1、 Spindle component malfunction
The spindle is a major core component of large CNC machining centers, and the surface accuracy of machining is largely related to the spindle, so the quality of the spindle is crucial. Due to the use of speed regulating motors, the spindle box structure of CNC machine tools is relatively simple, and the parts that are prone to failure are the automatic tool clamping mechanism and automatic speed regulating device inside the spindle. To ensure that the tool holder does not loosen on its own during work or power outages, the automatic tool clamping mechanism uses spring clamping. If the tool cannot be loosened after clamping, consider adjusting the pressure and stroke switch device of the loosening hydraulic cylinder or adjusting the nut on the disc spring to reduce the amount of spring compression. In addition, the problems of spindle heating and spindle box noise cannot be ignored. At this time, the main considerations are to clean the spindle box, adjust the amount of lubricating oil, ensure the cleanliness of the spindle box, replace the spindle bearings, repair or replace the spindle box gears, etc.
2、 Feed transmission chain malfunction
In the feed transmission system of large CNC machining centers, ball screw pairs, static pressure screw nut pairs, rolling guides, static pressure guides, and plastic guides are commonly used. So there is a malfunction in the feed transmission chain, mainly reflected in the decrease of motion quality. For example, mechanical components do not move to the specified position, operation is interrupted, positioning accuracy decreases, reverse clearance increases, crawling, and bearing noise increases (after collision).
For such faults, the following measures can be taken to prevent them:
(1) Improving transmission accuracy by adjusting the pre tension of each motion pair, adjusting loose links, eliminating transmission clearances, shortening the transmission chain, and setting reduction gears in the transmission chain can also improve transmission accuracy.
(2) Improve transmission stiffness. Adjusting the pre tightening force of the screw nut pair and supporting components, as well as selecting the appropriate size of the screw itself, are effective measures to improve the transmission stiffness. Insufficient stiffness can also cause crawling and vibration of the workbench or trailer, as well as create reverse dead zones, affecting transmission accuracy.
(3) Improve motion accuracy. On the premise of meeting the strength and stiffness of components, minimize the mass of moving parts, reduce the diameter and mass of rotating parts, in order to reduce the inertia of moving parts and improve motion accuracy.
(4) The rolling guide rail is sensitive to dirt and must have good protective devices. In addition, the pre tensioning force of the rolling guide rail should be selected appropriately, as excessive force can significantly increase the traction force. The static pressure guide rail should have a set of oil supply system with good filtering effect.
