Thermal Analysis of a Ball-Screw System

Abstract

High speed ball-screw system has serious friction heat to form thermal expansion to each component. An analyzing model considering with contact deformation and thermal expansion is established in realizing positioning error for a high speed ball-screw system. A finite element model of nut is also built in calculating elongation of nut. Surface strain of nut is measured by strain gages in order to confirm with data obtained from finite element model. Temperature of nut and screw were also measured by thermal couples and are used in calculation of elongation by the use of linear elongation equation. The tendency of positioning error is well estimated by the analyzing model. The model can be used in feedback positioning control factor and develop precision high speed ball-screw system.

Surface temperature and wear particle analysis of vertical motion double-nut ball screws

“…It reveals that the temperature distribution and thermal deformation of a ball-screw shaft can be considered to vary only in the axial direction. An experiment measured by thermocouples and estimated by an 1D elongation equation and contact mechanism (Wei et al , 2012a, 2012b) shows good agreement between analysis and experiment. The estimated model proposed by Wei et al is more accurate than a single linear expansion equation in calculating the thermal expansion of the nut.…”

“…As the above analysis shows, input energy, Q in , comes from frictional energy. The friction coefficient is 0.05 calculated from a previous work (Wei et al , 2012a, 2012b). Figure 7 shows the experimental and simulated values of the transient temperature during a test procedure at the different test times.…”

“…The contact load includes an initial preload load of 45 kgf and the axial load. This caused contact stresses between the ball and screw from 0.8 to 1.2 GPa, calculated from kinematical analysis during testing (Wei et al 2012a, 2012b). These are the general operating conditions of commercial tapping machine.…”

“…Therefore, wear monitoring is a way to index performance of the ball screw. A sliding wear analysis combining the three-body micro-contact model (Horng et al , 2006) with kinematical analysis of the ball screw was established by Wei et al (2012a, 2012b), to examine the effect of wear depth on preload variation at the different rotational speeds and elliptic ratios. The wear depth and preload are reduced with an increasing elliptic ratio of surface roughness because the increase in the elliptic ratio can reduce the plastic contact ratio of asperity.…”