Non-consumable Electrode Arc Welding

 

As a non-consumable electrodes tungsten or carbon electrodes can be used. In gas-tungsten arc welding a tungsten electrode is used in place of the metal electrode used in shielded metal-arc welding. A chemically inert gas, such as argon, helium ['hi:liэm], or carbon dioxide is used to shield the metal from oxidation. The heat from the arc formed between the electrode and the metal melts the edges of the metal. Metal for the weld may be added by placing a bare wire in the arc or the point of the weld. This process can be used with nearly all metals and pro­duces a high-quality weld. However, the rate of welding is considerably slower than in other processes.

Gas-Metal Arc

 

In gas-metal welding, a bare electrode is shielded from the air by surrounding it with argon or carbon dioxide gas and sometimes by coating the electrode with flux. The electrode is fed into the electric arc, and melts off in droplets that enter the liquid metal of the weld seam. Most metals can be joined by this process.

Submerged Arc

 

Submerged-arc welding is similar to gas-metal arc welding, but in this process no gas is used to shield the weld. Instead of that, the arc and tip of the wire are sub­merged beneath a layer of granular, fusible material that covers the weld seam. This process is also called electroslag welding. It is very efficient but can be used only with steels.

 

Resistance Welding

 

In resistance welding, heat is obtained from the re­sistance of metal to the flow of an electric current. Elec­trodes are clamped on each side of the parts to be welded, the parts are subjected to great pressure, and a heavy current is applied for a short period of time. The point where the two metals touch creates resistance to the flow of current. This resistance causes heat, which melts the metals and creates the weld. Resistance welding is widely employed in many fields of sheet metal or wire manufac­turing and is often used for welds made by automatic or semi-automatic ['semi,o:tэ'mætik] machines especially in automobile industry.

 

Vocabulary

 

gas-tungsten сварка оплавлением вольфрамовым электродом в среде инертного газа

inert [i'nэ:t] инертный

edge [ed₃] край

bare [bεэ] голый

rate [reit] зд. скорость

gas-metal arc аргоно-дуговая сварка

considerably [kэn'sidэrэbli] значительно, гораздо

surrounding [sэ'raundiŋ] окружающий

carbon dioxide ['ka:bэn dai'oksaid] углекислый газ

droplet ['droplit] капелька

liquid ['likwid] жидкость, жидкий

beneath [bi'ni:θ] под, ниже, внизу

layer ['leiэ] слой

weld seam [si:m] сварной шов

resistance [ri’zistэns] сопротивление

clamp [klæmp] зажим, зажимать

sheet [∫i:t] лист

fusible ['fju:zэbl] плавкий

granular ['grænjulэ] плавкий

semi-automatic ['semi,o:tэ'mætik] полуавтомати­ческая

to create [kri:'eit] создавать

to submerge [sэb'mэ:d₃] погружать

Can you answer the following questions?

 

1. What is the difference between the arc-welding and non-consumable electrode arc welding?

2. What are the disadvantages of the non-consumable electrode arc welding?

3. How is electrode protected from the air in gas-metal arc welding?

4. What is submerged arc welding?

5. What is the principle of resistance welding?

6. Where is semi-automatic welding employed?

Text 22. AUTOMATION

 

Automation is the system of manufacture perform­ing certain tasks, previously done by people, by machines only. The sequences of operations are controlled auto­matically. The most familiar example of a highly auto­mated system is an assembly plant for automobiles or other complex products.

The term automation is also used to describe non-manufacturing systems in which automatic devices can op­erate independently of human control. Such devices as automatic pilots, automatic telephone equipment and automated control systems are used to perform various operations much faster and better than could be done by people.

Automated manufacturing had several steps in its development. Mechanization was the first step necessary in the development of automation. The simplification of work made it possible to design and build machines that resembled the motions of the worker. These specialized machines were motorized and they had better production efficiency.

Industrial robots, originally designed only to perform simple tasks in environments dangerous to human work­ers, are now widely used to transfer, manipulate, and position both light and heavy workpieces performing all the functions of a transfer machine.

In the 1920s the automobile industry for the first time used an integrated system of production. This method of production was adopted by most car manufacturers and became known as Detroit automation.

The feedback principle is used in all automatic-con­trol mechanisms when machines have ability to correct themselves. The feedback principle has been used for centuries. An outstanding early example is the flyball governor, invented in 1788 by James Watt to control the speed of the steam engine. The common household ther­mostat is another example of a feedback device.

Using feedback devices, machines can start, stop, speed up, slow down, count, inspect, test, compare, and measure. These operations are commonly applied to a wide variety of production operations.

Computers have greatly facilitated the use of feedback in manufacturing processes. Computers gave rise to the development of numerically controlled machines. The motions of these machines are controlled by punched paper or magnetic tapes. In numerically controlled ma­chining centres machine tools can perform several dif­ferent machining operations.

More recently, the introduction of microprocessors and computers have made possible the development of computer-aided design and computer-aided manufacture (CAD and CAM) technologies. When using these systems a designer draws a part and indicates its dimensions with the help of a mouse, light pen, or other input device. Af­ter the drawing has been completed the computer automatically gives the instructions that direct a machining centre to machine the part.

Another development using automation are the flex­ible manufacturing systems (FMS). A computer in FMS can be used to monitor and control the operation of the whole factory.

Automation has also had an influence on the areas of the economy other than manufacturing. Small comput­ers are used in systems called word processors, which are rapidly becoming a standard part of the modern office. They are used to edit texts, to type letters and so on.

Automation in Industry

 

Many industries are highly automated or use automa­tion technology in some part of their operation. In com­munications and especially in the telephone industry di­alling and transmission are all done automatically. Rail­ways are also controlled by automatic signalling devices, which have sensors that detect carriages passing a par­ticular point. In this way the movement and location of trains can be monitored.

Not all industries require the same degree of automa­tion. Sales, agriculture, and some service industries are difficult to automate, though agriculture industry may become more mechanized, especially in the processing and packaging of foods.

The automation technology in manufacturing and as­sembly is widely used in car and other consumer product industries.

Nevertheless, each industry has its own concept of automation that answers its particular production needs.

 

Vocabulary

 

automation [,o:tэ'mei∫эn] автоматизация

previously ['pri:vjэsli] ранее

sequence ['si:kwэns] последовательность

assembly plant сборочный завод

non-manufacturing непроизводственный

device [di'vais] устройство, прибор

resemble [ri'zembl] походить

efficiency [i'fi∫эnsi] эффективность

flyball governor центробежный регулятор

steam engine паровоз

household thermostat [‘θэ:mэ,stæt] бытовой термостат

facilitate [fэ'siliteit] способствовать

punched [pAnt∫t] перфорированный

aid [eid] помощь

dimension [di'men∫эn] измерение, размеры

 

Can you answer the following questions?

 

1. How is the term automation defined in the text?

2. What is the most «familiar example» of automation given in the text?

3. What was the first step in the development of automaton?

4. What were the first robots originally designed for?

5. What was the first industry to adopt the new integrated system of production?

6. What is feedback principle?

7. What do the abbreviations CAM and CAD stand for?

8. What is FMS?

9. What industries use automation technologies?

 

Text 23. TYPES OF AUTOMATION