The working principle of CNC machine tools
CNC machine tool is an automatic machine tool equipped with a program control system. The control system can logically process programs with control codes or other symbolic instruction rules and decode them, so that the machine tool acts as a CNC bending machine and processes parts.
1. The machine tool body of the CNC machine tool is similar to the traditional machine tool, which is composed of the main shaft transmission equipment, feed transmission equipment, bed, operating table, auxiliary sports equipment, hydraulic and pneumatic system, smooth system, cooling equipment, etc. However, CNC machine tools have undergone great changes in the overall layout, appearance, transmission system, tool system structure and operation organization. The intention of this change is to satisfy the requirements of CNC machine tools and give full play to the characteristics of CNC machine tools. .
⑵ CNC unit
The CNC unit is the center of the CNC machine tool. The CNC unit consists of three parts: information input, processing and output. The CNC unit accepts digitized information, and after decoding, interpolation, and logic processing by the control software and logic circuit of the numerical control equipment, it outputs various command information to the servo system, and the servo system drives the fulfillment components for feed movement.
⑶Input / output device
The input device transfers various processing information to the external device of the computer. In the early days of CNC machine tools, the input device was perforated paper tape, which has been screened, and then developed into cassette tapes, and then into portable hardware such as keyboards and disks, which greatly facilitates information input operations. Now it is universal DNC network communication serial communication Method input.
Output refers to the output of internal operating parameters (including the original parameters of the machine under normal and aspirational operating conditions, fault diagnosis parameters, etc.). Generally, these parameters need to be output for record and preservation in the machine's initial operating conditions. After a period of operation, the output and the original The comparison and comparison of data can help to judge whether the machine tool operation is normal.
⑷Servo unit The servo unit is composed of a driver and a drive motor, and together with the fulfillment components and mechanical transmission components on the machine tool form a feed system for the CNC machine tool. Its function is to convert the pulse signal from the numerical control equipment into the movement of the moving parts of the machine tool. Regarding the stepper motor, each pulse signal causes the motor to rotate through a viewpoint, thereby driving the moving parts of the machine tool to move a small interval. Each performance component of the feed movement has a corresponding servo drive system, and the function of the entire machine tool depends primarily on the servo system.
⑸ Drive equipment The drive equipment converts the amplified command signal into mechanical motion, drives the machine tool through simple mechanical connection parts, makes the worktable accurately positioned or performs strict relative motion according to the regular trajectory, and finally processes the parts required by the drawing. Corresponding to the servo unit, the driving equipment includes stepper motor, DC servo motor and AC servo motor.
The servo unit and the drive equipment can be collectively referred to as the servo drive system. It is the power equipment for machine tool operations. The commands of the CNC equipment must be implemented by the servo drive system. Therefore, the servo drive system is an important part of the CNC machine tool.
Programmable controller (PC, Programmable Controller) is a general-purpose automatic control device based on a microprocessor, designed for application in industrial environments. Because the original intention of developing this kind of equipment was to deal with the logic and switch control of the produced equipment, it is called Programmable Logic Controller (PLC). When PLC is used to control the sequential actions of the machine tool, it can also be called a programmable machine controller (PMC, Programmable Machine Controller). PLC has become an indispensable control device for CNC machine tools. CNC and PLC work together in harmony to complete the control of CNC machine tools.
⑺Measurement response equipment
Measurement equipment is also called response element, including grating, rotary encoder, laser rangefinder, magnetic grid, etc. It is usually installed on the working table or screw of the machine tool. It converts the actual displacement of the working table of the machine tool into an electrical signal and reacts it to the CNC device. The CNC device compares the command value with an error signal to control the machine tool to move in the direction of eliminating the error .
2. Operation principle
When using a CNC machine tool, first of all, the geometric information and process information of the processed part drawing must be written into a processing program with regular codes and formats; then the processing program is input to the CNC equipment, and processed and distributed through the CNC system information according to the requirements of the program To move each coordinate by a few minimum displacements to realize the relative movement of the tool and the workpiece and complete the processing of the parts.