Differences and programming skills of several sets of commonly used instructions in CNC machining centers

With the development of science and technology and the advancement of society, people have higher and higher requirements on the performance and quality of products, so that the application of CNC machine tools has been popularized to a certain extent, and the high-performance and high-efficiency machining centers have gradually become the needs of the society. Through several years of practical application and teaching practice and exploration of the processing center, the author summarizes his own experience and experience, hoping to enlighten the readers.

1. Pause instruction

G04X(U)_/P_ refers to the tool pause time (feed stop, spindle does not stop), and the value after address P or X is the pause time. The value after X must have a decimal point, otherwise it is calculated as one thousandth of this value, in seconds (s), and the value after P cannot be represented by a decimal point (ie, an integer) in milliseconds (ms).
For example, G04 X2.0; or G04 X2000; pause 2 seconds G04 P2000;
However, in some hole machining instructions (such as G82, G88 and G89), in order to ensure the roughness of the bottom of the hole, a pause time is required when the tool is machined to the bottom of the hole. At this time, it can only be represented by the address P. The address X indicates that the control system considers X to be an X-axis coordinate value for execution.
For example, G82X100.0Y100.0Z-20.0R5.0F200P2000; drilling (100.0, 100.0) to the bottom of the hole for 2 seconds
G82X100.0Y100.0Z-20.0R5.0F200X2.0; Drilling (2.0, 100.0) to the bottom of the hole will not be suspended.

2. The difference and connection between M00, M01, M02 and M30

M00 is the program unconditional pause instruction. The program execution stops at this point and the spindle stops. Restart the program, you must first go back?
絁OG state, press CW (spindle forward rotation) to start the spindle, then return to the AUTO state, press the START button to start the program.
M01 is a program selective pause instruction. Before executing the program, you must open the OP STOP button on the control panel to execute. The effect after execution is the same as M00. Restart the program as above.
M00 and M01 are often used for inspection or chip removal of workpiece sizes in the middle of machining.
M02 is the main program end instruction. When this command is executed, the feed stops, the spindle stops, and the coolant closes. But the program cursor stops at the end of the program.
M30 is the main program end command. The function is the same as M02. The difference is that the cursor returns to the head position of the program, regardless of whether there are other blocks after M30.

3. Addresses D and H have the same meaning

The tool compensation parameters D and H have the same function and can be interchanged arbitrarily. They all represent the address names of the compensation registers in the CNC system, but the specific compensation values ​​are determined by the compensation address addresses behind them. However, in the machining center, in order to prevent errors, it is generally specified that H is the tool length compensation address, the compensation number is from 1 to 20, D is the tool radius compensation address, and the compensation number is from the 21st (the tool magazine of 20 knives).
For example, G00G43H1Z100.0;
G01G41D21X20.0Y35.0F200;

4. Mirror instruction

Mirror processing instructions M21, M22, M23. When only the X-axis or Y-axis is mirrored, the cutting sequence (cut milling and up-cut milling), the tool compensation direction, and the circular interpolation steering will be opposite to the actual program, as shown in Figure 1. When the X-axis and Y-axis are mirrored at the same time, the cutting order, the tool compensation direction, and the circular interpolation steering are unchanged.
Note: You must use M23 to cancel after using the mirror command, so as not to affect the following programs. In G90 mode, use the mirror or cancel command to return to the origin of the workpiece coordinate system before use. Otherwise, the CNC system cannot calculate the following motion trajectory, and there will be a chaotic phenomenon. At this time, manual home position return operation must be implemented to solve. The spindle steering does not change with the mirror command.
Figure 1 Tool compensation and smooth change when mirroring

5. Circular interpolation command

G02 is clockwise interpolation, G03 is counterclockwise interpolation, in the XY plane, the format is as follows: G02/G03X_Y_I_K_F_ or G02/G
03 X_Y_R_F_, where X and Y are the coordinates of the end point of the arc, I and J are the incremental values ​​of the starting point of the arc to the center of the circle on the X and Y axes, R is the radius of the arc, and F is the feed amount.
Note that in arc cutting, q≤180°, R is positive; q>180°, R is negative; I, K can also be specified by R. When both are specified, R command takes precedence, I , K is invalid; R can not do full circle cutting, full circle cutting can only be programmed with I, J, K, because through the same point, there are countless circles with the same radius, as shown in Figure 2.
Figure 2 When the circle passing through the same point has I and K is zero, it can be omitted; regardless of G90 or G91 mode, I, J, and K are all programmed according to relative coordinates; when circular interpolation is used, the tool compensation command G41/ cannot be used. G42.

6. Advantages and disadvantages between G92 and G54~G59

G54～G59 are the coordinate system set before machining, and G92 is the coordinate system set in the program. It is not necessary to use G92 when G54～G59 is used, otherwise G54～G59 will be replaced and should be avoided. Table 1 shows.
Table 1 Differences between G92 and working coordinate system Note: (1) Once G92 is used to set the coordinate system, then G54～G59 will not play any role unless the system is restarted after power off, or then the new one is set with G92. Workpiece coordinate system. (2) After the program using G92 ends, if the machine does not return?
紾92 set the origin, the program will be started again, the current position of the machine will become the new workpiece coordinate origin, prone to accidents. Therefore, I hope that the readers will use it with caution.

7. Prepare a tool change program.

At the machining center, tool change is inevitable. However, the machine tool has a fixed tool change point when it leaves the factory. It is not possible to change the tool position, and the tool compensation and cycle must be canceled before the tool change. The spindle stops and the coolant closes. There are many conditions. If you need to ensure these conditions before each manual tool change, it is not only error-prone but also inefficient. Therefore, we can compile a tool change program to save the low lining. The M98 call can complete the tool change at one time.
Take the PMC-10V20 machining center as an example. The procedure is as follows:
O2002; (program name)
G80G40G49 ; (Cancel fixed cycle, tool compensation)
M05; (spindle stop)
M09; (coolant off)
G91G30Z0; (Z axis returns to the second origin, ie the tool change point)
M06; (changing the knife)
M99; (subprogram end)
When you need to change the tool, just type "T5M98P2002" in the MDI state, you can replace the required tool T5, thus avoiding many unnecessary mistakes. The majority of readers can compile the corresponding tool change program according to the characteristics of their own machine tools.

8. other

The block sequence number is represented by the address N. Generally, the numerical control device itself has a limited memory space (64K). In order to save storage space, the program sequence number is omitted. N only indicates the block number, which makes it easy to find the editing program. It has no effect on the machining process. The sequence number can be incremented or decremented, and the value is not required to be continuous. However, it cannot be omitted when using some loop instructions, jump instructions, and calling subroutines and mirror instructions.

9. In the same block, the same instruction (same address character) or the same group of instructions will appear after the action.

For example, the tool change program, T2M06T3; replaced with T3 instead of T2;
G01G00X50.0Y30.0F200; G00 is executed (although there is an F value, G01 is not executed).
The instruction codes that are not in the same group have the same effect in the same sequence.
G90G54G00X0Y0Z100.0;
G00G90G54X0Y0Z100.0;
All of the above were run on the PMC-10V20 (FANUC SYSTEM) machining center. In practical applications, only a deep understanding of the usage and programming rules of various instructions.