A CFRP/steel hybrid rotating shaft for a high-speed motorized spindle

Most key industry machines have a rotating structure for power transmission, which plays a crucial role in diverse engineering practices. In machine tools, a spindle is the heart of machining centers, and the quality of the spindle has a critical influence on overall machining errors across different manufacturing processes. Especially, axial growth due to thermal displacement of the shaft directly adds depth accuracy error of the tool. While additional compensation control techniques have been developed to cover such errors of spindles in practice, fewer efforts have been made to improve the actual amount of error in the spindle. This study introduces a new carbon fiber-reinforced composite (CFRP) fabricated hybrid design in a rotating shaft for a high-speed motorized spindle. With superior material characteristics of CFRP, it aimed to improve thermal displacement as well as light-weighting of the shaft. The developed spindle with composite shaft was tested in comparison with an equivalent spindle with a conventional single material shaft, and it achieved 18 % shaft weight reduction and 22 % improvement in shaft thermal growth. Furthermore, it was successfully tested in vertical face grinding of silicon carbide (SiC), providing accuracies over 99 %. Machining precision achieved conspicuous difference with 45.4 % enhancement at 3000 rpm and 27.3 % at 5000 rpm grinding. The significance of this study lies in that it suggests the first generalized method of adopting carbon fiber composite in rotating systems, including highspeed motorized spindles, which also proves its feasibility in actual machining.