Ball screw failure is a variety of, there is no fixed mode.Some faults are gradual fault, there should be a development process, with the increase in the use of time more and more serious;Sometimes it is sudden happening fault, do not have apparent omen commonly, and happen suddenly, this kind of fault is all sorts of adverse factor and outside action and produce jointly.Therefore, the correct detection to determine the real cause of failure, is the premise of rapid and accurate maintenance.
1) detection and repair of clearance between ball screw nut pair and support system
When the numerical control machine tool appears the reverse error is large, the positioning accuracy is not stable, the quadrant appears the knife mark, first of all, to detect whether the screw system clearance.Detection methods are: with the dial gauge with the ball on one end of the screw in the center hole, measuring the screw axial channeling, another dial gauge measuring table movement.Turn the lead screw forward and backward, observe the values reflected on the two dial gauges, and confirm the fault location according to the different changes of the values.
A) detection and repair of clearance of leadscrew support bearing
If the dial indicator for measuring the lead screw does not oscillate when the lead screw rotates in the positive and negative direction, it indicates that the lead screw does not move.If the dial indicator pointer swings, the lead screw has channeling phenomenon.The difference between the maximum and minimum measured values of the dial gauge is the axial displacement distance of the screw.At this point, we need to check whether the back cap of the support bearing is locked, whether the support bearing has worn out, whether the preloaded bearing washer is appropriate.If there is no problem with the bearing, just reinstall the preloaded washer.If the bearing is damaged, replace the bearing with a preloaded washer and tighten the back cap.The axial movement of the screw mainly depends on the precision of the preloading washer of the supporting bearing.The most ideal state of screw mounting precision is that there is no positive and negative clearance, and the supporting bearing should have an interference of about 0.02mm.
B) detection and maintenance of clearance generated by double nut pairs of ball screw
Through detection, if it is confirmed that the fault is not caused by the lead screw movement.That is to consider whether there is a gap between the screw nut pair, the detection method in this case is basically the same as the detection of screw movement.Use dial meter to measure the working table connected with the nut, turn the screw forward and backward, detect the maximum clearance between the screw and the nut, and then adjust.
Adjust the thickness of gasket 4, so that the left and right nuts 1, 2 produce axial displacement, so as to eliminate the ball screw nut pair clearance and produce pre-tightening force.Because the screw nut pair structure is different, so the adjustment method is also different.
C) inspection and maintenance of single nut pair
For single nut ball screw, clearance between screw nut pairs cannot be adjusted.If the screw nut pair is detected to have clearance.Firstly, check whether the thread arc of the screw and nut has been worn out. If the wear is serious, the full set of screw nut must be replaced.
If the inspection wear is minor, you can replace a larger diameter ball to repair.Firstly, the maximum clearance of screw nut pair was detected, which was converted into the increase of ball diameter, and then the appropriate ball was selected for re-assembly.Such maintenance is relatively complex, takes a long time and requires a high level of technology.
D) the gap between the nut flange and the workbench is not fixed properly
This problem is easy to be ignored generally, because the machine tool reciprocating movement for a long time, the screw that fixes farrah dish loosens to produce clearance, when checking clearance of screw nut of screw screw the highest when this fault element is removed first, lest go astray when repairing.
E) maintenance of faults such as unstable movement of ball screw nut pair and excessive noise.
Ball screw nut pair movement is not smooth and noise is too large, mostly due to poor lubrication, but sometimes may be due to servo motor drive parameters are not adjusted.
2) poor lubrication of bearing and screw nut pair
Machine tools in the work such as noise and vibration, in the detection of mechanical transmission part no problem, the first to consider the problem of poor lubrication, many machine tools after many years of operation, the screw nut automatic lubrication system is often blocked, not automatic lubrication.High temperature and high speed grease can be added to the bearing and nut to solve the problem.Grease can guarantee the normal operation of bearings and nuts for several years.
Post time: Nov-27-2018