Abstract
This article establishes an axial contact stiffness model of position preloaded ball screw mechanism based on Hertz contact theory. The analysis of dynamic axial contact stiffness is one of the foundations of the research on the dynamic characteristic of the ball screw feed drive system. The model takes into account the coupling relationship between the contact angle and the normal contact force, as well as the coupling relationship between the elastic deformation and the contact deformation coefficient. The static and dynamic axial contact stiffness characteristics of the preloaded ball screw mechanism are studied. The numerical analysis result shows that the static contact stiffness of the preloaded ball screw mechanism increases with the increase in the preload and decreases with the increase in the axial load. The dynamic contact stiffness of the preloaded ball screw mechanism increases with the increase in the screw’s rotational speed. The variation range of dynamic contact stiffness increases with the increase in axial load under the same preload. And the variation range of dynamic contact stiffness decreases with the increase in preload under the same axial load. The axial contact stiffness model established in this article can be used to analyze either static or dynamic contact stiffness of position preloaded ball screw mechanism.
Highlights
Ball screws play a significant role in converting rotary motion into linear motion to carry medium/high loads, which are most frequently used for computer numerical control (CNC) machining equipment.[1]
It is necessary to mention that the axial deformation dFP is a definite value in equation (34). It should be obtained before calculating the variables about contact deformation of a position preloaded ball screw system which is operating at one screw’s rotational speed and under an axial load applied on the left nut
The conclusions are listed below: 1. The changes in static contact stiffness of the preload double-nuts ball screw system are divided into two stages: in the first stage, the static stiffness of the ball screw decreases with the increase in the external axial force; in the second stage, when the axial load is enlarged enough to disengage one of the nuts from the screw, the static stiffness of the ball screw is the same as that of a sing-nut ball screw
Summary
Ball screws play a significant role in converting rotary motion into linear motion to carry medium/high loads, which are most frequently used for computer numerical control (CNC) machining equipment.[1] The most important advantages of the mechanism are its good positional accuracy and high driving speeds. With the growth of demand for high precision, high speed, and high durability in CNC machine tools, high performance and reliability have become the most important indexes for ball screws.[2,3,4]. The preloading method of double-nut ball screw system can mainly be divided into two categories: constant-pressure preload and position preload. Constant-pressure preload is mainly through the addition of springs between two nuts to produce an axial elastic tension force, through which the double-nut ball screw system is preloaded
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