Analysis and Design of a Double-Chamber Centrifugal-Gyratory Mill for Fine and Ultrafine Comminution

This study presents the analysis, design, and experimental-numerical evaluation of a double-chamber centrifugal-gyratory mill developed for the fine and ultrafine grinding of mineral raw materials. The operating principle is based on plane-parallel circular motion of two cylindrical grinding chambers generated by a crank mechanism. This motion produces an intensified centrifugal field and promotes simultaneous impact, compression, abrasion, and interparticle breakage within the grinding zone. An analytical model was developed to evaluate the influence of crank radius, rotational speed, chamber geometry, and grinding-body mass on the forces governing material destruction. At a crank radius of 15 mm and a rotational speed of 500 min^-1, the calculated centrifugal force acting on a 7 kg grinding body reached approximately 288 N, which is 4.2 times greater than its gravitational force. This confirms that the investigated grinding process is controlled predominantly by dynamically generated centrifugal loading rather than by gravity alone. Physical grinding tests demonstrated the ability of the mill to fracture hard mineral samples under intensive operating conditions, confirming the practical effectiveness of the combined impact-compression mechanism. Structural performance was assessed using global and local finite element models developed in Autodesk Fusion. The complete double-chamber assembly, subjected to three applied moments of 900 N·m, exhibited a maximum von Mises stress of 22.915 MPa, a maximum displacement of 0.050 mm, and a minimum safety factor of 9.033. The local shaft-chamber-support model, analysed under a torque of 500 N·m, produced a maximum stress of 65.837 MPa, a displacement of 0.740 mm, and a minimum safety factor of 3.144. In both numerical models, the maximum stresses remained substantially below the assigned steel yield strength of 207 MPa. The combined analytical, experimental, and numerical results demonstrate that the proposed mill generates sufficient dynamic loading for hard-rock breakage while maintaining adequate structural strength, stiffness, and operational safety under high-torque conditions.