Analysis and Treatment of Tool Change Fault in CNC Machining Center

1. Fault phenomenonWhen changing the knife, the manipulator is stuck and cannot change the knife. The position of the manipulator for changing the knife is offset, and the knife is changed.2 fault analysis and treatment

2.1 tool change principleThe machining center is a rotary tool magazine, and the tool change mechanism is cam type. The tool change process is as follows:(1) Write m06t01 to start the tool change and tool selection cycle.

(2) The spindle will stop at the oriented spindle stop point, the coolant stops, and the z-axis moves to the tool change position (second reference point).(3) Select the tool. After NC compiles it to PLC according to the t command, start selecting the tool. The tool magazine motor rotates and rotates the target tool number to the tool change point of the tool magazine. Note that the t command is the tool sleeve position of the tool magazine at this time.(4) The tool change motor drives the cam mechanism to rotate 90 from the parking position to grasp the tool in the effective tool sleeve and the tool in the spindle. At the same time, detect the change of the proximity switch state of the cam mechanism, the PMC output sends out the tool loosening command, the tool magazine tool sleeve tool loosening and the spindle tool loosening solenoid valve are powered on, the cam continues to rotate, drive the manipulator down, push down the tool handle and prepare for exchange. As shown in Figure 1.

(5) The manipulator rotates 180 to exchange the tool, the cam continues to move upward, install the tool into the spindle, and install the tool on the original spindle into the tool sleeve at the tool change position of the tool magazine. At the same time, the detection switch sends a tool tightening command to PMC, the solenoid valve loses power, the shaft tool handle is clamped, the butterfly spring retracts, and the spindle tool is clamped.(6) Change to the manipulator, continue to rotate 90 , and stop completing a set of tool change actions.2.2 fault analysis

Change the tool to the fourth step of 2.1. The tool change manipulator is stuck, and the spindle has been loosened for blowing, but the tool cannot be pulled out. Cut off the power and manually turn the tool change motor. After completing a tool change action, manually load and unload the tool, the action is normal, and the problems of spindle tightening tool are preliminarily eliminated. When the tool change process is performed again, the manipulator gets stuck and the manipulator claw at the tool magazine falls off. After the tool change is found, the manipulator installs the tool on the spindle and the position is offset, as shown in Figure 2.

After the tool is removed, it is found that the action is normal. The reason for this situation may be the offset between the manipulator and the spindle, or the deviation of the accuracy of the manipulator axis relative to the spindle axis, and the inaccurate positioning of the spindle will also lead to the offset of the tool change position. Implement the tool change action step by step, check the accurate positioning of the spindle, and eliminate the fault caused by inaccurate positioning. According to the table, the mechanicalThe axial position and rotation center distance of hand, knife sleeve and spindle are consistent, so the fault of mechanical jamming of mechanical mobile phone is also eliminated.

Recently, this machine tool mainly processes stainless steel and other material workpieces, with large cutting volume and heavy load. It runs under re cutting for a long time. It is found that the manipulator is not loose and the telescopic action of the manipulator claw is flexible. However, it is found that the adjustment block on the manipulator is worn. It is disassembled and observed that the adjustment block is mainly used to clamp the tool handle. After re repair and processing, try again, The offset disappears at the spindle position. The main cause of this fault is the large impact of the manipulator and frequent tool change, resulting in the loosening and wear of the clamping claw, as shown in Figure 3.