Technical column

Reasons for Knife Collision in 17 and 9 CNC Machining Centers


Compared with ordinary CNC machine tools, CNC machine tools have high processing accuracy, good dimensional stability, low labor intensity, and are convenient for modern management. However, due to improper operation or programming errors, it is easy to make the tool or tool holder collide with the workpiece or machine tool. The lighter one will crash the tool and the processed parts, the heavier one will damage the machine tool parts, so that the processing accuracy of the machine tool will be lost, and even cause personal accidents. Therefore, from the point of view of maintaining accuracy, tool collision with machine tool or workpiece must not be allowed in the use of NC machine tools. The reasons for the collision knife are summarized and analyzed below.

Cause analysis

1. Uncertainty of latch-up of machine tool

Because CNC Machining Center is locked by software, it is not intuitive to see whether the machine tool has been locked in the simulation interface when the automatic operation button is pressed. In simulation, there is often no tool alignment. If the machine tool is not locked in operation, it is very easy to collide with the tool. So before the simulation processing, we should go to the operation interface to confirm whether the machine tool is locked. Forget to turn off the empty switch during processing.

2 Unchecked Air Operating Switch

In order to save time, the air-operated switch is often turned on when the program is simulated. Empty running means that all moving axles of machine tools run at G00 speed. If the switch is not switched off, the machine tool ignores the given feed speed and runs at G00 speed, resulting in knife punching and machine collision accidents. No reference point was returned after air operation simulation. In the checking program, when the machine is locked and the tool is running in simulation (absolute coordinates and relative coordinates are changing) relative to the workpiece, the coordinates do not match the actual position. The method of returning the reference point must be used to ensure that the zero coordinates of the machine are consistent with the absolute and relative coordinates. If the problem is not found after the verification procedure, the machining operation will cause tool collision.

3. The direction of override relief is not right

When the machine tool is out of range, it should press the release button and move in the opposite direction manually or manually, which can be eliminated. But if the direction of relief is reversed, it will cause damage to the machine tool. Because when the overrun is relieved, the overrun protection of the machine tool will not work, and the overrun switch is already at the end of the trip. At this time, it may cause the worktable to continue to move in the direction of overrun, eventually pull the lead screw, resulting in machine tool damage. The cursor position is inappropriate when the specified row is running. When a specified line is running, it is often performed downward from where the cursor is located. For a lathe, it is necessary to call the tool deviation of the tool used. If the tool is not called, the tool running in the program section may not be the required tool, and it is very likely to cause tool collision accidents because of the different tools. Of course, in the machining center, CNC milling machine must first call the coordinate system such as G54 and the length compensation value of the cutter. 

Because the length compensation value of each knife is different, if not invoked, it may also cause a collision knife.

To sum up, there are nine reasons:

1 programming error

2 Program Single Note Error

3 Tool Measurement Error

4 Program Transfer Error

5. Error in tool selection

6. The blank exceeds the expectation, and the excessive blank is not consistent with the blank set by the program.

7 Workpiece material itself is defective or too hard

8 clamping factors, pad interference and not considered in the program

9 Machine tool failure, sudden power failure, lightning strike leading to knife impact, etc.

CNC Machining Center CNC machine tool as a high precision machine tool, anti-collision is very necessary, requiring operators to develop the habit of careful and cautious, according to the correct method to operate the machine tool, reduce the phenomenon of machine tool collision. With the development of technology, advanced technologies such as tool damage detection, machine tool anti-collision detection and machine tool self-adaptive processing have emerged, which can better protect CNC machine tools.

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