Concentric hole drilling in multiple planes for experimental investigation of five-axis reconfigurable precision hybrid machine

Abstract

A five-axis machining center integrates two mechanical models: a three-degree-of-freedom parallel platform and traditional computer numerical control X–Y table. There is a trend for machining centers to be reconfigurable precision hybrid machine tools (RHMTs) for the fabrication of complex and precision products. Most industrial robots have open kinematic chains and serially connected links. A parallel manipulator is a closed-chain mechanism with two platforms (a base and moving platform) connected together by at least two independent kinematic chains. A parallel machine tool has the advantages of high rigidity, high precision, low inertia, and a simple mechanism. It is not easy to correct the errors in a five-axis machine tool. This paper focuses on the initial calibration of the static state errors, which consist of the errors from the component part machining, work-piece orientation, and mechanism combination. In an RHMT mechanism, a three-axis motion platform primarily controls the Z, α, and β freedoms. A laser displacement meter is fixed on the Z axis and measures the error in relation to the central position of the moving and fixed platforms when the x-y table is moved. The inverse kinematics of this mechanism will be revised, and an improvement will be made in the attitude precision of the moving platform. Finally, this paper discusses an experiment involving the drilling of concentric holes in multiple planes using an RHMT, and examines the cutting results from a coordinate measuring machine.