Study On Parallel Machine Tools

Parallel machine tool is a new class of machine tool, which has received much attention from many researchers. The workspace analysis, error model, 3D modeling, motion simulation and auto-program of NC for an octahedron parallel machine tool and a new type of parallel machine tool are studied in this thesis.In this thesis an analytical method for workspace analysis of parallel machine tools is proposed. The analytical equations of workspace boundary surfaces for the octahedron parallel machine tool and the new type of parallel machine tool are derived based on the forward displacement analysis. Based on it, the projection graphs of workspace boundary surfaces are drawn. The results of analysis show that the workspace of parallel machine tools is enveloped by many surface patches.The error formulas of position and orientation for the octahedron parallel machine tool and the new type of parallel machine tool are set by using perturbation method. The position and orientation errors of moving platform are affected by driving bar errors, the structure errors of platform and the clearance errors of spherical joints. Based on it, the Monte Carlo simulation is implemented for the octahedron parallel machine tool, and then the statistical frequency histogram is given.On the platform of the 3DS MAX and MAX Script, the 3D modeling, motion simulation and interference analysis for the new type of parallel machine tool are developed in the virtual environment. Based on it, the reliable foundation is provided for checking the dynamic and static interference problems of machine tool structure design, verifying the rationality of path planning, and appraising thetechnological process and the rationality of the processing parameters of parts.Main-process and post-process are investigated to get the NC program of the new type of parallel machine tool. In the main-process, the coordinates of nodal points on part outline curve can be calculated by replacing this curve with a linear approximation. The codes expressed in NC program form which can be recognized by NC machine tool are got according to the coordinates of these nodal points in the post-process. The software system for a parallel machine tool with five degrees of freedom, which can be used to generate the NC codes in accordance with given cutter location data automatically, is developed based on VC++6.0.