Министерство высшего и среднего специального образования СССР
Московское ордена Ленина, ордена Октябрьской Революции
и ордена Трудового Красного Знамени
высшее техническое училище им. Н. Э. Баумана
Н. Н. Прозоровская
по обучению чтению технической
литературы на английском языке
по специальности «прессы»
Под редакцией Л.М. Степановой
Глава 1. METALFORMING – AGRAFTWITHROOTSDEEPINTHEPAST.
Предтекстовые задания. Повторите лексику, значение незнакомых слов найдите в словаре:
Accuracy, ancillary, appreciate, at least, convenient, direction, demand, enhance, flywheel, generate, hammer, labour, major, means, medium, prohibit, precesion, remain, single, stroke, substitute, versatile.
Определите по суффиксам, к каким частям речи относятся следующие слова, переведите:
Прочитайте текст А и выполните задания, данные после предъявления текста.
The first step in the automation of sheet metal working, a craft with roots deep in the pasr was undoubtedly the introduction of the flywheel as a means of providing the explosion of energy needed to perform at one stroke the work of thousands of hammer blows.
By the late 1800’s flywheel driven machines were in use for almost all the known ways of working sheet metal. Guillotines cut sheets into convenient blanks and strip, angle benders formed the strips, presses coined, blanked, stamped, formed, punched and drew their way into the sheet metal manufacturing industry.
At the turn of the century the industry was well established although largely labour intensive. Men and women operators fed countless numbers of blanks into the tools and removed the same countless numbers of components. Whilst labour was cheap and demand low the situation remained fairly stable and consequently development was slow. Means of automatically feeding presses were available and coiled strip was in use and although automatic machinery was used in certain specialized areas, such as can making, most general press work was still hand fed.
Between the wars development continued but mainly as consolidation and improvement of existing types of machines and methods of feeding. When costs and markets increased after the second world war, means of reducing labour and increasing production were in much greater demand. Existing presses were provided with feeding equipment of all types, roller feeding generated an increased demand for sheet metal in coil form and a new industry developed from the need of manufacture. Presses and feeds were specially designed as high speed production units, mainly for the manufacture of small components at first but soon progressing to larger and more complex parts.
APPEARANCE OF HYDRAULICS
The flywheel remained the basis of the industry but hydraulics were beginning to be substituted in some of the heavier machines where the cost and size of huge mechanical drives was prohibitive. The advantages of individual pump units were soon appreciated and hydraulically powered guillotines and press brakes appeared on the market and were quickly accepted by the industry.
Hydraulic presses had been available in various forms for many years but now they became in more general use for sheet metal work, both as light tonnage machines and as alternatives to heavy flywheel driven double and triple action drawing, presses.
On the small and medium tonnage presses, as the demand for higher speeds and automatic feeds increased, the mechanical clutch began to reveal its disadvantages. The air operated friction clutch, with its capability of higher engagement speed(1) and part stroke stopping, became the natural replacement. By the 1960’s the pneumatic clutch and combined spring operated brake(2) was standard equipment on automatically fed presses and in widespread use on many single operation presses. The development of this type of clutch, controlled by a solenoid operated air valve, encouraged the development of complex electrical control systems.
By this time the shape of presses was also changing as cast iron began to give way to welded steel frames, a more versatile material with a much greater potential for large press construction.
By the early ‘60’s(4) electronics had already made an impact on the machine tool industry but few manufacturers had attempted to apply the new techniques to the sheet metal working industry. Possibly the first major success was the turret punch, which utilized established principles to control the two axis movement of the sheet under the punches. The press brake had by this time been put into use by the application of the photo electric operators quard and was given a further boost by the use of NC electronic equipment to control the sequential movement of the backstop. This, followed by the additional control of the bottom of stroke position, made possible very significant reduction in production times.
Developments in ancillary equipment were also taking place, the air operated gripper feed introduced in fifties was now widely used. Die hydraulics greatly enhanced the capabilities of standard presses and later, new methods of feeding strip were introduced which did not depend on precision mechanical drives for accuracy. By means of electronic measurement and closed loop control systems, errors caused by mechanical inaccuracies and speed variations were avoided.
