Why do CNC machining centers bump knives?

It is said that in the career of a machine tool worker, no matter how careful it is, it is impossible to avoid a knife collision accident.This has nothing to do with whether the worker is serious and practical and stable, just like a person can not avoid mistakes in the growth process, in the growth process of a machine tool worker, the knife seems to be a hurdle that cannot be bypassing.

Bumping tool, refers to the tool in the process of moving with the workpiece, chuck or tailstock accidental collision machine accident, is the most likely accident for CNC lathe operation novices.

Knife collision will cause workpiece scrap, tool damage, serious damage to the accuracy of the machine tool, destroy the machine parts, and even endanger the personal safety of the machine tool processing personnel.

The occurrence of knife collision accidents is mainly caused by programming errors in the programming process or workers' operational errors in the processing link.

For workers, the general programming link is not easy to make mistakes, and many people have knife collision accidents, often caused by mistakes in the process of machine tool operation.

Because the CNC machining center is locked by software, in the simulation processing, when the automatic operation button is pressed, it is not intuitive to see whether the machine is locked in the simulation interface.

There is often no tool in the simulation, and if the machine tool is not locked to run, it is easy to bump the knife.

Therefore, before the simulation processing should go to the running interface to confirm whether the machine is locked.

1. Forget to turn off the empty running switch during processing.

Because in the program simulation, in order to save time, the empty run switch is often turned on.

Empty operation means that all moving axes of the machine are running at the speed of G00.

If the operation switch is not turned off during the processing time, the machine tool ignores the given feed speed, and runs at the speed of G00, resulting in knife and machine tool accidents.

2. No reference point is returned after running the simulation empty.

In the verification program when the machine is locked motionless, and the tool relative to the workpiece processing in the simulation operation (absolute coordinates and relative coordinates change), then the coordinates do not match the actual position, must use the method of returning the reference point to ensure that the mechanical zero coordinates are consistent with the absolute and relative coordinates.

If the machining operation is carried out without finding the problem after the verification procedure, it will cause the collision of the tool.

3. The direction of overshoot release is not correct.

When the machine overruns, it should press and hold the overruns release button, and move in the opposite direction manually or by hand, that is, it can be eliminated.

However, if the direction of lifting is reversed, it will cause damage to the machine tool.

Because when the overrange release is pressed, the overrange protection of the machine tool will not work, and the stroke switch of the overrange protection is already at the end of the stroke.

At this time, it is possible to cause the workbench to continue to move in the direction of excess, and eventually pull the lead screw, causing damage to the machine tool.

4. The cursor position of the specified line is incorrect.

When a specified line is run, it is usually executed downward from the cursor position.

For the lathe, it is necessary to call the tool offset value of the tool used, if the tool is not called, the tool running the program segment may not be the desired tool, and it is very likely to cause a collision accident due to 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 knife.

Because the length compensation value of each knife is not the same, it is possible to cause knife collision if it is not called.

As a high-precision machine tool, anti-collision is very necessary, requiring the operator to develop the habit of being careful and careful, operating the machine tool according to the correct method, and reducing the occurrence of machine tool collision.

With the development of technology, advanced technologies such as tool damage detection, machine tool anti-impact detection, and machine tool adaptive processing have emerged during processing, which can better protect CNC machine tools.

There are 9 reasons for this:

(‍1) Programming error

The process arrangement is wrong, the process undertaking relationship is not carefully considered, and the parameter setting is wrong.

Example :

A. The coordinate is set to zero at the base, but the top is 0 in practice;

B. The safety height is too low, resulting in the tool can not completely lift out the workpiece;

C. The second opening margin is less than the previous knife;

D. After the program is written, the path of the program should be analyzed and checked;

(2) Program single remarks error

Example:

A. The number of unilateral touches is written in four sides;

B. The clamping distance of the vise or the protruding distance of the workpiece is wrong;

C. The extension length of the tool is unknown or wrong, resulting in knife collision;

D. Procedure sheet should be as detailed as possible;

E. The principle of new for old should be adopted when the procedure is changed:Destroy the old program.

(‍3) Tool measurement error

Example:

A. The tool bar is not considered in the tool data input;

B. The tool is too short;

C. Tool measurement should use scientific methods, as far as possible with more accurate instruments;

D. The length of the tool should be 2-5mm longer than the actual depth.

(4) Program transmission error

Program number call error or program modification, but still use the old program processing; The site processor must check the detailed data of the program before processing; For example, the time and date the program was written and simulated with bear.

(5) Wrong knife selection

(6) the blank exceeds expectations, and the blank is too large and does not conform to the blank set by the program

(7) The workpiece material itself has defects or high hardness

(8) clamping factors, pad interference and the procedure is not considered

(‍9) Machine tool failure, sudden power failure, lightning strike caused tool collision, etc

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