Design of a Helical Variable-Angle End Mill for Thin-Walled Frame-Beam Components with Spatially Varying Stiffness: Machining Quality and Tool Wear

Frame–beam thin-walled components are widely used in aerospace equipment owing to their lightweight characteristics and high specific strength. However, their low and spatially non-uniform stiffness makes them susceptible to tool vibration and workpiece deformation during machining, posing considerable challenges in controlling deformation magnitude and maintaining uniform deformation across the machined region. To address the limitations of conventional end mills in machining frame–beam thin-walled components, a helical variable-angle end mill tailored to the spatial variation in workpiece stiffness was designed and manufactured. The rake and clearance angles of the proposed tool gradually increase from the tool tip toward the shank, progressively enhancing cutting-edge sharpness and reducing the cutting forces generated during machining. This geometric variation is designed to match the gradual decrease in workpiece stiffness from the fixed end toward the free end. Single-factor comparative milling experiments were subsequently conducted on a VDL850 machining center to evaluate the machining performance of the proposed tool. The results show that, compared with a conventional end mill, the proposed helical variable-angle end mill reduces the cutting force by at least 9.50%, flank wear by 77.78%, machining vibration by 25.17%, and machining error by 24.13%. These improvements reduce workpiece deformation and promote a more uniform deformation distribution across the machined region, thereby improving both machining quality and its consistency.