Notes: (1) higher engagement speed – высокая скорость срабатывания
(2) combined sprign operated brake – комбинированный тормоз, нормально включенный под действием пружины
(3) to give way to – уступать
(4) by the early ‘60’s – к началу 60-х годов
Посмотрите 1 абзац, найдите ключевые слова, подтверждающие смысл названия. Найдите группу подлежащего и сказуемого, переведите.
Прочитайте 2-й абзац, выпишите подлежащие и сказуемые из каждого предложения, переведите.
Прочитайте 3-й абзац, выделите в каждом предложении сказуемое. В каких предложениях имеются явные признаки сказуемого? Переведите, обращая особое внимание на термины.
Light tonnage machine, heavy flywheel driven double and triple action drawing presses, air operated friction clutch, part stroke stopping, combined spring operated brake, solenoid operated air valve, complex electrical control system, sheet metal working, sheet metal manufacturing industry, hydraulic overload protection system, high speed production units.
Прочитайте первое предложение 10 абзаца, найдите цепочку слов, переведите.
Расчлените второе предложение 10 абзаца на простые предложения.
Прочитайте текст, определите в каком из 3-х разделов выделена главная мысль статьи, если исходить из заглавия.
19. Переведите 10 абзац, найдите ответы на данные ниже вопросы.
I.). What ancillary equipment introduced in the fifties was widely used?
2). By means of what were the capabilities of standard presses enchanced?
20. Посмотрите текст B , проверьте себя, какие технические термины Вам знакомы. Выделите интернациональную лексику.
TEXT B. MODERN TECHNIQUES
1. Presses are now being built in the UK which incorporate almost all the previously mentioned features, commissioned by users who are determined to make all possible use of modern techniques of control including robotic manipulation and handling devices. A large flywheel driven press may incorporate an electronically controlled variable speed drive, air or hydraulically operated clutch, air powered cushions with hydraulic locking, hydraulic tool clamps, hydraulic die control, digital electronic means for ram and cushion adjustment and stroke position, hydraulic powered feed equipment and moving bolsters for rapid tool changing. Strain gauges which accurately measure, display and record the tonnage exerted by the machine and hydraulic overload protection system are now also in common use. The advent of microprocessors, electronic sensing devices and photo electrics provides facilities for automatic control which were economically and practically impossible only a few years ago. Complete tool changes can be programmed, including the ram adjustment, ancillary equipment settings, tool clamp-unclamping.
2. The flywheel, electric motor and fluid powered systems all operate by the application of mechanical force to the sheet metal. New methods of working sheet, such as the laser, plasma are and magnetic force are now commercially available.
The UK sheet metal industry must now be ready to take full advantage of such innovations which will provide the potential for a step forward of similar magnitude to the introduction of the flywheel powered sheet metal working machinery.
3. A good example of the most advanced and sophisticated pieces of equipment is plasma cutting press. It is used for producing of stampings, generally of large size and relatively thick materials. The presses are punching and nibbling machines- They can be described as high-precision, high-speed turret punch presses that work from computer-generated NC tapes. How fast are they? A recent production of 1,000 pieces involved a rectangular part made from 1/2- inch thick mild steel. The Plasmapress gives the capability of producing limited runs of highly irregular shapes. With its combined high-speed nibbling and plasma cutting function, it is a remarkably versatile machine.
21. Прочитайте текст B. Какую новую информацию вы получили в добавление к тексту A.
1) What new methods of working sheet metal are now commercially available?
2) What gives full advantage to the UK sheet metal industry?
3) What can you say about plasma cutting press?
24.просмотрите текст С, найдите ответы на следующие вопросы:
1) Who designed new electrohydraulic, electromagnetic and hydroimpact forming equipment?
2) In what field of industry can new installation be used?
3) What does the biggest benefit come from?
25)Найдите главную мысль каждого раздела
26)Прочитайте 4 раздел, найдите ключевые слова, характеризующие электрогидравлическую и гидроимпульсную штамповки. Дайте их сравнительную характеристику.
