(1) The prepared machining program sends the digital information to the numerical control device through the keyboard or the input device on the operation panel.
(2) The numerical control device performs a series of processing on the received signal, and then distributes the processing result in the form of a pulse signal: one is to issue a feed, etc. to the feed servo system, and the other is to issue to the programmable controller. S, M, T and other command signals.
(3) After the programmable controller receives command signals such as S, M, T, etc., it controls the main body of the machine tool to execute these instructions immediately, and feeds back the real-time conditions of the main body of the machine tool to the numerical control device.
(4) After the servo system receives the feed execution command, it immediately drives the axes of the main body of the machine (feed mechanism) to accurately perform the displacement in accordance with the instructions and automatically complete the processing of the workpiece.
(5) In the displacement process of each coordinate axis, the feedback device quickly feedbacks the measured value of the displacement to the numerical control device to compare it with the command value, and then sends the compensation execution command to the servo system at a very fast speed until the measured value is The command value agrees.
(6) In the process of displacement of each coordinate axis, if an "overtravel" phenomenon occurs, the limit device can send signals of certain axis overtravel to the programmable controller or directly to the numerical control device. On the other hand, an alarm signal is issued through the display, and on the other hand, a stop-execution command is issued to the feed servo system to implement over-travel protection.
To sum up, the working principle of CNC machine tools can be summarized as follows: the computer in the NC device performs a series of processing on the information recorded through the input device by means of digital and character encoding, and then passes through the servo system and the programmable controller. The machine tool spindle and the feed and other actuators issue commands. The machine tool body follows these instructions and, with the help of the feedback device, performs various actions required for machining the workpiece, such as the movement path of the tool relative to the workpiece, the displacement amount, and the The speed and other items are required to achieve automatic control to complete the processing of the workpiece.