Optimal Structure Design Methodology for Compound Multiaxis Machine Tools - II - Investigation of Basic Structure -

Compound multiaxis machine tools are used to machine high-value-added parts through integrating milling and turning. Compound machine tools are generally structured based on a conventional NC lathe by incorporating Y axis and automatic tool changer (ATC) components for milling. Due to complexity of the structure and functional versatility required for a compound machine tool, accuracy, productivity, and return on investment (ROI) must be improved over conventional NC lathes and machining centers. In the sections that follow, we discuss design methodology for compound multiaxis machine tools, focusing on the design of an optimal basic structure for high accuracy and high productivity. We propose a box in box structure, a movable column-Y axis, and a boring machine structure. We analyzed static rigidity, dynamic features, and movement accuracy of machine structures theoretically using FEM for three proposed structures. We found that the box in box structure is suitable for compound multiaxis machine tools to achieve high accuracy and high productivity.