27) Составьте реферат статьи.
TEXT C. NEW ENGINEERING PROCESSES
Soviet engineers and designers have developed simple and reliable installations for electrohydraulic, electromagnetic and hydroimpact pulse stamping operations, efficient in test laboratory applications in the instrument, automotive, tractor, electrical engineering and other related industries. The installations can be used in repair shops, and for limited production runs in the aircraft industry.
Broaching composite shapes in flat and three-dimensional components. Bending, shaping and extrusion, flaring and other similar assembly operations- these and other machining applications are handled by the pulse-type machines developed at the Physicotechnical Institute, Byelorussian SSR Academy of Sciences.
The biggest benefits come from limited production runs – 300 to 500 units a year, on varied range- 50 to 70 types and sizes and more a year. Depending on the particular operation, through-put ranger from 10 to 80 pieces an hour.
2. HIGH ACCURACY.
Component share corresponds to the die shape. The minimal radii of conjugation of the elements of three-dimensional components do not exceed 0.2 – sometimes 0.1 mm. Broaching accuracy meets the requirements of classes 2-4 under the USSR Standards.
3. SIMPLE AND LOW-COST TOOLING.
For stamping and punching-out only the die is used. Its dimensional accuracy generally corresponds to the dimensional specification of the component. The punch function is performed by water in electrohydraulic installation, by the forces of the electromagnetic field in electromagnetic equipment, and by either water or some elastic medium in hydroimpact designs. This makes for simpler stamp production technique, and there is no need to match the punch to the die.
Steel die used in applications requiring pulses rated over 8kj. Where the run 500 pices or less the die will be made of non-heat-treated general-purpose structural steel: heat treatment is required only for punching dies.
Where the energy is less than 8kj and the run is 30 stamping or less the die may be epoxy resin, gypsum sometimes even of ice.
All these features cut manufacturing costs by 80 to 90 percent against that of conventionally made tooling.
4. THERE FORMING PROGRESSES HANDIED ON TWO MACHINES.
Electrohydraulic stamping is generally performed by a shock wave produced by sending an electric discharge through water, while electromagnetic stamping is done with a specialpurpose inductor. What makes the new machine superior to conventional designs is its versatility: to switch from one machining mode to another all you have to do is to pull the discharge chamber out and replace the discharge electrode with an inductor.
The condenser battery of a total of 2.400 F capacity accumulates up to 25 kJ. By varying the discharge voltage within the range of 1 to 10 kV the useful energy is controlled to suit the nature of the article sramped and the material.
Hydroimpact shaping is performed by a striker impacting elastic medium.(1) The striker is accelerated to 50-100 m/s by compressed air supplied from the factory pressurized air line. (2) The energy of shaping may be as high as 20 kJ, with the pressure in the workings chamber reaching 2.000 kg/ cm^2. although these ratings are somewhat lower that in the case of electric impulse equipment, the hydroimpact presses offer the advantage of simpler sonstruction, the absence of high-voltage elements and higher efficiency.
Notes: 1) striking impacting elastic medium –ударное уплотнение, 2) factory pressurized air line- магистральный воздухопровод.
1.Повторите лексику, значение незнакомых слов найдите в словаре.
adjust, as far as, by means of, improvement, introduction, flexibility, level, loading, manual, maintenance, operating speed, stroke, suit, to be contrary to.
2.Восстановите словарную форму выделенных слов. Переведитепредложение.
In this traditional regards, the principle arguments against winder applications for hydraulic presses were their slow stroking, oil leakage and other maintenance problems as well as the noise made by the hydraulic power packs.
3.Переведите следующие слова как глаголы и как существительные:
point, speed, range, design, demand, use, slide, cycle, desire.
Задание к тексту.
1.Прочитайте текст А и выполните задания, данные после предъявления текста. TEXT A
1. The performance of hydraulic presses has developed to a point where they now complete successfully against mechanical presses over a wide range of applications and major developments in recent years have raised operating speeds to levels which allow these machines to compete even against single-acting mechanical presses. As a result of continued design improvements, both in the press and in hydraulic presses have been realized and have been reflected in increased user demand for an everwidening range of applications.
