With the rapid development of numerical control technology, “compound, high-speed, intelligent, precision, environmental protection” has become the main trend of the development of machine tool industry technology.  Similarly, the precision bearings assembled in the spindle and feed part of the high precision CNC machining center must meet the requirements of high precision, high speed, low noise, trouble-free and high reliability of the machine tool..

Spindle, lead screw with precision bearings as the machine tool’s basic accessories, its performance directly affects the machine tool’s speed, rotary accuracy, rigidity, anti-vibration cutting performance, noise, temperature rise and thermal deformation, and then affect the machining parts precision, surface quality, etc..

The assembly quality of precision bearings directly affects its working state and service life. Many failures of CNC machining centers are caused by improper assembly of bearings. Therefore, sufficient attention should be paid to the assembly technology of precision bearings.  Now the assembly points of high-speed precision bearings are summarized as follows:

a.When the interference is large, heating box, oil bath heating or inductor heating bearing can be used to install, heating temperature range of 80℃ ~ 100℃, the highest can not exceed 120℃.  At the same time, the application of nuts or other appropriate methods to tighten the bearing, in order to prevent the bearing cooling after the width direction of contraction and the gap between the ring and the shaft shoulder.

b.When the bearing is installed, equal pressure must be applied on the circumference of the end face of the ring, and the ring is pressed into it. It is not allowed to knock the end face of the bearing directly with the tools ð¨±?  In the case of small interference, the end face of the bearing ring can be pressed by the sleeve at normal temperature, and the center of the assembly sleeve can be tapped with the ð¨±? head to balance the ring through the sleeve  Assembly force must not be transmitted through the rolling body, to avoid direct hammering bearing rings.  When pressing in, it should be ensured that the outer ring end face and shell shoulder end face, the inner ring end face and shaft shoulder end face are pressed tightly, no clearance is allowed.

c.Mechanical press or hydraulic press must use assembly sleeve pressure, and ensure that it is in a horizontal state, such as tilt will lead to bearing groove damage due to force, so that the bearing produces abnormal sound.  The assembly sleeve should completely contact the whole circumference of the bearing inner ring or outer ring end face

Designers should consider disassembly in the installation position of precision bearings. Interference fit is generally used for installation of precision bearings, so disassembly grooving should be set on the shaft or bearing seat hole during design to facilitate disassembly of bearings.

If the removed precision bearings need to be reused, the disassembly treatment should be more careful operation.  When removing precision bearings, the following points should be paid attention to: Avoid hitting bearing rings directly;  The disassembly force should not be transmitted through the bearing rolling body, the disassembly force should be transmitted through the bearing inner ring when the precision bearing is removed from the shaft, and the disassembly force should be transmitted through the bearing jacket when the precision bearing is removed from the bearing seat hole;  Once the precision bearing is disassembled, it should be cleaned, dried and coated with anti-rust oil or grease to avoid corrosion of the bearing.

If the above points are paid attention to in the assembly and disassembly process of precision bearings, the control of temperature rise of the spindle, the high precision and high speed trouble-free operation of the spindle and the control of transmission accuracy will have a more ideal effect.

e-mail:bearing6@hyzcgroup.com