Abstract: Based on the error influence tracing analysis for complex machine tool has been carried out based on “S” shaped workpiece. A method of judging the error parameters which is the biggest influence on machining defects is established. In this method, the machining defects of “S” shaped workpiece and shaping motions of complex machine tool are comprehensively considered. Cubic B-splines surface has been applied to surface representation. The actual position of tool center can be deduced by projecting the B-splines surface in its normal direction. The mapping relationship between the actual tool position and the actual machining curve is established. The machining defects generation model is established. The error expression equation has been deduced. Those 5 key parameters that have great influence on processing defects are determined according to the contribution which have been computed using the sensitivity and measured values of error parameters. Experimental results demonstrate that the error of each point is not more than±1.5 μm by comparing the five error parameters and all parameters under the action of at the same time. The biggest errors which influence on the machining defects are, , , , .

Key words: “S” shaped workpiece, error tracing, machining defect, sensitivity, complex machine tool