Basic concepts of NC machining programming

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Basic concepts of NC machining programming up to 2010

1 NC programming

the so-called NC programming is the whole process of recording the process, process parameters, machine tool movement, tool displacement and other information of parts on the program sheet in NC language and checking it. In order to distinguish from the internal program (system software) of CNC system and the part source program used for automatic programming, the program directly used for machining input from the outside is called NC machining program, which is called NC program for short

the program used by the NC machine tool is compiled in a certain 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 of the machine tool programming manual. When preparing the program, the programmer shall analyze the technical requirements, part geometry, dimensional accuracy requirements, etc. determined by the average and minimum values of the experimental results of the compressive strength and flexural strength levels in 7.5.3 of the drawing specification according to table 2, and determine the processing method and processing route; Carry out mathematical calculation and obtain tool path data; Then, according to the code and program format specified by the NC machine tool, the size of the workpiece to be processed, the trajectory of the tool motion center, cutting parameters and auxiliary functions (such as tool change, spindle forward and reverse rotation, cutting fluid switch, etc.) are compiled into a processing program, which is input into the NC system, and the numerical control system controls the machine tool to process automatically. The ideal numerical control program should not only ensure that the qualified workpiece that meets the requirements of the drawing can be processed, but also make the function of the numerical control machine tool be reasonably applied and give full play to, so that the numerical control machine tool can work safely, reliably and efficiently

2. NC programming method

NC programming has generally gone through several stages: machine language programming, battery with brand name of Alta pack is equipped with sheath program, high-level language programming, code format programming, man-machine dialogue programming and dynamic simulation. In the 1970s, the American Electronics Industry Association (EIA) and the international organization for Standardization (ISO) successively formulated a number of standards and specifications for the coordinate axis and movement direction of NC machine tools, the code, character and program segment format of NC program programming (China has also formulated corresponding national standards and ministerial standards according to ISO standards), thus codes and marking symbols appeared, NC machining source code format programming program written in strict format. This great progress in source programming technology is of far-reaching significance. After the emergence of this programming method, all CNC systems, regardless of grade, have programming functions. Because the programming process is greatly simplified, the machine operator can program as long as he looks up and carefully reads the system instructions. Thus, CNC machine tools are applied in a wide range of fields

NC programming methods are mainly divided into manual programming and automatic programming:

(1) manual programming

manual programming refers to the whole process of NC programming from part drawing analysis, process processing, numerical calculation, programming, until program verification. Manual programming is suitable for the preparation of processing programs for point processing or parts with less complex geometry, as well as occasions where the calculation of program coordinates is relatively simple, there are not many program segments, and the programming is easy to realize. This method is relatively simple, easy to master, and has strong adaptability. Manual programming method is the basis of compiling processing program and the main method of machine tool on-site processing and debugging. It is a basic skill that machine tool operators must master, and its importance cannot be ignored

(2) automatic programming

automatic programming refers to the process of automatically generating NC machining programs with the support of computers and corresponding software systems. It gives full play to the functions of computer fast calculation and storage. Its characteristic is to use simple and customary language to describe the geometry of the processing object. After all, the experimental equipment is metal products, processing technology, cutting parameters, auxiliary information and other contents according to the rules, and then the computer automatically carries out numerical calculation, tool center motion trace calculation, post-processing, generates the part processing program sheet, and simulates the processing process. For the parts with complex shape, non-circular curve contour, three-dimensional surface and other parts, the automatic programming method has high efficiency and good reliability. In the process of programming, the programmer can check whether the program is correct in time and modify it in time when necessary. Because the use of computers instead of programmers completes the tedious numerical calculation work and saves the workload of writing program sheets, it can improve the programming efficiency dozens of times or hundreds of times, and solve the programming problems of many complex parts that cannot be solved by manual programming

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