CNC machining is a high-precision and high-efficiency machining method in which automatic machine tools use digital information to control the displacement of parts and tools. It is an effective way to solve the problems of a large variety of aerospace products and parts, small batches, complex shapes and high precision, and to achieve efficient automatic processing. Next, let's take a look at the composition and working steps of CNC machine tools.

1. The composition of CNC machine tools. CNC machine tools are composed of programs, input and output devices, CNC units, servo systems, position feedback systems and machine tool bodies. The following is a brief introduction.

1. Numerical control unit. The CNC unit is the core of the CNC machine tool, which consists of three parts: information input, processing and output.

The numerical control unit receives the digitized information, and after decoding, interpolation and logic processing by the control software and logic circuit of the numerical control device, outputs various instruction information to the servo system, and the servo system drives the execution components for feeding motion. Others include speed change, reversing and start/stop signals of main moving parts; tool command signals for selecting and exchanging tools, start and stop of cooling and lubrication, loosening and clamping of workpieces and mechanical parts, indexing table indexing and others Auxiliary command signal, etc.

2. Servo system. It consists of a driver and a drive motor, and together with the executive components and mechanical transmission components on the machine tool constitute the feed system of the CNC machine tool. Its function is to convert the pulse signal of the numerical control device into the movement of the moving parts of the machine tool. In the case of stepper motors, each pulse signal turns the motor by an angle, which then drives the moving parts of the machine tool to move a small distance. Each execution part of the feed movement has a corresponding servo drive system, and the performance of the entire machine tool mainly depends on the servo system.

3. Position feedback system. Servo motor angular displacement feedback and CNC machine tool actuator (table) displacement feedback. Including gratings, rotary encoders, laser rangefinders, magnetic gratings, etc. The feedback device converts the detection results into electrical signals and feeds them back to the numerical control device. Through the comparison, the deviation between the actual position and the command position is calculated, and the deviation command is sent to control the feeding movement of the executing part.

4. The mechanical part of the machine tool. For the CNC machine tools of the machining center, there are also tool magazines for storing tools, manipulators for exchanging tools and other components. The mechanical components of CNC machine tools are similar to those of ordinary machine tools, but the transmission structure requirements are simpler, and the requirements for accuracy, rigidity and shock resistance are higher, and the transmission and speed change systems are more convenient to achieve automatic expansion.

Second, the working steps of CNC machine tools. In the process of CNC lathe processing should go through the following steps:

1. Preparation stage. According to the drawings of the machined parts, determine the relevant machining data (tool path coordinate points, machining cutting parameters, tool size information, etc.). And select other auxiliary information according to the process plan, selected fixture and tool type.

2. Programming phase. According to the machining process information, write the CNC machining program (description of machining process) in the language that the CNC system of the machine tool can recognize, and fill in the program list.

3. Prepare the information carrier. Based on the compiled program listings, the programs are stored on an information carrier (punched tape, magnetic tape, disk, etc.). All processing information is transmitted to the numerical control system through the information carrier. If the CNC machine is connected to a computer, the information can be loaded directly into the CNC system.

4. Processing stage. When the CNC system of the machine tool executes the program, it decodes and calculates the processing program statements, converts them into action instructions, and drives the moving parts. Under the unified coordination of the system, the moving parts are driven to move in time, and the workpiece is automatically processed.