Increasing lathe machining stability by using a composite steel–polymer concrete frame

Abstract The paper presents the process of designing a lightweight vertical lathe with a steel–polymer frame. The purpose of using such a frame was to increase the stability of machining. As part of the study presented in this paper, polymer concrete was developed to provide a significant increase in the damping of steel structures (increase in the modal damping ratio for a steel beam by 239% and 81% reduction in the amplitude of the receptance function for the dominant resonance). Finite element models of lathes with steel–polymer concrete frame were built in three variants differing in polymer concrete filling distribution. Vulnerability of the machine tool variants to regenerative chatter instability was evaluated using frequency response functions calculated at tool-workpiece contact point. On the basis of the solution guaranteeing the highest stability of machining, a prototype lathe was built, subjecting model to experimental verification. The prototype lathe was characterized by up to 83% (on average 55%) reduction of relative tool-workpiece frequency response functions amplitudes, compared to steel variant.