Методичка по английскому языку для ИТС (пр. С.С.Иванов)
.pdf―hazardous‖, for processes and the life cycle of chemical substances. Green chemistry is a way of dealing with risk reduction and pollution prevention by addressing the intrinsic hazards of substances rather than dealing with the conditions of their use that might increased their risk (e.g. exposure in the working environment, or uses of the products with exposure potential)
Risk, in its most fundamental terms, is the product of hazard and exposure:
= ( )
To calculate the risk associated with a certain substance we have to quantify its hazard (how toxic or dangerous to humans and the environment it is) and multiply it with a quantifiable exposure (dose, time, etc.). In the past, all common approaches to risk reduction focused on reducing exposure to hazardous substances and regulations often required increases in control technologies and treatment technology (i.e. personal protective equipment in order to reduce risk by restricting exposure). Green Chemistry goes to the heart of risk prevention or adequate reduction in advance before the substance is made or used. Green Chemistry demands to design products and use raw materials with lower hazardous properties as practical as possible. Green chemistry takes into account the difficulties and practical considerations in industrial processes, but puts first prevention than remedial action afterwards.
The definition of Green Chemistry and Its Principles illustrates another important point about the use of the term ―hazard‖. This term is not restricted to physical hazards such as explosiveness, flammability, and corrosibility, but includes acute and chronic toxicity, carcinogenicity, environmental pollution to water, air and soil (aquatic organisms, mammals, etc.) and ecological toxicity.
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Module 3. Machine building
The Milling Machine
Eli Whitney, of New Haven, Conn., invented one of the first milling machines in 1812. While it looks incredibly simple, it replaced the slow, antiquated process of hand-filing parts — thereby paving the way for interchangeable part production. Whitney used this milling machine and the concept of interchangeable parts to produce large quantities of muskets for the U.S. Army.
In 1861, Joseph R. Brown— Brown & Sharpe Co., Providence, R.I. — built a universal milling machine for the purpose of machining grooves in twist drills — a job that was still being done by hand-filing. The machine also proved capable of other types of spiral-milling, gear-cutting, and other metal-cutting.
Brown‘s machine caused a mild sensation on the American manufacturing scene because it incorporated many technological advances. It featured increased power and rigidity, an improved feed system, a better cross feed, and the use of stop nuts. The most significant advance, however, was the introduction of the column and knee principle. This new design concept solved the problem of vertical adjustment of the cutter relative to the workpiece.
By 1867, Brown & Sharpe milling machines featured micrometre dials, graduated in thousandths. Both the cross feed and the vertical movement screw connections had graduated circles on a plate and a pointer behind the crank to indicate a setting on these graduations.
The Cincinnati Milling Machine Co. brought out its No. 3plain milling machine in 1898. It is a column and knee machine, like Brown‘s early model, but it had a larger capacity for heavier industrial applications. The No. 3 had an automatic feed system with a powered table movement of 33 inches, a vertical range of 20 inches, and a cross motion of nine inches. It also had 10 spindle speeds.
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Figure 1. |
Figure 2. Whitney’s |
Figure 3. Brown and |
Cincinnati’s |
milling machine |
Sharpe’s first |
milling machine |
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universal milling |
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|
machine |
The Lathe
The lathe is one of the most useful and versatile machines in the workshop, and is capable of carrying out a wide variety of machining operations. The main components of the lathe are the headstock and tailstock at opposite ends of a bed, and a tool-post between them which holds the cutting tool. The toolpost stands on a cross-slide which enables it to move sidewards across the saddle or carriage as well as along it, depending onthe kind of job it is doing. The ordinary centre lathe can accommodate only one tool at a time on the tool-post, but a turret lathe is capable of holding five or more tools on the revolving turret. The lathe bed must be very solid to prevent the machine from bending or twisting under stress.
