Machine toolA machine tool is a machine, typically powered other than by human muscle (e.g., electrically, hydraulically, or via line shaft), used to make manufactured parts (components) in various ways that include cutting or certain other kinds of deformation. All machine tools involve some kind of fundamental constraining and guiding of movement provided by the parts of the machine, such that the relative movement between workpiece and cutting tool (which is called the toolpath) is controlled or constrained by the machine to at least some extent, rather than being entirely “offhand” or “freehand”. Machine tools archetypically perform conventional machining or grinding on metal (that is, metal cutting by shear deformation, producing swarf), but the definition can no longer be limited to those elements, if it ever could, because other processes than machining may apply, and other workpiece materials than metal are common. Machine tools were born when the toolpath first became guided by the machine itself so that direct human guidance of the toolpath (with hands or feet) was no longer the only guidance used in the cutting or forming process. (1.) ______________________________________________________________________. First is the spindle concept, which constraints workpiece or tool movement to rotation around a fixed axis. Then comes the machine slide, which has many forms, such as dovetail ways, box ways, or cylindrical column ways. (2.) ______________________________________________________________________. The third important concept is tracing, which involves following the contours of a model or template and transferring the resulting motion to the toolpath. Finally, there’s Cam operation, which is related in principle to tracing but can be a step or two removed from the traced element’s matching the reproduced element’s final shape. When considering the difference between freehand toolpaths and machine-constrained toolpaths, the concepts of accuracy and precision, efficiency, and productivity become important in understanding why the machine-constrained option adds value. With a machine tool, toolpaths that no human muscle could constrain can be constrained; and toolpaths that are technically possible with freehand methods, but would require tremendous time and skill to execute, can instead be executed quickly and easily. Machine tools can be operated manually, or under automatic control. Early machines used flywheels to stabilize their motion. (3.) _____________________________________________________________________. NC machines used a series of numbers punched on paper tape or punched cards to control their motion. In the 1960s, computers were added to give even more flexibility to the process. Such machines became known as computerized numerical control (CNC) machines. NC and CNC machines could precisely repeat sequences over and over, and could produce much more complex pieces than even the most skilled tool operators.
Exercise 7. Answer the following questions about the text.
1. What is a machine tool? 2. What do machine tools archetypically perform? 3. Why can the definition no longer be limited to those elements? 4. Do you think it is right to say that all machine tools are “machines that help people to make things”, although not all factory machines are machine tools? 5. What are the root concepts behind the mechanical toolpath guidance? 6. How do machine-constrained toolpaths differ from freehand toolpaths? What are their advantages? 7. Machine tools can be powered from a variety of sources, can they not? 8. What is a NC machine? What is a CNC machine?
Exercise 8. Complete the sentences with the information from the text.
1. A machine tool is a machine, typically powered other than by … (e.g., …, …, or via …), used to make … in various ways that include cutting or certain other kinds of deformation. 2. Machine tools archetypically perform conventional …. 3. Machine tools were born when …. 4. The first root concept that the mechanical toolpath guidance grew out of is … which constraints workpiece or tool movement to rotation around a fixed axis. 5. The second one is …, which has such forms as dovetail ways, box ways, or cylindrical column ways. 6. The third important concept is …, which involves following the contours of a model or template and transferring the resulting motion to the toolpath. 7. The last but not the least is …, which can be a step or two removed from the traced element’s matching the reproduced element’s final shape. 8. The difference between freehand toolpaths and machine-constrained toolpaths lies in the concepts of …, …, and … which add …. 9. … and … machines could precisely repeat sequences over and over, and could produce very complex pieces.
Exercise 9. Match the terms from the text to their Russian equivalents.
Exercise 10. Find in the text the English equivalents for the following Russian words and phrases.
Мускульная сила человека; деформация сдвига; фундаментальное ограничение; относительное движение; деформация сдвига; стало управляемым непосредственно машиной; процесс резки или формирования; ограничить движение инструмента или заготовки; калькирование; следовать контурам модели или шаблона; кулачковый механизм; соответствовать окончательной форме воспроизводимого элемента; требовать много времени и умения для выполнения; управляться вручную или автоматически; придать процессу большую гибкость; точно повторять последовательности; производить намного более сложные элементы; самые квалифицированные операторы.
Exercise 11. Find in the text the following English words and phrases and give their Russian equivalents.
Typically powered by; manufactured parts; other kinds of deformation; to at least some extent; archetypically; no longer; if it ever could; common; dovetail ways, box ways, or cylindrical column ways; is related in principle to; when considering the difference between; with a machine tool; freehand methods; to stabilize their motion; became known as; numerical control (NC) machines; computerized numerical control (CNC) machines; repeat sequences over and over; much more complex pieces.
Exercise 12. Read the text again and divide it into paragraphs (logically, you may have four or five of them).
