simply removing, adding, or changing the constituent units or modules of the system or the machine . The concept of modular design of machine tools is already well known . However, recent development of new machine hardware is opening new possibilities to modular design of machine tools .

Figure 1 shows a schematic illustration of typical 3-axis modular machining centers . The attention here is basically focused on how to increase reconfigurability of this type of machine tool.

Fig. 1 Modular machining centers Word study

Practice 1. Скажите, соответствуют ли данные предложения содержанию текста. Если нет, дайте правильный вариант ответа.

1. In designing modular machine tools a library of machine modules should be used.

2. Each module can not provide a fundamental motion .

3. In the case of machining systems, the reconfigurable machine tools should perform such processes as turning, milling, drilling and tapping or a combination of these processes .

4. The main purpose is to design an optimum rms in terms of cost, productivity, part quality and reconfiguration time .

5. The machinining systems can not easily be reconfigured by simply the basic units or modules of the systems of the machine .

The reconfigurable machine tools ...

The modular design of machine tools is a key ...

The machining system can easily be reconfigured ...

21

выбрав соответствующий вариант

should perform such processes as turning, milling, etc. .

a fundamental motion .

by simply removing, adding, or changing the constituent units .

enabling technology to reconfigurability.

Practice 3. Образуйте свои предложения , используя словосочетания Practice 2.

Practice 4. Ответьте на вопросы к тексту 6 .

1. What is used in designing modular machine tools ?

2. Can each module provide a fundamental motion ?

3. What kind of processes should machine tools perform ?

4. How can the machining systems be reconfigured ?

5. Is recent development of a new machine hardware opening new possibilities for modular design of machine tools ?

Practice 5. Перескажите текст, используя ответы на вопросы к тексту 6 в качестве плана.

Unit 7 Variation of products .

Text 7.

1. Прочтите текст, назовите основную цель создания реконфигурируемых станков (PC).

2. Перечислите возможные конструкционные изменения изделий .

3. Опишите реконфигурацию станка, связанную с размером заготовки .

4. Опишите реконфигурацию станка, связанную с геометрией детали .

5. Опишите реконфигурацию станка, обусловленную изменением процесса обработки.

Active vocabulary.

variation - изменение ; to соре (with) - справляться с чем либо ; part - деталь ; workpiece - заготовка ; complexity - сложность ; machine unit (module) - станочный узел (модуль); functionality - функциональность ; degree of freedom - степень свободы; motion unit - узел движения ; axis - ось ; to replace - заменять ; production rate (productivity - Производительность ; single- (multi) spindle unit - одно- (много-) шпиндельный узел ; rotary table - ; поворотный стол cutting tool - режущий инструмент ; turning - токарная оброботка ; milling - фрезерование ; drilling - сверление ; tool post - резцедержатель.

The primary aim of an RMT is to cope with various changes in the products or parts to be manufactured . The following possible changes must be taken into consideration ;

1. Workpiece size

2. Part geometry and complexity

3. Production rate

4. Required machining processes

Reсonfigurability for workpiece size . In order to cope with simple changes in the size of the workpiece, it will be enough to prepare machine units (modules), such as a column, table, spindle unit, etc. with different sizes . Reсonfigurability is achieved by changing modules . Reсonfigurability for part geometry . In order to increase the machine functionality for geometric complexity of the parts, the number of axes-of-motion is increased by adding new motion units or by replacing one of the units with one having several degrees of freedom . Figure 1 shows a schematic illustration of a possible reconfiguration of a 5-axis machining center . Some of the commercially available 5-axis machinines are reconfigured by replacing a rotary work-table with a three-axis table, and the others by replacing the spindle head with a versatile spindle-head unit.

Fig. 1 Assembly of modules for a rotary axis .

Reconfigurability for production rate. In order to increase production rate, the capacity of the machine spindle unit can be changed from single- spindle unit to dual - or even multi-spindle unit. The multispindle unit is a very powerful tool to increase the productivity. Modularized spindle units with different speed ranges and horsepower are good examples of utilizing RMTs. An example of an RMT is depicted in Fig.2, which shows a part mounted on a rotary table machined simultaneously with four spindles. The number of spindles may vary to acommodate the desired production rate. Each spindle is a module with a Z-axis. Two additional manual axes allow adjustment of the location of the spindle and its cutting angle .

Fig.2 Tор view of а vertical turning-milling center with multiple spindles