Quantification of Machining and Fixture Errors: 3D Method and Application

In the context of manufacturing precision, our interest is the 3D quantification of the manufacturing errors. This paper presents a measuring method of the manufacturing deviations. We sort the errors from machining operation and the errors of workpiece location. First, we present our method through an 1D model. We demonstrate with a statistical simulation that it is possible to identify separately these two kinds of manufacturing variations. To do so, we propose a double measurement of the workpiece. The first consists to probe the machining surfaces when the workpiece is always staying on the part-holder. The second consists to probe the machining and location surfaces of the workpiece (at the end of the set-up) with a coordinate measuring machine. Our current model for geometrical manufacturing simulation describes the geometrical errors of part surfaces with the small displacement torsor concept. The results of our method are torsor components variations. We have deployed our method through an industrial application. We compare two different kinds of workpiece fixture and we quantify 3D machining deviations. Thus we can select the best process plan which satisfies the required geometrical manufacturing conditions.