Hierarchical design, laboratory prototype fabrication and machining tests of a novel 5-axis hybrid serial-parallel kinematic machine tool

摘要

Hybrid serial-parallel kinematic machine tool (HSPKMT) has been regarded as a promising solution for 5-axis machining in many industrial fields. A typical HSPKMT can be constructed by integrating a parallel functional module with a serial functional module. Following this way, the authors construct a novel 5-axis HSPKMT through the integration of an over constrained redundantly actuated parallel module with a stack-up serial gantry. The proposed HSPKMT can accomplish a 5-axis motion capacity with three translations and two rotations (3T2R). A hierarchical design method is proposed to facilitate the design issues of the 5-axis HSPKMT. According to the hierarchical method, a laboratory prototype is designed with a top-down strategy and then fabricated with a bottom-up strategy. An open-architecture computer numerical control (CNC) system is developed to drive the fabricated prototype. A kinematic analysis is carried out to reveal necessary kinematic properties of the proposed HSPKMT. The reachable workspace and task workspace are defined to graphically illustrate the machine's position-orientation capabilities. A workspace performance index is formulated to compare the proposed 5-axis HSPKMT with several 5-axis machine tools. Based the kinematic analysis, a 5-axis machining methodology is developed and further applied to the laboratory prototype to perform 5-axis machining tasks. The machining tests verify that the proposed novel HSPKMT possesses desirable 5-axis machining capability with the tolerance rang of +- 0.05 mm. This also implies that the proposed hierarchical design method as well as the 5-axis machining methodology can be further applied to other types of HSPKMTs with minor modifications.