. What does plasma-arc equipment employ to melt material?

4. What materials can be cut with plasma-arc equipment?

5. What is laser-beam machining used for?

6. What energy does electrodischarge machining employ to remove metal from the workpiece without touching it?

7. In what material is an electrolytic cell created?

8. What current is used in electrochemical machining?

9. What does ultrasonic machining (USM) employ to create holes and other cavities?

10. What cuts the workpieces in ultrasonic machining?

11. What materials can be machined with USM?

12. What velocities are electrons accelerated to in electron-beam machining?

13. Where is the process performed and why?

14. Where is the EBM equipment commonly used?

V. Перескажите текст, используя в качестве плана вопросы предыдущего упражнения.