Материал: 2177
4 |
initiate |
……………… |
начать, запускать |
5 |
machine shop |
……………… |
механический цех, мастер- |
|
|
|
ская |
6 |
direct numeri- |
……………… |
прямое ЧПУ |
|
cal control |
|
|
С |
……………… |
вспомогательное оборудо- |
|
7 |
ancillaries |
||
|
|
|
вание |
8 |
lathe |
……………… |
токарный станок |
9 |
slant-bed |
……………… |
токарный станок с наклон- |
|
|
|
ной станиной |
10 |
turret |
……………… |
револьверная головка |
11 |
spindle |
……………… |
вал, ось, шпиндель |
12 |
headstock |
……………… |
шпиндельная бабка |
13 |
index |
……………… |
поворачивать на определен- |
и |
ный угол |
||
14 |
setting |
……………… |
запуск |
15 |
attachment |
……………… |
дополнительное приспособ- |
|
|
А |
|
|
mountб……………… |
ление, устройство, насадка |
|
17 |
монтировать, устанавливать |
||
18 |
gripper |
……………… |
захват, зажим |
19 |
chuck |
……………… |
зажимной патрон, держа- |
|
|
|
тель |
II. Find the words in the text andДtranslate the word combinations with these words.
III. Work in pairs. Study the prompts in italicsИpaying attention to the use of the Articles. Think of 2 or 3 statements using the words from Ex. I. and discuss them in your group.
To initiate a particular program, the operator needs only call up the program name.
The features that make CNC the heart of an FMS can also be adopted on other machines.
81
IV. Read the text and label the pictures (pic. 18 – 25).
С |
|
|
|
|
|
и |
|
|
|
|
|
Pic. 18 ___________________ |
|
|
|
б |
|
|
|
|
|
А |
|
|
|
|
Pic. 19 |
|
|
|
|
Д |
|
|
|
Pic. 20 ______________ |
И |
|
|
|
Pic. 21_________________ |
|
||
82
С |
|
и |
Pic. 23_________________ |
Pic. 22 |
|
б |
|
А |
|
Pic. 24 _________________ |
Д |
Pic. 25 |
|
CNC MACHINES AND THEIRИCONTROL
Computer-controlled machines are the building blocks of FMS. The key feature of a computer numerical control (CNC) machine is that several steps can be carried out in sequence without manual labour, and a number of different series of machining operations can be stored in the controller. Therefore, to initiate a particular sequence or program, the operator needs only call up the program name or number, while a series of different workpieces can be machined without pausing to set the machine up or install new tools. It should be noted that the signal to initiate a program can come equally from a process computer controlling a whole machine shop. However, the features that make CNC the heart of an FMS can also be
83
adopted on other machines – for example, the CNC is almost the same as a robot controller.
In some installations, a number of CNC machines have been under minicomputer control and generally they are called DNC (direct numerical control) systems. Usually a DNC differs from an FMS in the ancillaries.
СFor example, tools may be supplied on wallets, along conveyors with the workpieces, and be loaded manually. Then, the workpiece is usually set up manually. In other cases, the system is designed to produce a small number of variations in a family of components, such as axles.
There are basically two types of CNC machines – lathes and machiningиcenters. All have similar control units. In a typical CNC lathe, there is a slant-bed with one or two turrets carrying tools for turning, boring, drilling and perhaps even grinding.
The movement of the tools both towards the spindle and towards the headstock canбbe controlled at various speed, while the spindle speed also can be varied infinitely. Then each tool can be used as required, all these functions being controlled automatically according to a present program.
As a general rule, in a FMS there are two common types of machining centres, those Аwith vertical and those with horizontal spindles. The horizontal types are mostly used owing to their greater flexibility.
The table carrying the workpiece can move horizontally in two planes, x and y, and it can also index around. Then, the spindle can be moved vertically. Thus, the workpieceДcan be indexed around 90° so that four faces can be machined at one setting. However, some machines either have a right angle attachment or have a special head design for machining the top face. On a vertical spindle, the table can be moved in the x and y planes, while the spindle can move vertically.
As with lathes, so with machining centres,Иthe spindle and table speeds can be varied infinitely, but, of course, to enable the machine to mill, drill, bore and tap, many different tools are needed. Therefore, a tool magazine is mounted on the side of the machine. The magazine is circular or rectangular, and it is indexed round so that the tool needed for the next operation can be moved in advance close to the loading station this device being called an automatic tool changer (ATC). Between the loading station and spindle there is a gripper which can pick up the tool from the spindle chuck – in some cases while the spindle is still rotating – remove it and place it in the magazine. Then it picks up the new tool and inserts it in the machine.
84
It is worthy of note that the most important features of CNC machines are the servo-motors, which can be controlled so that theу can rotate at any speed.
Next, with electronic controllers, it became practical to put a series of steps in sequence and initiate those steps automatically.
СIt should be noted that large memory is needed so that many programs can be stored, and more complex programs be used. Most of the new CNC machines take advantage of the large memory to include standard programs for such operations as drilling and deep drilling carried out in stages.
V.иComplete the sentences.
1. A process computer gives the signal to …
2. Direct numerical control systems are often called … 3. A DNC differsбfrom an FMS in …
4. The two types of CNC machines are …
5. In a FMS there are two common types of machining centers … 6. The magazine is …
7. A gripper is used toА…
8. Most CNC machines need large memory as …
VI. Summarize the text. Read the tips in Home task 5.
VII*. Would you like to work withДsuch a CNC machine (pic. 26)?
Why? What could you do with its help? И
Pic. 26
85