1. Structure of CNC milling program
A complete CNC milling program consists of three parts: the beginning of the program, the contents of the program, and the end of the program.
(1) The beginning of the NC milling program The program number is the beginning of the program, and it is also the start marker of the program for searching and calling in the program directory in the memory of the numerical control device. The program number is generally composed of an address code and a four-digit number. Common program-defined address codes are O, P, or %. (2) Program content Program content is the main part of the entire program and consists of several program sections. Each program segment consists of several words, each consisting of an address code and several numbers. An instruction word represents a unit of information that represents a position or an action of a machine tool. (3) The end of the program The end of the program generally consists of the auxiliary function code M02 (end of program instruction) or M30 (end of program instruction and return program start instruction).2. The meaning of the words in the program section
(1) Block format
The block format refers to the rules for writing words, characters and data in a block. At present, the word address programmable format is commonly used. It consists of a statement word, a data word, and a program end symbol. The prefix of each word is an English letter, which is called the word address code. The word address code programmable section format is shown in the following table.Common forms of table segments
N156
G
G
X
Y
Z
A
B
C
F
M
Word address code programmable section format is characterized by: the order of the respective sequence in the program segment is not strict, the unnecessary words and the same continue with the previous block can be omitted; each program segment can have Multiple G commands or G codes; data words can be more or less, the program is short, intuitive, not error-prone, and thus widely used. (2) Block number abbreviation sequence number It is usually represented by numbers. The symbol N is also prefixed to the number. Many modern CNC systems do not require a block number, and the block number can be omitted. (3) Preparation function The preparation function is abbreviated as the G function, which consists of the preparation function address character G and numbers. For example, the linear interpolation command G01 and the G instruction code have been standardized. The G code indicates the preparation function. The purpose is to pre-set the control system to some expected state, or to a certain machining mode and state. For example, G00 presets the machine to the fast motion state. The preparation function indicates its own meaning. The G code will cause the controller to accept the programming instruction after the G code in a special way. (4) Coordinate character The coordinate word is composed of coordinate address characters and numbers, and is arranged in a certain order. Each group number must have the address character X, Y, Z as the address code. The address characters of each coordinate axis are arranged in the following order. X, Y , Z, U, V, W, P, Q, R, A, B, C, where X, Y, Z are the end coordinates of the tool motion. The program segment will indicate whether the coordinate value is absolute or incremental and is imperial or metric. The movement to the target position is either rapid or linear. (5) Feed function F The feed function consists of feed address characters F and numbers, the number indicating the selected feedrate. (6) Spindle speed function S The spindle speed function consists of the spindle address character S and numbers. The number indicates the spindle speed in rpm. (7) Tool function T The tool function consists of address characters T and numbers to specify the tool number. (8) Auxiliary functions The auxiliary function is abbreviated as M function and consists of auxiliary operation address characters M and numbers. (9) Block end symbol The block end symbol is placed after the last useful character of the block and indicates the end of the block. Because the control is different, the terminator should be defined according to the programming manual. It should be noted that there are many international standards for the format of CNC machine tools. With the development of numerical control machine tools, their system functions are more powerful and more convenient to use. There are certain differences in program format between different numerical control systems. Therefore, it is necessary to carefully understand the programming of a numerical control system when a specific numerical control machine tool is mastered. format.Polyester Polyol For Elastomer
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