Common failure analysis of machining center spindle

Machining center is a high speed, high precision, high automation, complicated structure, advanced processing equipment in modern manufacturing plays an enormous role, in the event of failure, greatly affect the efficiency of the enterprise, while machining center has a good fault self-diagnosis function, failure occurs most in machining center with alarm message, but sometimes the faults of machining center is integrated form, no alarm information, and is unable to distinguish between mechanical, electrical, or hydraulic pressure problem, CNC system, need maintenance personnel with more knowledge and comprehensive judgment ability and rich experience in maintenance. Based on the production practice, this paper analyzes the common spindle failure in machining center in detail, and puts forward the corresponding maintenance measures, which provides an effective reference for the maintenance of machining center.


1. Common failure analysis of machining center spindle


Machining center spindle usually USES servo speed regulation motor speed regulation, its structure is relatively simple, but the machining center has automatic tool clip, and chip automatic removal device and the spindle quasi-stop device, the common spindle fault also occurs in these parts, under its specific analysis.


1.1 spindle heating and rotation accuracy reduction


The phenomenon of fault: machining out the workpiece hole accuracy is low, cylindrical is very poor, spindle heat quickly, processing noise is very large.


Fault cause analysis: through long-term observation of the spindle of the machine tool, it can be determined that the centering taper hole of the spindle of the machine tool is damaged in the process of multiple tool changes. The main cause of damage is the failure of pulling and inserting the tool in the process of use, which damages the conical surface of the spindle centering hole. After careful analysis, it is found that there are four reasons for the failure of the spindle parts: (1) the main shaft bearing grease, blatantly impurities mixed with dust and moisture, these impurities mainly comes from the processing center with no through distillation and dry compressed air, when the aerodynamic sweep, dust and moisture into the main shaft bearing grease, lead to the main shaft bearing lubrication is not good, produce a large number of jehol noise; (2) there is damage on the locating surface of the conical hole used for locating the cutter in the spindle, which leads to the imperfect match between the conical surface of the spindle and the conical surface of the tool handle, and trace eccentricity appears in the processed hole; (3) the preload of the front bearing of the spindle decreases, resulting in a larger clearance of the bearing; (4) the spring fatigue failure of the automatic clamping device inside the spindle makes the cutter unable to be tightened completely and deviates from the original position.


For the above reasons, fault treatment measures :(1) replace the front-end bearing of the spindle, use qualified grease, and adjust the bearing clearance; (2) grind the positioning surface of the conical hole in the spindle to be qualified, and ensure that the contact surface with the tool handle is not less than 90% by means of coloring test; (3) replace the spring of the clamping device and adjust the pre-tightening force of the bearing. In addition, in the process of operation to often check the spindle hole, knife handle clean and fit, to increase the air filter and drying device, to reasonable arrangement of processing technology, not overload the machine.