The basic concept of CNC machining programming

1. NC programming

The so-called numerical control programming is to record the process of the part, the process parameters, the movement of the machine tool and the amount of tool displacement in the NC language on the program list, and the entire process is checked. In order to distinguish it from the internal program (system software) of the numerical control system and the part source program for automatic programming, the program directly input for processing from the outside is called a numerical control machining program, which is simply referred to as a numerical control program.

The programs used in CNC machine tools are programmed in a format and in the form of code. There are many kinds of numerical control systems, and the language rules and formats of the numerical control programs they use are also different. The programming should be carried out in strict accordance with the provisions in the machine programming manual. When programming, the programmer should analyze the technical requirements specified by the drawings, the geometry of the parts, the dimensional accuracy requirements, etc., determine the processing method and processing route; perform mathematical calculations to obtain the tool path data; then press the code specified by the CNC machine tool and The program format, the workpiece size, tool movement center trajectory, cutting parameters and auxiliary functions (such as tool change, spindle forward and reverse, cutting fluid switch, etc.) information into a machining program, and input into the CNC system, controlled by the CNC system The machine tool automatically processes. The ideal NC program should not only ensure that qualified workpieces can meet the requirements of the drawings, but also make the functions of the CNC machine tools properly applied and fully utilized, so that the CNC machine tools can work safely, reliably and efficiently.

2. CNC machining program

CNC programming has gone through several stages such as machine language programming, high-level language programming, code format programming, and human-machine dialog programming and dynamic simulation. In the 1970s, the Electronic Industry Association (EIA) and the International Organization for Standardization (ISO) developed several standards and specifications for the axes and motion directions of CNC machine tools, the code, character and block format for NC programming. China has also developed corresponding national standards and ministerial standards in accordance with ISO standards, resulting in the use of code and marking symbols, according to the strict format of the CNC machining source program - code format programming program. This significant advancement in the development of source technology is extremely significant. After this programming method appears, all CNC systems have programming functions regardless of the grade. Because the programming process is greatly simplified, the machine operator has the ability to program by simply reviewing and perusing the system instructions. This makes CNC machine tools go to a wide range of applications.

CNC machining program programming methods are mainly divided into manual programming and automatic programming:

(1) Manual programming

Manual programming refers to the whole process of numerical control programming from parts drawing analysis, process processing, numerical calculation, writing program list, and program checking. Manual programming is suitable for writing machining programs for point machining or parts with less complex geometries, as well as occasions where program coordinate calculation is simple, there are not many program segments, and programming is easy to implement. This method is relatively simple, easy to grasp, and adaptable. The manual programming method is the basis for programming and is the main method for machine tool processing and debugging. It is a basic skill that must be mastered by machine tool operators. Its importance cannot be ignored.

(2) Automatic programming

Automatic programming refers to the process of automatically generating a CNC machining program with the support of a computer and a corresponding software system. It takes full advantage of the computer's fast computing and storage capabilities. The characteristic is that the geometry, processing technology, cutting parameters and auxiliary information of the processing object are described according to rules in a simple and customary language, and then the computer automatically performs numerical calculation, tool center motion trajectory calculation and post processing. A part program list is generated and the machining process is simulated. For parts with complex shapes, non-circular contours, three-dimensional surfaces, etc., the automatic programming method is efficient and reliable. During the programming process, the programmer can check whether the program is correct and can be modified in time. Because the computer is used instead of the programmer to complete the cumbersome numerical calculation work, and the workload of writing the program list is saved, the programming efficiency can be improved by several times or even hundreds of times, and the programming problem of many complicated parts which cannot be solved by manual programming is solved. .