First, the input device
The function of the input device is to transfer and store the NC code on the program carrier (information carrier) into the CNC system. The input device may be an opto-electronic reader, a tape drive or a floppy disk drive, etc., depending on the control storage medium. The CNC machine tool processing program can also be directly input into the CNC system through the keyboard manually; the CNC machining program can also be transferred to the CNC system by the programming computer using RS232C or by network communication.
There are two different ways to input the part program: one is to read the edge while processing (when the CNC system has a small memory), and the other is to read the part processing program into the memory inside the CNC device at one time. The internal memory is called up by piece by piece for processing.
Second, the numerical control device
The numerical control device is the core of the CNC machine tool. The numerical control device takes out one or several pieces of numerical control machining program sent from the internal memory or receives the numerical control processing program sent by the input device, and after compiling, calculating and logic processing by the logic circuit or system software of the numerical control device, outputs various control information and instructions, and controls the machine tool. The work of each part is to make the specified orderly movements and movements.
The contour of a part is often composed of a straight line, an arc or other non-arc curve. The tool must be moved according to the shape and size of the part during the machining process, that is, moved according to the graphic path. However, the input part processing program can only be the data of the starting point and the end point coordinate value of each line segment trajectory, which cannot meet the requirements. Therefore, the trajectory interpolation is performed, that is, the data point is densely defined between the starting point and the ending point coordinate value of the line segment. The coordinate values of a series of intermediate points are obtained, and a pulse signal is output to the corresponding coordinates, and the feed speed, the feed direction, the feed displacement amount, and the like of each coordinate axis (ie, each actuator of the feed motion) are controlled.
Third, the drive device and position detection device
The driving device accepts the command information from the numerical control device, and after power amplification, drives the moving parts of the machine tool in strict accordance with the requirements of the command information to process the parts that meet the requirements of the drawing. Therefore, its servo accuracy and dynamic response performance are one of the important factors affecting the machining accuracy, surface quality and productivity of CNC machine tools. The drive unit consists of a controller (including a power amplifier) and an actuator. At present, DC or AC servo motors are mostly used as actuators.
The position detecting device detects the actual displacement amount of each coordinate axis of the numerical control machine tool, and after inputting the feedback system to the numerical control device of the machine tool, the numerical control device compares the actual displacement amount value fed back with the set value, and controls the driving device to follow the command setting. Fixed value exercise.
Fourth, auxiliary control device
The main function of the auxiliary control device is to receive the switching quantity command signal output by the numerical control device, after compiling, logically discriminating and moving, and then driving the corresponding electric appliance after power amplification, driving the mechanical, hydraulic, pneumatic and other auxiliary devices of the machine tool to complete the instruction. Switching action. These controls include shifting, reversing and starting and stopping commands for the moving parts of the spindle, tool selection and exchange commands, cooling, starting and stopping of the lubrication device, loosening and clamping of the workpiece and machine components, indexing table indexing and indexing Wait for the switch to assist the action.
Because the programmable logic controller (PLC) has the characteristics of fast response, reliable performance, easy to use, program and modify the program and can directly start the machine switch, it has been widely used as an auxiliary control device for CNC machine tools.