CHANGE IN EMPHASIS
2. For the majority of cold-forming operations, the single-acting mechanical downstroke press has been traditionally regarded as the “workhouse” of the industry and for shallow draw work the custom has been to use the double-acting mechanical press. Hydraulic presses have been considered to be applicable only to long-stroking operations such as deep drawing, where the controllability of hydraulic power is of prime importance.
3. In traditional regard, the principle arguments against wider applications for hydraulic presses were their slow stroking speed, old leakage and other maintenance problems, as well as the noise made by the hydraulic power packs.
4. As a result of the design improvements, major developments are taking place which have been already led to a new type of fast-acting presses which are arousing considerable interest in what usually was a predominantly mechanical press field.
5. Operating speeds
Central to new developments to improve operating speeds of hydraulic presses has been the introduction of the fast-acting logic valve. A 300 ton hydraulic press with a 200mm working stroke and a 3mm pressure stroke can now cycle, for example, in 2.4 sec when applied to coining, planishing and sizing operations,(fig 1).
6. It should be stressed, however, that while the high stroking speeds of mechanical presses can be utilized in conjunction with automatic feed gear, as in the case of blanking, the majority of medium-to-large press work in this country involves manual loading and in many cases manual unloading as well. Although the mechanical press in capable of stroking in around 2 sec, floor-to-floor time for this type of work, however, are typically of the order of 15 to 30 sec.
7. While emphasis is often laid on the operating speed of the press with regard to the overall cycle time (3), we have to consider the time for transportation by the development of automated handing and the introduction of more efficient guarding. Arising from the ability to lock the side on every stroke and at any position on an hydraulic press it has proved possible to adopt photocell guarding while conforming to the majority of applied safety regulations. Arranged automatically to cycle the press, the introduction of photocell guarding has, in itself, made a major contribution towards reducing overall cycling time.
8. It must be born in mind, however, that continuity of production is often more significant than speed of production and attention will continue to be focused on reducing downtime.
9. WHY HYDRAULIC?
It is the desire to realize the operating benefits of hydraulic presses which has stimulated press builders to break the hydraulic speed barrier. These benefits include the operating flexibility of an hydraulic press, the reduced down-time for tool setting, and the minimized risk of accidental tool damage. The key, of course, is provided by the controllability of hydraulic power.
10. CONTROLED PRESSURE.
The pressure on an hydraulic press depends on the setting of an adjustable relief valve which is regulated automatically from the operator’s console. This pressure is continually controllable from maximum down to approximately 20 per cent of its maximum value and is available throughout the work-stroke.
11. Through the complete work-stroke, the pressure of the system, therefore, is built up only to that required to overcome the resistance of the work-piece, and will increase only as far as the relief-valve pressure setting. As a consequence, it is almost impossible to overload an hydraulic press due, for example, to double-blanking or inaccurate die setting. Also, the length of stroke of the slide can be adjusted by means of limit switches to suits any depth of draw, any desired stroke being set in a matter of seconds. This is contrary to the mechanical press where the stroke cannot be altered, the full stroke of the crank having to take place regardless of the actual depth of draw. In addition, the pressure in a mechanical press builds up to an increasing and uncontrolled rate after midstroke to maximum power only at the end of the stroke.
12. For example, it can be said that to obtain 1000 tons at say 5in from stroke bottom the mechanical press would have to be up-rated to 3000 tons power, where as in the case of the hydraulic press the maximum power of 1000 tons is available through out the whole of the stroke.
Notes: 1. power pack – узел привода
2. floor – to – floor time – время перемещения от места к месту
3. overall cycle time – время полного цикла
2. Переведите I абзац текста , догадайтесь по смыслу о значении слов :
complete, benefit , inherent . Проверьте правильность по словарю.
3. Переведите 2 , 3 абзацы .Что определяется словосочетанием « workhorse in the industry»?
4. Прочитайте подчёркнутое предложение 2 абз., какая синтаксическая конструкция используется для характеристики работы гидравлического пресса.