Datum selection methods and systems for minimizing hole position errors in group hole machining of large components

A datum selection method for minimizing hole position errors in group hole machining of large components, comprising:

• (1) determining a type of a computer numerical control (CNC) machine tool, and establishing a topological structure of the CNC machine tool with respect to a motion unit of the CNC machine tool;
• (2) establishing a theoretical postural model of a tool center point during a motion of the motion unit of the CNC machine tool according to the topological structure established in step (1);
• (3) according to the theoretical postural model in step (2), establishing a hole position error model based on a distance between an actual position of the tool center point and a theoretical position in the theoretical postural model of the tool center point during a hole making process and by means of a projection relation of a plane perpendicular to an ideal axis;
• (4) establishing an average error model of hole positions according to a datum selected from a machining form of group holes of components and in conjunction with the hole position error model obtained in step (3);
• and
• (5) obtaining the average error model obtained in step (4), applying a partial derivation to variables of the average error model, and obtaining a machining datum of group holes of the corresponding components.