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CNC Gantry Type Machine Center-lead Screw Vibration

Dec 19, 2019

cnc gantry type machine center

CNC gantry type machine center, during the assembly and debugging process, the vibration generated by the rotating movement of the machine is inevitable. The vibration generated by the machine will cause certain harm to the normal use of the machine tool, it will reduce the working performance of the machine tool, even at all. Inability to work will also cause accelerated wear and fatigue of some parts, reducing the service life of the machine. When some abnormal vibration occurs, measures must be taken to eliminate it to ensure the safe operation of the machine tool. During the assembly and commissioning of CNC gantry type machine center, the vibration of the lead screw is often encountered. In addition to the factors such as the system electrical parameter setting and improper selection, there are also mechanical reasons, mainly including the following: several aspects:


One, Screw installation factors


Now the CNC gantry type machine center including CNC machine tools is a ball screw, and the transmission precision is high, meanwhile, it also has higher requirements for the accuracy of our assembly and installation. The screw transmission structure is mainly composed of the screw itself, the screw nut, the screw seat (also called the bearing seat), the screw bearing, the lock nut, the coupling, the servo motor and so on. During the installation process, it is necessary to ensure that the axis of the screw shaft is parallel to the reference plane of the movement guide rail. If the installation error is large, the carriage will bend and deform the screw during the movement, and the screw will be subject to uneven rotation force, which will cause Vibration phenomenon.


Second, the connection and installation factors of the screw nut and the carriage


CNC gantry type machine center During the installation of the screw nut and the carriage, sometimes due to the processing of the end surface of the carriage, the screw hole on the screw nut and the installation hole on the joint surface of the carriage interfere with each other, or the installation surface and The reference (rail) surface is not vertical, that is, the mounting surface is not parallel to the screw nut joint surface, resulting in the screw nut tightening screw to force the screw to deform and vibrate.


Third, the installation factors of the coupling


The CNC gantry type machine center motor drives the screw to rotate through an elastic coupling. In this part of the installation process, it must first ensure that the radial runout error of the screw end meets the design requirements, and secondly, ensure that the motor mounting surface and the The axis of the screw shaft is vertical, and the axis of the rotation axis of the motor coincides with the axis of the screw shaft, which is generally guaranteed by the positioning holes required by the design. After zui, use a torque wrench to evenly tighten the fastening screws of the expansion sleeve gland on the coupling. If the three conditions are not met, the screw and the coupling will vibrate.


Fourth, the factor of the axial clearance of the screw


During the movement of the CNC gantry type machine center, if the axial clearance of the lead screw is too large, vibration will also occur, including the crawling of the pallet. This is because the numerical control axis itself has a scale. When the scale is in effect, according to the feedback of the grating signal, the servo motor will continuously rotate forward and backward to correct the position of the carriage.


Five, Installation factors of the grating reading head (moving ruler) bracket


The installation of the CNC gantry type machine center grating reading head bracket is very important during the installation of a machine tool with a scale. If the grating bracket is not installed properly, the data read by the grating reading head will be incorrect, causing the feedback signal to be unstable. , Cause the motor to work abnormally and generate vibration, and make the positioning accuracy of the machine tool unstable


Sixth, bearing quality factors


During the movement of the machine tool, the CNC gantry type machine center sometimes causes bearing quality problems; the bearing raceway fails or the retaining ring is damaged, causing the screw to vibrate. In this case, it can be judged according to the vibration sound source of the screw. When the bearing has a problem, the screw will emit a vibration sound during the movement. During the movement of the carriage, for example, the closer the carriage is to the support seat at one end of the screw , The higher the screw vibration audio, the bearing at this end may have problems.


Seven, other factors


During the use of CNC gantry type machine center, lead screw vibration may also be caused by inadequate lubrication, sliding guide wear and failure, and motor encoder failure, etc. In this case, check each item one by one to eliminate vibration problems.


In summary, if the CNC machine tool has a screw vibration phenomenon, it must take measures in time to address the various fault conditions appearing in various assembly processes, using the various methods and means analyzed above, to actively eliminate the fault, so as to Ensure the assembly quality of the machine tool, reduce the repair rate of the machine tool, and extend the service life of the machine tool.

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