Inspection and maintenance of screw rod
There are many kinds of faults caused by ball screw, and there is no fixed law. Some failures are progressive failures and require a development process. As the use time increases, they become more and more serious; Sometimes it is a sudden failure, usually without obvious signs, but it occurs suddenly. This kind of failure is multifaceted and is caused by the interaction of unfavorable factors and the outside world. Therefore, determining the cause of the failure through correct detection is the premise of rapid and accurate maintenance.
1)Inspection and repair of clearance between ball screw nut pair and support system
When the CNC machine tool has a large reverse error, the positioning accuracy is unstable, or the tool passes the quadrant, first check whether the screw system has a gap. The detection method is: use a dial gauge to match a steel ball in the center hole at one end of the lead screw to measure the axial movement of the lead screw, and use another dial gauge to measure the movement of the worktable. Rotate the screw forward and reverse, observe the values reflected on the two dial indicators, and determine the fault location according to the change of the values.
a)Inspection and repair of bearing clearance of screw support
For example, the pointer of the dial gauge measuring the screw rod does not swing when the screw rod rotates forward and backward, indicating that the screw rod does not move. If the pointer of the dial indicator swings, it means that the lead screw is moving. The difference between the larger and smaller measurements of the dial gauge is the axial movement distance of the lead screw. At this time, it is necessary to check whether the rear cover of the support bearing is locked, whether the support bearing is worn, and whether the pre-tightened bearing washer is appropriate. If there is no problem with the bearing, just reinstall it with pre-installed washers. If the bearing is damaged, you need to replace the bearing, reinstall the pre-tightened washer, and then tighten the back cover. The size of the axial movement of the lead screw mainly depends on the accuracy of the pre-loaded washer of the support bearing. The ideal state of screw rod installation accuracy is that there is no positive or negative clearance, and the support bearing should have0.02mmThe amount of interference on the left and right.
b)Inspection and maintenance of clearance generated by ball screw double nut pair
Through the test, if it is confirmed that the fault is not caused by the screw movement. Need to consider whether there is a gap between the screw and the nut pair. In this case, the detection method is basically the same as the detection of the screw movement. Use a dial gauge to measure on the workbench connected to the nut, rotate the screw in the positive and negative directions, detect the large gap between the screw and the nut, and then adjust it.
The method is to adjust the washer4the thickness of the left and right nuts1,2The axial displacement is generated, so as to eliminate the clearance of the ball screw nut pair and generate the preload. Because the structure of the screw nut pair is different, the adjustment method is also different, here is not listed one by one.
c)Inspection and Maintenance of Single Nut
For single nut ball screws, the gap between the screw nut pairs cannot be adjusted. If it is detected that there is a gap in the screw nut pair. First, check whether the thread arc of the screw rod and nut has worn out. If the wear is severe, the complete set of nuts must be replaced.
If there is slight wear in the inspection, a larger diameter ball can be replaced for repair. First detect the large gap of the screw nut pair, convert to the increase of the ball diameter, and then select the appropriate ball to reassemble. Such maintenance is more complicated, takes a long time and requires high technical requirements.
Screw rod
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2024-01-02
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