Programming and program carrier

NC program is the work instruction of NC machine tool to automatically process parts. Based on the process analysis of the machined parts, the relative position of the part coordinate system on the machine tool coordinate system, that is, the installation position of the parts on the machine tool is determined; Dimension parameters of the relative motion between the tool and the part; The process route of part processing, the process parameters of cutting and the action of auxiliary devices, etc. After obtaining all processing information such as motion, dimension, and process parameters of the parts, the NC program sheet for part processing shall be prepared with the standard NC code composed of words, numbers, and symbols according to the specified method and format. Programming can be done manually; For parts with complex shapes, automatic programming (APT) or cad/cam design should be carried out on a special programming machine or general-purpose computer.

The compiled numerical control program is stored on a storage carrier that is convenient for input to the numerical control device. It can be perforated paper tape, magnetic tape, magnetic disk, etc. which storage carrier is used depending on the design type of the numerical control device.

Input device

The function of the input device is to transfer the NC code to the program carrier (information carrier) and store it in the NC system. According to the different control storage media, the input device can be an optical reader, a magnetic tape drive, or a floppy disk drive. The NC machine tool processing program can also be manually input into the NC system through the keyboard; The NC machining program can also be transmitted to the NC system by the programming computer with RS232C or by network communication.

There are two different ways to input the part processing program: one is to read in while processing (the memory of the CNC system is small), and the other is to read all the part processing programs into the internal memory of the CNC device at one time, and then call them out from the internal memory section by section for processing.

Numerical control device

The numerical control device is the core of a numerical control machine tool. The NC device takes out from the internal memory or accepts one or more NC processing programs sent by the input device. After the logic circuit or system software of the NC device compiles, calculates, and logically processes, it outputs various control information and instructions to control the work of each part of the machine tool and make it perform the specified orderly movement and action.

The contour of a part is often composed of straight lines, arcs, or other non-circular curves. The tool must move according to the requirements of the shape and size of the part in the machining process, that is, move according to the graphic path. However, the input part processing program can only be the coordinate values of the starting and ending points of the track of each line segment, which can not meet the requirements. Therefore, track interpolation is required, that is, the "densification of data points" is carried out between the coordinate values of the starting and ending points of the line segment, the coordinate values of a series of intermediate points are calculated, and pulse signals are output to the corresponding coordinates to control the feed speed of each coordinate axis (i.e. each actuator of the feed movement) Feed direction and feed displacement, etc.

Driving device and position detection device

The driving device receives the command information from the numerical control device. After power amplification, it 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 drawing requirements. Therefore, its servo accuracy and dynamic response performance are the important factors that affect the machining accuracy, surface quality, and productivity of CNC machine tools. The driving device 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 detection device detects the actual displacement of each coordinate axis of the NC machine tool. After it is input to the NC device of the machine tool through the feedback system, the NC device compares the actual displacement value fed back with the set value, and controls the driving device to move according to the command set value.

Auxiliary controls

The main function of the auxiliary control device is to receive the switching value command signal output by the numerical control device, drive the corresponding electrical appliances after compilation, logic discrimination, and movement, and then power amplification, to drive the mechanical, hydraulic, pneumatic and other auxiliary devices of the machine tool to complete the switching value action specified in the command. These controls include speed change, reversing and start/stop commands of spindle moving parts, tool selection, and exchange commands, start/stop of cooling and lubrication devices, and loosening and clamping of the workpiece and machine tool parts, indexing worktable indexing, and other switch auxiliary actions.

Because programmable logic controller (PLC) has the characteristics of fast response, reliable performance, easy to use, program and modify programs, and can directly start the machine switch, it has been widely used as the auxiliary control device of CNC machine tools.

Machine tool body

The main body of the CNC machine tool is similar to the traditional machine tool, which is composed of the spindle transmission device, feed transmission device, bed, workbench, auxiliary motion device, hydraulic pneumatic system, lubrication system, cooling device, etc. However, great changes have taken place in the overall layout, appearance modeling, transmission system, tool system structure, and operating mechanism of CNC machine tools. The purpose of this change is to meet the requirements of CNC machine tools and give full play to CNC machine tools.

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