Motorized Linear Stages are ready for delivery to Singapore

Motorized Linear Stages( linear motor stage,motorized linear translation stage,precision motorized linear stages)are ready for delivery to Singapore. 

Installation form of motor base + ball screw and screw rod, that is, Motorized Linear Stages

As the feed transmission chain of CNC machine tool, the assembly form and accuracy of ball screw pair determine the positioning accuracy of CNC machine tool, and also affect the stability of interpolation operation of feed shaft.

A、 Installation form and stress of ball screw pair(linear motor stage)

The common lead screw support of the feed shaft of the machine tool is in the following forms:

1. Fixed at one end – free at one end
   One end of the lead screw is fixed and the other end is free. The fixed end bearing bears both axial and radial forces. This support method is used for short lead screws with small stroke or machine tools with full closed loop, because the mechanical positioning accuracy of this structure is the most unreliable, especially for lead screws with large length diameter ratio (ball screws are relatively slender), the thermal denaturation is obvious, and it is normal for 1.5m long lead screws to change 0.05~0.10mm in cold and hot environments. However, due to its simple structure and convenient installation and debugging, many high-precision machine tools still use this structure, but it must be equipped with grating and adopt full closed-loop feedback.
2. Fixed at one end – supported at the other end
   One end of the lead screw is fixed and the other end is supported. The fixed end bears both axial force and radial force; The supporting end only bears radial force, and can make a small amount of axial floating, which can reduce or avoid the bending caused by the dead weight of the lead screw, and at the same time, the thermal deformation of the lead screw can extend freely to one end. This structure is the most widely used. At present, this structure is used in small and medium-sized CNC lathes and vertical machining centers in China.
3. Fixed at both ends
   Both ends of the lead screw are fixed. The fixed end bearing can bear the axial force at the same time. This support method can apply appropriate preload to the lead screw, improve the support stiffness of the lead screw, and partially compensate for the thermal deformation of the lead screw.
   This scheme is often used for large machine tools, heavy machine tools and high-precision boring and milling machines. However, the adjustment of this lead screw is cumbersome. If the preload at both ends is too large, the final stroke of the lead screw will be longer than the design stroke, and the pitch will also be larger than the design pitch. If the pre tightening force of the lock nuts at both ends is not enough, it will lead to the opposite result, and it is easy to cause vibration of the machine tool and reduce the accuracy. Therefore, such lead screws must be adjusted according to the original manufacturer’s instructions or with the help of instruments (dual frequency laser measuring instrument).

B、 Arrangement and nomenclature of ball screw bearings

First of all, we understand the typical feed shaft transmission chain. The final support of the ball screw(motorized linear translation stage) is the near end support bearing and the far end support bearing. These two groups of bearings push the axial force through mutual action, that is, the screw shaft skillfully uses the “angular contact bearing” which can withstand both radial and axial forces.
When the inner retaining ring and the outer retaining ring of the bearing are subjected to a group of forces in the opposite direction, the bearing steel balls bear a pair of opposite forces. From the perspective of statics, when the object is stationary, this pair of forces are equal in size and opposite in direction.
As the machine tool lead screw transmission, the axial force from the workbench acts on the inner ring of the bearing. If we restrict the lead screw from moving, as long as a force with opposite direction and equal size is applied on the outer ring of the bearing, so the axial force is balanced. In addition, due to the rolling friction between the inner and outer rings, the flexible rotation of the lead screw is ensured.
For the screw drive of CNC machine tools, it is necessary to control the bearing clearance (the clearance between the steel ball and the inner and outer rings) according to different conditions. For the transmission of low-speed and high torque, this clearance is required to be interference, that is, to make the steel ball squeeze and deform when rolling in. From the perspective of coordination, the clearance is negative. For the load with a smaller high speed, it is necessary to have a larger clearance and reserve the thermal expansion coefficient of the steel ball and inner ring(precision motorized linear stages) after high speed operation.
The constraint of the lead screw is completed by the axial and radial constraints of the near end bearing and the far end bearing. The force condition of the lead screw(precision motorized linear stages) under different installation forms and the installation form of the ball lead screw bearing are helpful for the daily maintenance in the future, especially the accuracy adjustment of the transmission chain.

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