Hybrid Quill Shaft for a Multifunctional Portal Machine Tool Centre

A hybrid quill shaft for a multifunctional machine tool centre combines a conventional steel body with a wound composite insert that significantly enhances structural stiffness and dynamic properties. This paper presents a methodologically rigorous approach to the design and validation of a hybrid quill shaft, encompassing material optimisation through the NSGA-II evolutionary algorithm, experimental modal analysis, and verification of the influence of an active pre-tensioning anchor system on the compensation of elastic deformations. A finite element model was coupled with an optimisation tool evaluating eight fibre types across 786 iterations. Results unequivocally demonstrated the superiority of M55J fibre with ±88° orientation as the optimal compromise between stiffness (13.2% reduction in deflection), weight (3% reduction), and cost (4.2% cost increase). Composite safety was ensured through the three-dimensional Tsai-Wu strength criterion applied as a constraint. Experimental validation on an assembly with a hydraulic pre-tensioning system demonstrated symmetrical quill shaft behaviour (±0.07 mm/m) and agreement with finite element analysis (9.5% deviation). Numerical modal analysis revealed a pronounced decrease in natural frequencies with increasing overhang (from 308 Hz to 58 Hz). The resulting design incorporating M55J fibres, 2345 mm length, and epoxy resin in a 60:40 fibre-to-matrix ratio represents a practically implementable solution for enhanced precision and productivity in modern machine tool centres.