The headstock incorporates the driving and gear mechanism, and a spindle which holds the workpiece and causes it to rotate at a speed which dependslargely onthe diameter of the workpiece. A bar of large diameter should naturally rotate more slowly than a very thin bar; the cutting speed of the tool is what matters. Tapered centres in the hollow nose of the spindle and of the tailstock hold the work firmly between them. A feed-shaft from the headstock drives the tool-post along the saddle, either forwards or backwards, at a fixed and uniform speed. This enables the operator to make accurate cuts and to give the work a good finish. Gears between the spindle and the feed-shaft control the speed of rotation of the shaft, and therefore the forward or backward movement of the tool-post. The gear which the operator will select depends onthe type of metal which he is cutting and the amount of metal he has to cut off. For a deep
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or roughing cut the forward movement of the tool should be less than for a finishing cut.
Centres are not suitable for every job on the lathe. The operator can replace them by various types of chucks, which hold the work between jaws, or by a front-plate, depending onthe shape of the work and the particular cutting operation. He will use a chuck, for example, to hold a short piece of work, or work for drilling, boring or screw-cutting. A transverse movement of the toolpost across the saddle enables the tool to cut across the face of the workpiece and give it a flat surface. For screw-cutting, the operator engages the leadscrew, a long screwed shaft which runs along in front of the bed and which rotates with the spindle. The lead-screw drives the tool-post forwards along the carriage at the correct speed, and this ensures that the threads on the screw are of exactly the right pitch. The operator can select different gear speeds, and this will alter the ratio of spindle and lead-screw speeds and therefore alter the pitch of the threads. A reversing lever on the headstock enables him to reverse the movement of the carriage and so bring the tool back to its original position.
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A centre lathe
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LESSON 1
Words to be remembered
lathe chuck - токарныйпатрон, wobble - качаться; биение, jaw -
кулачок /патрона/, screw - винт, wear - износ, shank-хвостовик, faceplate -
разметочнаяплита, планшайба.
Read the following words:
wobble ['wɔbl], turn [tɜːn], screw [skruː], jaw [ʤɔː], independent ˌɪndɪ'pendənt], universal [ˌjuːnɪ'vɜːs(ə)l], wear [wɛə], insert ['ɪnsɜːt] , pressure
['preʃə], mechanical [mɪ'kænɪk(ə)l], kind [kaɪnd], equip [ɪ'kwɪp].
Translate the following derivatives paying attention to the prefix "re":
remake (v), reuse (v, n), reread (v), readjust (v), reconstruct (v).
Explain the difference between the following grammar forms:
is turning - is turned; are using - are used; is moving - is moved.
Explain the derivations of the following words:
to use - usage - useful - useless; to prepare - preparation - preparative; metal - metallic.
Lathe Chucks
The lathe chuck is used for chucking the work that is for clamping it so that it will rotate without wobbling while turning. It should be screwed on the headstock spindle while the lathe is stopped. There are two kinds of lathe chucks: the four-jaw independent chuck and the three-jaw universal chuck.
If the work is perfectly round it may be chucked in the so-called threejaw universal chuck all the jaws of which are moved to the centre by turning the
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screw. The four-jaw independent chuck has four jaws and each jaw has to be moved separately; it is mostly used to hold a work that is not perfectly round.
The jaws of the chuck are made of hardened and tempered steel to prevent their wear. The tapered shank-of the chuck is inserted into the taper hole of the headstock spindle.
Magnetic chucks are adapted to work which is difficult to hold in chuck jaws, either on account of its shape or because the pressure of the jaws may distort the work. The magnetic chucks have no jaws, as the work is held by magnetic force instead of by mechanical means, Some workpieces are so shaped that they cannot be held in a chuck, and work of this kind is often clamped to a faceplate. Most lathes are equipped with two faceplates: one small plate is used for driving workpieces turned between centres, and a large one is used to hold heavy or irregularly shaped pieces.
Exercises
I. Giving answers to the following questions,describe the lathe chucks.
What is a chuck?
What types of chucks do you know?
What purposes are chucks used for?
What kind of work are magnetic chucks adapted to?
How is the work held in a magnetic chuck?
How many faceplates are most lathes equipped with?
II. Compose questions to words written in bold.
1. He was looking for the new reference-book on elements of machines everywhere. 2. For a number of years scientists will be working at improving the machine-tool efficiency. 3. In machining operations the tool is moving и to the work.
III. Translate into Russian, paying attention to the Participles.
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1. When fastened in a lathe chuck, the work turns without wobbling. 2. All standard chucks are constructed entirely of steel having a solid steel body, and all the moving parts are made of hardened alloy steel to withstand wear. 3. Standard chucks can be furnished with either two or three simple jaws. 4. They are mechanically operated by an automatic mechanism which gives the operator total freedom of both hands for handling the work.
