Compared with ordinary machine tools, CNC machining centers have high machining precision, good dimensional stability, low labor intensity, and are convenient for modern management. However, due to improper operation or programming errors, etc., it is easy for the tool or tool holder to hit the workpiece or the machine tool. cause personal accidents. Therefore, from the perspective of maintaining accuracy, the collision between the tool and the machine tool or workpiece is never allowed in the use of CNC machine tools. The reasons for the knife collision are summarized and analyzed below.
Because the CNC machining center is locked by software, when simulating machining, when the automatic operation button is pressed, it is impossible to visually see whether the machine tool is locked or not on the simulation interface. There is often no tool setting during the simulation. If the machine tool is not locked and running, tool collisions are very likely to occur. Therefore, before simulating processing, you should go to the running interface to confirm whether the machine tool is locked. Forgot to turn off the dry run switch during processing. Because during the program simulation, the dry run switch is often turned on in order to save time. Dry run means that all motion axes of the machine tool run at the speed of G00. If the air-running switch is not turned off during processing, the machine tool ignores the given feed rate and runs at the speed of G00, resulting in accidents such as knife hitting and machine tool collision. There is no return to the reference point after the dry run simulation. When verifying the program, the machine tool is locked, and the tool is running in simulation relative to the workpiece (the absolute and relative coordinates are changing). At this time, the coordinates do not match the actual position. The method of returning to the reference point must be used to ensure that the machine The zero coordinates are consistent with the absolute and relative coordinates. If the machining operation is carried out without finding any problems after checking the program, it will cause the collision of the tool. The direction of overtravel release is wrong.
When the machine tool is overtravel, press and hold the overtravel release button, and move in the opposite direction manually or manually to eliminate it. However, if the direction of release is reversed, it will cause damage to the machine tool. Because when the overtravel release is pressed, the overtravel protection of the machine tool will not work, and the travel switch of the overtravel protection is already at the end of the stroke. Add Xiaobian WeChat Yuki7557 to get the 10G CNC tutorial. At this time, the worktable may continue to move in the direction of overtravel, and eventually the screw will be broken, causing damage to the machine tool. Cursor position is incorrect when the specified line is run. When the specified line is run, it is often executed downwards from the position of the cursor. For lathes, it is necessary to call the tool offset value of the tool used. If the tool is not called, the tool in the running block may not be the desired tool, and it is very likely that the tool collision accident will occur due to different tools. Of course, on the machining center and CNC milling machine, the coordinate system such as G54 and the length compensation value of the tool must be called first. Because the length compensation value of each knife is different, if it is not called, it may cause knife collision.
As a high-precision machine tool, CNC machine tools are very necessary to avoid collisions. Operators are required to develop the habit of being careful and cautious, and operate the machine tools in the correct way to reduce the occurrence of machine tool collisions. With the development of technology, advanced technologies such as tool damage detection during processing, machine tool anti-collision detection, and machine tool adaptive processing have emerged, which can better protect CNC machine tools.
There are several reasons for the collision of the machining center:
1. The position of the spindle tool change point is wrong or has errors.
2. Spindle orientation error.
3. The mechanical claw of the tool magazine is not opened normally.
4. The wrong output of the tool magazine signal causes the tool program to be confused.
5. Program confusion caused by other interference signals of the machine tool.
Common knife collision phenomena can be summarized as follows:
One is the phenomenon of knife collision caused by programming errors.
The second is the phenomenon of knife collision caused by wrong machine parameter setting.
The third is the phenomenon of knife collision caused by improper operation of the machine tool.
Several Countermeasures to Prevent Tool Collision in NC Machining
In summary, there are 9 reasons:
(1) Programming errors
The process arrangement is wrong, the process succession relationship is not considered carefully, and the parameter setting is wrong.
Example: A. The coordinates are set to be zero at the bottom, but actually the top is 0;
B. The safety height is too low, so that the tool cannot be completely lifted out of the workpiece;
C. The secondary roughing allowance is less than that of the previous knife;
D. After the program is written, the path of the program should be analyzed and checked;
(2), program sheet remarks error
Example: A. The number of one-sided collisions is written as four-sided division;
B. The clamping distance of the vise or the protruding distance of the workpiece is marked incorrectly;
C. When the protruding length of the tool is unknown or wrong, it will cause a tool collision;
D. The program list should be as detailed as possible;
E. The principle of replacing the old with the new should be adopted when changing the program sheet: destroy the old program sheet.
(3) Tool measurement error
Example: A. The tool setting data input does not consider the tool setting bar;
B. The tool is installed too short;
C. Scientific methods should be used for tool measurement, and more accurate instruments should be used as much as possible;
D. The length of the installed knife should be 2-5mm longer than the actual depth.
(4), program transmission error
The program number is wrongly called or the program has been modified, but the old program is still used for processing;
On-site processors must check the detailed data of the program before processing;
For example, the time and date of programming, and simulated with bear family.
(5), wrong tool selection
(6), the blank exceeds expectations, the blank is too large and does not match the blank set by the program
(7), the workpiece material itself is defective or the hardness is too high
(8) Clamping factors, block interference and not considered in the program
(9) Machine tool failure, sudden power failure, lightning strike causing knife collision, etc.
