1 Introduction
In the NC machining program code, there is a mirror processing instruction. For example, the image processing command of a certain type of machining center is G73 (schematic diagram is shown in Fig. 1). The original processing pattern is G72 in the first quadrant. After the G73 X-1 command is used, the graph shown in the second quadrant can be processed. . In other words, the machining code of the original block is axially mirrored on the Y-axis or the X-axis (or XY-mixed). When you want to process the mirror image, you do not need to program another program. You only need to mirror the original program code.
figure 1
CNC lathes are divided into left cutters and right cutters. The numerically controlled cutters are also divided into two tangential directions. In fact, the left-right tangential numerically-controlled cutter is a complete mirror image. It only needs to program the right cutter. The left cutter processing program can be completed using mirror processing. However, in the processing process, it is not simple to use mirroring instructions, and certain adjustments must be made to certain parts of the original program segment.
2. Precautions when using mirror processing
Mirroring changes the CW milling. As shown in FIG. 2 , the crest milling in the first quadrant is mirrored and then turned into the inverse milling state in the second quadrant, and vice versa. In order to obtain the surface finish of the mirror-machined workpiece surface that is the same as that of the body, it is necessary to reverse the original program's milling state before using the mirror image processing. Our common practice is to use crush milling in the original program. To mirror the reverse tool, change the original program to reverse milling. After mirroring, the reverse tool will also be crush.
figure 2
In the processing of five coordinates, we must also pay attention to the changes in A and B coordinates. As shown in Fig. 3, the main axis of the tool is parallel to the Y axis, the plane processed by the body is ΔEFG, and the plane mirrored by the Y axis YOZ is ΔE'F'G'. When processing ΔEFG, firstly, Rotate the q-angle around the Y-axis in the opposite direction (the rotation direction obeys the Cartesian coordinate system law, this time the B-coordinate is -q), and rotate the g-angle in the opposite direction around the newly formed X-axis EG (at this time, the A coordinate changes For -g), ΔEFG is placed at the machining position perpendicular to the Y axis, so the corresponding A and B coordinates are: A=-g, B=-q; and the mirror plane ΔE'F'G' is When machining, it is necessary to first turn the q′ angle around the positive direction of the Y axis, and then turn the g′ angle in the opposite direction around the newly formed X axis G′E′. The ΔE'F'G' is also placed at the processing position perpendicular to the Y axis. At this time, the corresponding A and B coordinates are: A=-g, B=q. From the above analysis, it can be seen that when the spatial plane mirrored by the Y-axis plane YOZ is mirrored at the five-axis machining center, the B coordinate must be Becomes the opposite value, and the A coordinate remains unchanged. Therefore, when machining the reverse tangential body using the mirror machining instruction, the B coordinate in the original tangential body program should be changed to the reversed value first. Some high-performance control systems can use the G73 X-1 B-1 instructions to change the X and B coordinates simultaneously.
image 3
The coordinate rotation direction in the mirroring process also changes. As shown in FIG. 4 , the coordinate system of the first quadrant is rotated around the Z-axis by the angle j, and after mirroring the Y-axis, it is reflected in the original coordinate system and becomes the -j angle around the Z-axis. Therefore, when mirror processing is used, It is necessary to change the coordinate rotation instruction in the original program.
Figure 4
To verify the safety distance when the machine tool retracts. The position of the retracting tool in the original program must have been verified, but the retracted points after mirroring need to be adjusted, especially after the translation and rotation of the five-axis machining additional coordinate system. Do a check to ensure the safety of the machine.
The above-mentioned situations we have encountered in the processing of the tangential cutting tool, as long as the mirror can be carefully analyzed before processing, and then make appropriate adjustments to the original program, you can quickly and accurately Another tangential cutter body is machined. In addition, mirroring can also be used in program adjustments between different CNC machine tools or in CAM software post-processing. It can reduce errors that may be caused by redefining the spindle of the machine or modifying the program. In short, in the current situation where CNC machining is generally still under manual programming, effective and reasonable use of mirror processing can greatly save programming time.