CNC Machines and their control

Computer-controlled machines are the building blocks of FMS. The key feature of a 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, die operator needs only call up the program name or number, while a series of different workplaces can be machined without pausing to set the mm nine 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 he 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. For example, tools may be supplied on pallets, along conveyors with the workplaces, and be loaded manually. Then, the workplace is usually set up manually. In other causes, 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 machining centers. 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 heartsick can be controlled at various speeds, while the spindle speed also can be varied infinitely. Then each tool can be used as required, all these auctions being controlled automatically according to a present program. As a general rule, in FMS there are two common types of machining centers, those with vertical and those with horizontal spindles. The horizontal types are mostly used owing to their greater flexibility.

The table carrying the workplace can move horizontally in two planes, x and y, and it can also index around. Then, the spindle can be moved vertically. Thus, the workplace can 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 lop face. On a vertical spindle, the table can be moved in the x and у planes, while the spindle can move vertically.

As with lathes, so with machining centers, the spindle and Label 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 around 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 (АТС). Between the loading station and spindle there is a gripped 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. It is worthy of note that the most important features of CNC machines are the servomotors, which can be controlled so that they 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. It 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.

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New words and word combinations:

1) the control (controller) – устройство управления; 2) power supply – подвод энергии, энергопитание; 3) air supply – подвод воздуха; 4) hydraulic supply – подвод жидкости; 5) feedback device – датчики обратной связи; joint – соединение, шарнир; 6) actuator – исполнительный орган (механизм);       7) gripping device – захватное устройство; 8) memory (programme storage) – устройство памяти; 9) stepping switches - шаговые переключатели; 10) valve – клапан, распределитель; 11) heat exchanger – теплообмениватель; 12) power (supply) unit – энергоблок (питание); 13) filter – regulator - фильтр с регулятором; 14) сartesian – картезианский, декартовский.