Modelling of cutting force in hard whirling of ball screws based on uncut chip geometry

Abstract

Hard whirling is a highly efficient and green process for precision ball screw machining. Due to the intermittent cutting characteristics and the helical motion of the tool, the cutting forces are periodic and time-varying, making it extremely challenging to establish an accurate cutting force model. This paper proposes a cutting force modelling method based on the transient geometric characteristics of uncut chips, subject to the essential link between uncut chips and cutting forces. The time-varying features of the chip are revealed by building an accurate 3D digital model of the uncut chip. An equivalent cutting simulation model is developed using the discrete cross-section of the chip, and the effect of cutting parameters and tool edge on the cutting forces are investigated. A combination of simulation and experiment is presented to identify cutting force model coefficients, and the theoretical cutting force model for ball screw hard whirling is established. The results show that the uncut chip cross-sectional area and edge length involved in cutting first increase and then decrease, and the equivalent numerical simulation method based on the transient geometry of uncut chips can obtain more accurate cutting forces. The combined simulation and experimental strategy achieve fast and low-cost identification of cutting force coefficients, and the established cutting force model has good prediction accuracy. This study supports the investigation of the cutting mechanism of hard whirling, the optimisation of process parameters and the improvement of machining quality.

Keywords

• hard whirling
• cutting force model
• uncut chip
• tool edge
• coefficient identification