Many instructions often used by machining centers are the same as those of CNC machine tools, which will not be described here. Only some instructions reflecting machining center features are described below:
1. Accurate stop verification instruction G09
Instruction format: G09;
It can be used for machining parts with sharp edges and corners.
2. Tool offset setting command G10
Instruction format: g10p_ R_ ;
P: Command offset number; R: offset
Tool offset can be set by program setting.
3. Single direction positioning command G60
Instruction format: G60 x_ Y_ Z_ ;
10. Y and Z are the coordinates of the end point to be accurately located.
For hole machining that requires precise positioning, using this command can make the machine tool realize single direction positioning, so as to eliminate the machining error caused by reverse clearance. The positioning direction and overshoot are set by parameters.
4. Precise stop verification mode command G61
Instruction format: G61;
This instruction is modal instruction. In G61 mode, it means that every program contains G09 instruction.
5. Continuous cutting mode command G64
Instruction format: G64;
This command is a modal command and also the default state of the machine tool. After the tool moves to the end of the command, it will not slow down and continue to execute the next program segment, which will not affect the positioning or verification in G00, G60 and G09. G64 is used to cancel G61 mode.
6. Automatically return reference point instructions G27, G28, g29
(1) Return reference point verification instruction G27
Instruction format: G27;
10. Y and Z are the coordinate values of the reference point in the workpiece coordinate system, which can check whether the tool can be positioned on the reference point.
Under this command, the commanded axis moves back to the reference point quickly, decelerates automatically and makes positioning inspection at the specified coordinate value. If it is positioned to the reference point, the signal light of the axis reference point will be on; if it is inconsistent, the program will check again.
(2) Automatic return to reference point instruction G28
Instruction format: G28 x_ Y_ Z_ ;
10. Y and Z are coordinate values of intermediate point, which can be set arbitrarily. The machine moves to this point first and then returns to the reference point.
The intermediate point is set to prevent movement interference with workpiece or fixture when the tool returns to the reference point.
Example: N1 G90 x100.0 y200.0 z300.0
N2 G28 x400.0 y500.0; (middle point is 400.0500.0)
N3 G28 z600.0; (the middle point is 400.0500.0600.0)
(3) Automatically return g29 from reference point
Instruction format: g29 x_ Y_ Z_ ;
10. Y, Z are the returned end coordinates
In the return process, the tool moves from any position to the middle position determined by G28, and then moves to the end point. G28 and g29 are generally used in pairs, and G28 and G00 can also be used in pairs.
For example, as shown in Figure 5-7, after machining, the tool has been positioned to point a (100170), point B (200270) is taken as the middle point, and point C (500100) is the point to be reached when g29 is executed. The procedure is as follows:
G91 G28 X100. 0 Y100.0;
M06;
G29 X300.0 Y-170.0;
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