Hebei Yintai guide rail, SMR65LS original guide rail, large inventory in Anang Mall

Hebei Yintai guide rail, SMR65LS original guide rail, large inventory in Anang Mall

PMI linear guide railInstallation method:

PMI linear guide railAs the feed transmission chain of CNC machine tools, its assembly form and accuracy determine the positioning accuracy of the CNC machine tool, and also affect the smoothness of the feed axis interpolation operation.
1、 Installation form and force of PMI linear guide rail
The common forms of guide rail support for the feed axis of control machine tools are as follows:
1. One end fixed - one end free
One end of the guide rail is fixed, and the other end is free. Fixed end bearings simultaneously bear axial and radial forces. This support method is used for short guide rails with small stroke or for fully closed-loop machine tools, because the mechanical positioning accuracy of this structure is the least reliable, especially for guide rails with a large aspect ratio (linear guide rails are relatively slender), and thermal deformation is very obvious. It is normal for a 1.5m long guide rail to change by 0.05-0.10mm in different cold and hot environments. However, due to its simple structure and easy installation and debugging, many high-precision machine tools still use this structure, but it is necessary to install gratings and adopt fully closed-loop feedback.
2. Fixed at one end - supported at the other end
PMI linear guide rail is fixed at one end and supported at the other end. The fixed end simultaneously bears axial and radial forces; The supporting end only bears radial force and can undergo slight axial floating, which can reduce or avoid bending caused by the self weight of the guide rail. At the same time, the thermal deformation of the guide rail can be freely extended towards one end. This structure is the most widely used, currently used in small and medium-sized CNC lathes, vertical machining centers, and other applications in China.
3. Fixed at both ends
Both ends of the PMI guide rail are fixed. Fixed end bearings can simultaneously withstand axial forces. This support method can apply appropriate pre tension to the upper silver guide rail, improve the support stiffness of the guide rail, and partially compensate for the thermal deformation of the guide rail.
This scheme is commonly used for large machine tools, heavy-duty machine tools, and high-precision boring and milling machines. However, the adjustment of this type of guide rail is relatively complicated. If the pre tension force at both ends is too large, it will result in the final stroke of the guide rail being longer than the design stroke and the pitch being larger than the design pitch. If the pre tightening force of the locking nut at both ends is insufficient, it will lead to opposite results and easily cause machine tool vibration, resulting in reduced accuracy. So, when disassembling and assembling such guide rails, it is necessary to adjust them according to the original manufacturer's instructions or with the help of an instrument (dual frequency laser measuring instrument).
2、 Arrangement and naming of PMI linear guide bearings
Firstly, we understand the typical feed shaft transmission chain, and ultimately the proximal and distal support bearings support the linear guide rail. These two sets of bearings interact with each other to resist axial forces, which cleverly utilizes the bi-directional force characteristics of "angular contact bearings" that can withstand both radial and axial forces on the guide rail shaft.
When the inner and outer retaining rings of the bearing are subjected to a set of opposite forces, the bearing steel balls bear a pair of opposing forces. From a static perspective, when the object is stationary, this pair of forces is equal in magnitude and opposite in direction.
As a machine tool guide rail transmission, the axial force from the worktable acts on the inner ring of the bearing. If we constrain the guide rail not to move, we only need to apply a force of opposite direction and equal magnitude on the outer ring of the bearing, so that the axial force is balanced. Due to the rolling friction between the inner and outer rings, the flexible rotation of the guide rail is ensured.
For CNC machine tool guide rail transmission, it is necessary to control the clearance of the bearings (the clearance between the steel ball and the inner and outer rings) according to different situations. For low-speed and high torque transmission, this clearance needs to be interference fit, which means that the steel ball needs to be squeezed and deformed when rolling inside. From the perspective of fitting, the clearance is negative. For smaller loads at high speeds, a larger clearance is required to reserve the thermal expansion coefficient of the steel ball and inner ring after high-speed operation.
The constraint of PMI linear guide rail is achieved through the axial and radial constraints of the proximal and distal bearings. The force situation of the guide rail under different installation forms and the installation form of the linear guide rail bearings are helpful for future daily maintenance, especially for adjusting the accuracy of the transmission chain.