Crossed Roller Bearing Hot-Fit Dimensional Control and Preload Adjustment Requirements

During the assembly process of machine tools, crossed roller bearings are commonly used as turntable bearings. However, during assembly, the heating installation method is often adopted. Since the heating temperature and the heating process can easily cause dimensional deviations in the bearings, thereby affecting assembly precision, it is necessary to control the dimensions throughout the process. Here, we have compiled the requirements for hot-fit dimensional control and preload adjustment of crossed roller bearings for your reference.

 Hot-Fit Dimensional Control of Crossed Roller Bearings  

 1. Pre-Assembly Heating  

The outer and inner rings of crossed roller bearings are typically assembled with an interference fit or a clearance fit with minimal clearance. Therefore, during installation, oil bath heating or induction heating methods are generally used to heat the relevant components. The heating temperature should not exceed 80°C. Generally, the bearing housing ring is heated first, and then the bearing outer ring is fitted into the housing bore. Subsequently, the assembled bearing and housing ring are heated together to expand the inner ring dimensions, after which the bearing inner ring is mounted onto the shaft. When using oil bath heating, it is necessary to design and fabricate a heating oil tank, heating electric tubes, temperature control devices, and detection instruments. When using induction heating, the temperature must be carefully controlled, and demagnetization treatment is required after heating.

 2. Dimensional Control During Heating  

Prior to the formal installation of the crossed roller bearing, the dimensional changes of the related components after heating should be actually measured to determine whether the expanded dimensions meet the installation requirements, thereby avoiding installation failure caused by insufficient dimensional expansion during heating. Generally, the assembly control time for the housing ring and bearing heating, as well as the assembly control time for the heated bearing inner ring assembly and shaft fitting, should not exceed 30 minutes, to ensure sufficient dimensional expansion within this period.

Crossed Roller Bearing

Preload Adjustment Requirements for Crossed Roller Bearings  

One of the most critical adjustment tasks during the installation and adjustment of crossed roller bearings is preload control. This is typically achieved by adjusting the thickness of the adjusting shims to control the preload amount, while simultaneously measuring the torque of the rotary table to verify the preload level. When measuring torque, a spring dynamic moment is used to measure the uniform pulling force during rotation, and the actual force arm length is measured to calculate the torque.

During preload of crossed roller bearings, the torque consistency of all bolts must be controlled. The tightening torque should be applied by diagonally tightening the bolts 2 to 3 times. Subsequently, the crossed roller bearings can be installed into the worktable system for trial cutting of the complete machine. The surface roughness of the machined work piece can reflect whether the bearing preload is accurate. If necessary, the bearing preload can be adjusted again until satisfactory roughness and operating performance are achieved.