How to detect and repair common faults of ball screw

The failures caused by ball screw are various and have no fixed mode. Some faults are gradual faults, which need a development process and become more and more serious with the increase of service time; Sometimes it is a sudden failure, usually without obvious symptoms, but it occurs suddenly. This kind of failure is caused by various adverse factors and the joint action of the outside world. Therefore, it is the premise of fast and accurate maintenance to determine the real fault cause through correct detection.

1. Inspection and repair of clearance between ball screw nut pair and support system
When the CNC machine tool has large reverse error, unstable positioning accuracy, and tool marks across the quadrant, first check whether the lead screw system has clearance. The detection methods are as follows: put a dial indicator with a steel ball in the center hole at one end of the lead screw, measure the axial movement of the lead screw, and measure the movement of the workbench with another dial indicator. Turn the lead screw forward and backward, observe the values reflected on the two dial indicators, and confirm the fault position according to the different changes of the values.

2. Inspection and repair of the clearance of the support bearing of the lead screw
If the pointer of the dial indicator for measuring the lead screw does not swing when the lead screw rotates in the positive and negative directions, it means that the lead screw does not move. If the pointer of the dial indicator swings, it indicates that the lead screw moves. The difference between the maximum and minimum measured values of the dial indicator is the axial displacement distance of the lead screw. At this time, we need to check whether the back cap of the support bearing is locked, whether the support bearing has worn out, and whether the preloaded bearing washer is suitable. If there is no problem with the bearing, just refit the preloaded washer. If the bearing is damaged, it is necessary to replace the bearing, refit the preloaded washer and tighten the back cap. The axial movement of the lead screw mainly depends on the accuracy of the preloaded washer of the support bearing. The most ideal condition for the installation accuracy of the lead screw is that there is no positive and negative clearance, and the support bearing also has an interference of about 0.02mm.

3. Detection and maintenance of clearance produced by ball screw and double nut pair
Through detection, if it is confirmed that the fault is not caused by the movement of the lead screw. It is necessary to consider whether there is a gap between the screw and nut pairs. The detection method for this situation is basically the same as that for detecting the movement of the screw. Use a dial indicator to measure the maximum clearance between the lead screw and the nut on the workbench connected to the nut, and then adjust it.

4. Inspection and maintenance of single nut pair
For single-nut ball screw, the clearance between the screw and nut pair cannot be adjusted. If it is detected that there is clearance in the screw nut pair. First, check whether the thread arc of the lead screw and nut has been worn. If the wear is serious, replace the full set of lead screw nuts.

If the wear is slight, the ball with larger diameter can be replaced to repair. First, detect the maximum clearance of the screw nut pair, convert it into the increase of the ball diameter, and then select the appropriate ball for reassembly. Such maintenance is relatively complex, takes a long time, and requires high technical level.

5. The gap caused by the connection between nut flange and workbench is not fixed
This problem is often overlooked. Because of the long-term reciprocating movement of the machine tool, the screws that fix the faraday plate are loose and produce a gap. When checking the clearance of the lead screw nut, the fault factor should be eliminated first to avoid detours during repair.

6. Maintenance of ball screw nut pair with unstable movement and excessive noise
The uneven movement and excessive noise of the ball screw nut pair are mostly caused by poor lubrication, but sometimes the servo motor drive parameters are not adjusted properly.

7. Poor lubrication of bearing and screw nut pair
If the machine tool produces noise and vibration during operation, the problem of poor lubrication should be considered first after detecting that there is no problem with the mechanical transmission part. After many years of operation of the machine tool, the automatic lubrication system of the lead screw nut is often blocked and cannot be automatically lubricated. The problem can be solved by adding high-temperature and high-speed resistant grease into bearings and nuts. The lubricating grease can ensure the normal operation of bearings and nuts for several years.

8. Servo motor drive problem
Some machine tools produce vibration and creep during movement, and the mechanical parts are often inspected without problems. No matter how adjusted, vibration and creep can not be eliminated. After careful inspection, it is found that the servo motor drive gain parameter is not suitable for the actual operation condition. After adjusting the gain parameters, vibration and creep can be eliminated.

Ball screw is an ideal product for converting rotary motion into linear motion, or linear motion into rotary motion. Select the ball screw to identify Tihao machinery and ensure its quality. The ball screw is the most commonly used transmission element in tool machinery and precision machinery. Its main function is to convert the rotary motion into linear motion, or torque into axial repeated force. At the same time, it has the characteristics of high accuracy, reversibility and high efficiency. Because of its small friction resistance, ball screw is widely used in various industrial equipment and precision instruments!

Source: Tihao Machinery