MACHINE TOOL DIRECT ERROR BUDGETING BY VIRTUAL MACHINING

摘要

Today's machine tool builders use different machine layouts to increase productivity and accuracy. A considerable improvement of these two machine characteristics has been reached by the steady quality increase of machine tool components and CNC controls. Modern CNC control systems have the power and memory, not only to perform direct control of machine movements, but also to compensate for machine tool mechanical errors. As long as these errors are repeatable and relatively small, they can be compensated successfully. These requirements set the maximum allowed deviation on straightness, squarness, and positioning accuracy (kinematic errors measured in cutting point) for machine tool slides. Metal cutting is a complex process where the cutting force variation depends on several external variables such as: friction, vibrations, material homogeneity, tool material, tool edge, etc. These force variations have to be counteracted by the machine tool structure, which means it has to have high static and dynamic stiffness. We can summarize these requirements as: - Low geometrical and kinematical error; - High static and dynamic stiffness of machine structure (including drives).