Shandong Deed Precision Machine Tool Co., Ltd.
Shandong Deed Precision Machine Tool Co., Ltd.

Reason Analysis of Tool Collision Failure in CNC Milling Machine

Compared to traditional machines, CNC machining centers have higher precision, better dimensional stability, lower labor intensity, and are easy to manage with modern technology. However, due to incorrect operation or programming errors, the tool or tool holder can collide with the workpiece or machine, causing minor damage to the tool and part being processed, and major damage to machine components, compromising machining precision and potentially causing personal injury. Therefore, from a precision perspective, it is absolutely not allowed for the tool and machine or workpiece to collide in CNC machine operations. Below is a summary and analysis of the reasons for tool collisions.

Locking the machine on a CNC milling machine

Since the CNC machining center is locked with software, when simulating the machining process, it is not always clear whether the machine is locked when the automatic running button is pressed. Often, there is no tool setting during simulation. If the machine is not locked during operation, tool collision can easily occur. Therefore, before simulating the machining process, it is necessary to check whether the machine is locked in the operating interface. It is also important not to forget to turn off the dry-run switch during machining.

Forgetting to turn off the dry-run switch on a CNC milling machine during operation

During program simulation, the dry-run switch is often turned on to save time. This means all motion axes of the machine move at G00 speed during the dry-run, ignoring the specified feed rate. If the dry-run switch is not turned off during operation, the machine will move at G00 speed, causing tool and machine accidents. It is important to return to the reference point after the dry-run simulation.

Failure to return to the reference point after dry-run simulation on a CNC milling machine

When verifying programs, the machine does not move, while the tool relative to the workpiece moves during the simulation run (absolute and relative coordinates are changed). At this time, the coordinate does not match the actual position, so it is necessary to return to the reference point to ensure that the mechanical zero coordinate is consistent with the absolute and relative coordinates. Failure to discover the problem and proceeding with the machining operation can cause tool collisions.

Incorrect direction of over-travel release on a CNC milling machine

When the machine encounters over-travel, the over-travel release button should be pressed, and the machine should be moved in the opposite direction by manual operation or hand wheel to resolve the issue. However, if the direction of release is reversed, it can cause damage to the machine. When the over-travel release is pressed, the over-travel protection function of the machine will not work, and the travel switch has reached the end of the travel. This can cause the worktable to move in the over-travel direction, ultimately breaking the screw, damaging the machine.

Improper cursor position when running specified lines on a CNC milling machine

When running specified lines, it often starts from the cursor position and proceeds downward. For lathes, it is necessary to call the tool offset value. If the tool is not called, the tool used in the program segment may not be the desired tool, which can lead to tool collisions. 

Of course, it is important to call the coordinate system and the tool length compensation value before operating on machining centers and CNC milling machines. Since application of CNC machine tools have different length compensation value, not calling them can also cause tool collisions.

CNC machining centers are high-precision machines, and the prevention of tool collisions is very important. Operators should develop a conscientious and careful attitude, operate the machine properly, and reduce the occurrence of tool collisions. With the development of technology, advanced technologies such as tool damage detection, machine collision detection, and machine adaptive processing can better protect CNC machines.