Exercise 13. Read the following text quickly to get an idea of what it is about. Ignore the words you do not know. Choose the most suitable heading from the list A-H for each part (1-7). There is one heading which you do not need.
1. A laser is a device that emits light (electromagnetic radiation) through a process of optical amplification based on the stimulated emission of photons. The term “laser” originated as an acronym for Light Amplification by Stimulated Emission of Radiation. The emitted laser light is notable for its high degree of spatial and temporal coherence, unattainable using other technologies. In modern usage “light” broadly denotes electromagnetic radiation of any frequency, not only visible light, so we speak about infrared laser, ultraviolet laser, X-ray laser, and so on. 2. A laser consists of a gain medium inside a highly reflective optical cavity, as well as a means to supply energy to the gain medium. The gain medium is a material with properties that allow it to amplify light by stimulated emission. In its simplest form, a cavity consists of two mirrors arranged such that light bounces back and forth, each time passing through the gain medium. Typically one of the two mirrors, the output coupler, is partially transparent. The output laser beam is emitted through this mirror. 3. The invention of laser would have been impossible without the ideas and developments of Albert Einstein, Max Planck, Rudolf W. Ladenburg, Willis E. Lamb and R. C. Retherford, and Alfred Kastler. In 1953, Charles Hard Townes and graduate students James P. Gordon and Herbert J. Zeiger produced the first microwave amplifier, a device operating on similar principles to the laser, but amplifying microwave radiation rather than infrared or visible radiation. Townes's maser was incapable of continuous output. Meanwhile, in the Soviet Union, Nikolay Basov and Aleksandr Prokhorov were independently working on the quantum oscillator and solved the problem of continuous-output systems by using more than two energy levels. In 1955, Prokhorov and Basov suggested optical pumping of a multi-level system as a method for obtaining the population inversion, later a main method of laser pumping. In 1957, Charles Hard Townes and Arthur Leonard Schawlow, then at Bell Labs, began a serious study of the infrared laser. As ideas developed, they abandoned infrared radiation to instead concentrate upon visible light. The concept originally was called an “optical maser”. In 1964 Charles H. Townes, Nikolay Basov, and Aleksandr Prokhorov shared the Nobel Prize in Physics, “for fundamental work in the field of quantum electronics, which has led to the construction of oscillators and amplifiers based on the maser – laser principle”. 4. When lasers were invented in 1960, they were called “a solution looking for a problem”. Since then, they have become ubiquitous, finding utility in thousands of highly varied applications in every section of modern society, including consumer electronics, information technology, science, medicine, industry, law enforcement, entertainment, and the military. The first use of lasers in the daily lives of the general population was the supermarket barcode scanner, introduced in 1974. The laserdisc player, introduced in 1978, was the first successful consumer product to include a laser but the compact disc player was the first laser-equipped device to become common, beginning in 1982 followed shortly by laser printers. 5. Even the first laser was recognized as being potentially dangerous. Theodore Maiman characterized the first laser as having a power of one “Gillette” as it could burn through one Gillette razor blade. Today, it is accepted that even low-power lasers with only a few milliwatts of output power can be hazardous to human eyesight, when the beam from such a laser hits the eye directly or after reflection from a shiny surface. At wavelengths which the cornea and the lens can focus well, the coherence and low divergence of laser light means that it can be focused by the eye into an extremely small spot on the retina, resulting in localized burning and permanent damage in seconds or even less time. 6. Laser beams are famously employed as weapon systems in science fiction, but actual laser weapons are still in the experimental stage. The general idea of laser-beam weaponry is to hit a target with a train of brief pulses of light. The rapid evaporation and expansion of the surface causes shockwaves that damage the target. The power needed to project a high-powered laser beam of this kind is beyond the limit of current mobile power technology thus favoring chemically powered gas dynamic lasers. On March 18, 2009 Northrop Grumman claimed that its engineers in Redondo Beach had successfully built and tested an electrically powered solid state laser capable of producing a 100-kilowatt beam, powerful enough to destroy an airplane or a tank. According to Brian Strickland, manager for the United States Army’s Joint High Power Solid State Laser program, an electrically powered laser is capable of being mounted in an aircraft, ship, or other vehicle because it requires much less space for its supporting equipment than a chemical laser. However the source of such a large electrical power in a mobile application remains unclear. 7. Several novelists described devices similar to lasers, prior to the discovery of stimulated emission. A laser-like device was described in Alexey Tolstoy’s science fiction novel The Hyperboloid of Engineer Garin in 1927. Mikhail Bulgakov exaggerated the biological effect (laser bio stimulation) of intensive red light in his science fiction novel Fatal Eggs (1925), without any reasonable description of the source of this red light. (In that novel, the red light first appears occasionally from the illuminating system of an advanced microscope; then the protagonist Prof. Persikov arranges the special set-up for generation of the red light.)
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