IV. Ask your friends if
1. the lathe chuck will rotate without wobbling while turning. 2. the jaws of the chuck are made of hardened and tempered steel to prevent wear. 3. most lathes are equipped with two faceplates. 4. the jaws are moved to the centre by turning the screw.
Dialogue
- As far as I know, the lathe chuck should be screwed on the headstock spindle.
-That‘s right. It should be screwed on the headstock spindle while the lathe is stopped.
-And how many lathe chucks are there?
-Well, there are two kinds of lathe chucks: the four-jaw independent chuck and the three-jaw universal chuck.
-As far as I remember, the jaws of the chuck are made of hardened and tempered steel.
-Exactly so. The jaws of the chuck are made of hardened and tempered steel to prevent their wear.
-Will you tell me a few words about magnetic chucks?
-Certainly. The magnetic chucks have no jaws, as the work is held by magnetic force instead of mechanical means.
LESSON 2
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Words to be remembered:
the live centre -подвижныйцентр,the dead centre -непод- вижныйцентр,to prevent - предотвращать,wear - износ,to align- центрировать,to test - испытывать, to measure - измерять,to install - устанавливать,a tapered shank - коническийхвостовик,to heat - нагревать,friction - трение,running centre - вращающийцентр.
Read the following words:
piece [piːs], centre ['sentə], together [tə'geðə], dead[ded], rub [rʌb], wear [wɛə], during ['djuərɪŋ], perform [pə'fɔːm], each [iːʧ], angle ['æŋgl], clean [kliːn], both [bəuθ], turner ['tɜːnə],cut[kʌt], alignment [ə'laɪnmənt], measurement ['meʒəmənt], same [seɪm], should [ʃud], install [ɪn'stɔːl], excessive [ɪk'sesɪv ], [ek-], call [kɔːl].
Underline the suffixes and prefixes and translate Into Russian:
to adjust, adjustable, adjusting, adjustment; to continue, continual, continuance, continuation, discontinuation, discontinuance, to discontinue; to divide, divided, division, divisor, to subdivide, subdivisible, subdivision.
Translate the following sentences into Russian paying attention to the underlined words.
1. We have provided our plants with various safety devices. 2. Provided the plant fulfills its plan ahead of time all the workers will get premiums. 3. The plants provided with such, machinery have higher labour productivity.
Lathe Centres
When machining a piece of work on a lathe the former is usually mounted between the lathe centres.
The two lathe centres are used to support the work: one - the live centre is held in the headstock spindle and turns together with the spindle and the work,the other - the dead centre is held in the tailstock spindle and in most
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cases does not turn and rubs against the workpiece. The point of the dead centre should be hardened to prevent its wearing during the operations performed on the lathe.
Good work depends to a great degree upon the condition of the lathe centres. Bach point must have an angle of 60 degrees and the centres as well as the spindle holes must be very clean.
Both lathe centres should always be aligned, i.e. the points are to meet when the tailstock with its centre is moved up to the headstock centre. A turner tests the alignment of the centres by taking a cut and then measuring both ends of the cut by a micrometer. Both measurements being the same, the centres are aligned and the turning may go on. Having got different measurements the worker has to change the position of the dead centre by turning the screw again, then another cut must be made for another test. This should be repeated until both measurements are the same.
Usually the centre consists of a cone oh which the work is installed and of a tapered shank. Works ate being machined at high speeds, a dead centre and the work will.be heated up so as to cause excessive wear from friction. In such cases the so called running centres are used.
Comprehension.
1. What is the most widely used method of holding work in the lathe? 2. Where are the two lathe centres mounted on the lathe? 3. What kinds of centres are used on lathes? 4. What is the alignment? 5. How does the turner test the alignment?6. What does the centre consist of? 7. What will cause excessive wear?
Use the following words and phraso3 in sentences of your own:
to mount, live centre, dead centre, headstock, tailstock, to align, the point, to prevent, should be hardened, condition, high speed, wear, to cause, running centre, to use.
Find in the text English equivalents for:
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