A Model for Predicting Dynamic Cutting Forces in Sand Mould Milling with Orthogonal Cutting

Zhong-De Shan,Fu-Xian Zhu

doi:10.1186/s10033-018-0306-6

Zhong-De Shan, Fu-Xian Zhu

Open Access

https://doi.org/10.1186/s10033-018-0306-6

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Abstract

Cutting force is one of the research hotspots in direct sand mould milling because the cutting force directly affects the machining quality and tool wear. Unlike metals, sand mould is a heterogeneous discrete deposition material. There is still a lack of theoretical research on the cutting force. In order to realize the prediction and control of the cutting force in the sand mould milling process, an analytical model of cutting force is proposed based on the unequal division shear zone model of orthogonal cutting. The deformation velocity relations of the chip within the orthogonal cutting shear zone are analyzed first. According to the flow behavior of granular, the unequal division shear zone model of sand mould is presented, in which the governing equations of shear strain rate, strain and velocity are established. The constitutive relationship of quasi-solid–liquid transition is introduced to build the 2D constitutive equation and deduce the cutting stress in the mould shear zone. According to the cutting geometric relations of up milling with straight cutting edge and the transformation relationship between cutting stress and cutting force, the dynamic cutting forces are predicted for different milling conditions. Compared with the experimental results, the predicted results show good agreement, indicating that the predictive model of cutting force in milling sand mould is validated. Therefore, the proposed model can provide the theoretical guidance for cutting force control in high efficiency milling sand mould.

Highlights

1 Introduction Sand mould milling is the process of milling casting mould directly with CNC milling technology, in which the mould production does not use molds or patterns
In order to improve the integrity and accuracy of sand mould structure and reduce the tool wear by controlling the size of cutting force, in this paper, the quasi-solid–liquid transition theory of granular system is introduced into the parallel-sided shear zone model of the cutting process to analyze the flow stress of shear zone
4.2 Sand Mould Milling Process Analysis From the predicted and measured milling forces amplitudes shown in Figure 10, the main machining parameters that significantly influence the cutting force are the following: 4.1.2 Effect of Shear Zone Thickness During milling, the thickness of cutting layer varies with the rotation of cutter (Eq (24)), and the thickness of the shear zone is changed

Summary

Introduction

Sand mould milling is the process of milling casting mould directly with CNC milling technology, in which the mould production does not use molds or patterns. An accurate prediction of the dynamic cutting forces of milling sand mould is very important to study. Merchant [9] proposed the single shear area model based on the flow rules of metal material in cutting. The quasi-solid–liquid transition feature of granular materials can be considered as an appropriate basis for further studying the deformation of shear area when cutting sand mould. In order to improve the integrity and accuracy of sand mould structure and reduce the tool wear by controlling the size of cutting force, in this paper, the quasi-solid–liquid transition theory of granular system is introduced into the parallel-sided shear zone model of the cutting process to analyze the flow stress of shear zone. Through studying the shear strain rate of shear zone, the model of dynamic cutting forces in sand mould milling is established. The cutting force of milling with straight cutting edges is predicted and discussed

Theoretical Analysis and Modeling

Results and Discussions

Conclusions