Precision slewing bearing clearance selection and actual application

In order to let the precision slewing bearing to rotate smoothly to obtain an ideal runout value when in use, the clearance value will generally be small, zero or negative when designed and manufactured, the corresponding clearance value is generally 0 to 0.05. ≤0, -0.05 to -0.01, the corresponding preload is: no preload, light preload, heavy preload.

When processing, we can measure the raceway size according to the method of measuring the raceway size. According to the measurement data, calculate the clearance value (whether it is a positive clearance or a negative clearance), check the calculated clearance value after the processing is completed. Use a dial indicator to directly measure the clearance, for negative clearance, use a dynamometer to measure the slewing ring starting torque. According to the starting torque to judge the slewing bearing interference. The starting torque is also a value that must be known in the slewing bearing use, which determines the slewing bearing reducer and motor selection.

To measure the slewing bearing starting torque, the slewing bearing starting force must be measured first and a dynamometer is needed. Because the max starting force appears at the moment when the slewing bearing is about to rotate, so you need a dynamometer that can record the maximum value of the measurement, measure the driving force of the slewing bearing.

Starting torque = starting force * moment arm, starting force can be measured by dynamometer, we generally install a bolt on slewing bearing outer ring hole, use a dynamometer to measure the starting force of the slewing bearing at the bolt, the radius of the outer ring bolt hole distribution circle is the moment arm, the starting torque of slewing bearing is calculated by starting force and moment arm. For the same slewing ring, the difference in starting torque can reflect the size of the negative clearance slewing bearing clearance value, the starting moment is larger and the clearance value is smaller, then the preload is greater.

The clearance value selection should also consider the customer’s equipment situation. The slewing ring clearance values are smaller, the requirements for installation and use are higher. The flatness error of the installation foundation and the unbalance load in the use of the slewing bearing will cause the slewing bearing to be slightly deformed.

The slight deformation of the slewing bearing can be offset by the clearance when the clearance is large and the slewing bearing can rotate normally after installation. But if it is a small or negative clearance, the slewing bearing has no extra clearance to resist small deformations. If the slewing bearing is deformed, it will get stuck, rotate badly or even get stuck, causing damage or unusable.

Therefore, the selection of small clearance for precision slewing rings requires comprehensive slewing accuracy, machining accuracy of the equipment installation foundation, comprehensive analysis and evaluation of the user’s specific use conditions, then selecting the appropriate clearance value to ensure accuracy and ensure that it can be installed and used on site.