الاشتغال التلقائـي .. الحاسبات تعمل

Automation .. Computers work

Automatic operation

The use of automatic machine tools has been widespread for many years to produce small industrial parts in large numbers, which relieved the operators of regular machine tools from many repetitive routine tasks and directed them to more complex tasks. For example, in milling operations, a fixed rotary cutter is used to manufacture the parts clamped to the machine table by moving these pieces in all perpendicular directions, up or down, forward or backward, to the right or to the left. The operator of non-automatic machines adjusts these movements manually to obtain the desired shape.

(Automatic machine tools controlled by the computer: milling machine (up) and lathe machine (down).

As for automatic machines, a digital electronic computer issues signals to electric motors that move the table vertically, longitudinally or transversely. These signals are stored in advance on magnetic or paper tapes, which are rewound again and again to repeat the manufacture of the same piece. The movement of the table is controlled in different ways. Electro-optical devices may be used that emit an electric pulse every time the table moves about six parts of a thousandth of a millimeter in any of the three directions. The computer counts these pulses and stops the motor when the table reaches the desired position. Or an incremental method may be used that depends on stepping motors, each of which moves the table a small, specific distance in one of the three directions whenever it receives a signal from the computer. For example, if a longitudinal line is wanted to be cut in a piece, pulses of a specific rate are issued to the longitudinal motor, so the piece passes under the cutter at a constant speed, which increases with the increase in the rate Pulses. If the signals are sent at a constant rate to the longitudinal and transverse motors, the slit will be straight but angular. If the speed of the motors is adjusted in the correct proportion, the manufactured piece can be moved as required by the desired shape.

(A computer-controlled punching machine).
(Basic operations for forming with machine tools).

While the recorded pulses control the motors easily, the difficulty lies in generating the pulses in the required sequence and in the correct proportion between those that control different motors. This task is undertaken by a complex program in the computer that translates what is specified in a language specific to controlling machine tools into the pulses appropriate to the desired shape and the manufactured material. For example, if it is desired to cut a straight line between two points at a certain speed, the instructions in this control language specify the starting point of the line, its ending point and the required speed. The program in the computer, based on these instructions, generates the necessary pulses at the correct rate.

It is obvious that a program like this makes it much easier to adjust the movement of the machine tool table, but preparing these programs requires a great deal of effort, and they must be tested many times in making experimental pieces, until they are completely correct and used in the mass production of the relevant pieces. The computer's task in fully automatic systems is not limited to adjusting the movement of the table, but the computer also takes care of clamping the manufactured piece to the table and releasing it after completing the required operations and rewinding the magnetic tape in preparation for receiving a new piece.