Repair methods for Spindle faults of XK713 Huazhong CNC Sharpening Bed

Abstract: The fault characteristics, structure and working principle of the spindle of the XK713 Huazhong CNC sharpening machine are analyzed. The causes of spindle faults are analyzed and the maintenance methods are introduced.

1. Characteristics of spindle failure

During the operation of the XK713 Huazhong CNC milling machine, the common fault characteristics of the spindle system mainly manifest in three aspects:

(1) The tool changing mechanism is stuck, and the tool cannot be removed from the spindle.

(2) The spindle can operate normally without tool clamping, but it does not operate after tool clamping is installed.

(3) During normal processing, the spindle often stops working and the processing automatically ends.

2 Main shaft structure and working principle

The spindle system is mainly composed of the spindle and the broach clamping mechanism. The main shaft is driven to rotate by the motor through a synchronous toothed belt. The broach clamping mechanism mainly tightens and clamps the cutting tool. It is driven by a stepping motor to rotate the worm gear and worm, causing the gear on the worm gear shaft to drive the rack to move up and down. When the rack moves down, it pushes the broach rod to release the cutting tool. When the rack moves up, the broach rod, under the action of the spring force, tightens and locks the cutting tool, completing the loading and unloading of the cutting tool. The movements of the two are interlocked. 3 Analysis and Maintenance of the Causes of Spindle System Faults

(1) The tool changing mechanism is stuck, preventing the tool from being removed from the spindle. The reasons are as follows: There are significant tooth profile errors or tooth side clearances in the worm gear and worm gear mechanism and the sector gear and rack mechanism, which often lead to mechanism jamming faults. When the rack presses down the broach rod, the broach rod cannot move down fully or underfully, and the tool cannot be removed. The positioning reliability of the magnetic sensor for the tool release position is poor, and the rigidity of the screw pressing on the sensor positioning plate is insufficient. Under the conditions of vibration or heat during machine tool processing, positioning errors are prone to occur, resulting in insufficient execution of the tool release control command signal of the stepping motor, insufficient downward movement of the tool pull rod, and inability to remove the tool.

Maintenance method: Correct the tooth profile error and adjust the tooth side clearance to make the worm gear mechanism and the sector gear rack mechanism move flexibly. Replace the sensor positioning plate, increase its rigidity and improve the positioning method to ensure reliable positioning.

(2) The main shaft can operate without tool clamping, but it does not operate after tool clamping is installed.

The reason is that the return spring force of the broaching mechanism is too weak, causing errors in the return Angle of the worm gear/sector gear. The magnetic sensor at the tight tool position does not sense the signal to connect the control relay signal of the spindle motor, and the spindle motor cannot be connected and thus cannot work. The spindle can operate without tool clamping because the return spring of the tool pulling mechanism has no reaction force due to the tool pulling effect. The return spring has sufficient return force to drive the sector gear shaft to rotate and keep the core in the normal position. When the magnetic sensor for locking senses the signal normally, the spindle motor can be connected.

Maintenance method: Increase the preload of the return spring, which is sufficient to drive the sector gear shaft to rotate to a reliable position. Adjust the installation position of the magnetic sensor for the tight knife position to ensure that its signal is sufficient to connect the control relay of the spindle motor, allowing the spindle motor to be powered on and operate. At the same time, modify or increase the control pulse quantity of the stepper motor in the control system, that is, the rotation value of the sector gear shaft.

(3) During normal processing, the spindle often stops working and the processing automatically ends. The main reason is that the rigidity of the positioning plate of the position magnetic sensor is insufficient and the positioning is unreliable. The vibration during machine tool processing causes the installation position of the position magnetic sensor to change, especially the gap between the magnetic sensor and the iron core increases. The position sensing signal of the magnetic sensor is insufficient to drive the control relay of the spindle motor to connect or suddenly disconnects during the processing, thus terminating the processing automatically. In addition, after the machine tool has been running continuously for a long time, the spindle system overheats, the magnetic sensor positioning plate undergoes thermal deformation, and the gap between the magnetic sensor and the core increases (0.1 to 0.3mm), which alters the position sensing signal of the magnetic sensor. This causes the control relay of the spindle motor to suddenly disconnect and terminate during the processing, and the processing automatically ends.

Maintenance method: Replace the sensor positioning plate, increase rigidity and improve the positioning method; Adjust the gap between the magnetic sensor and the core to ensure that the induced signal is sufficient to drive the control relay of the main shaft motor. Atlas air compressor parts