Error analysis of free-form surfaces for manufacturing applications

Error analysis of free-form surfaces is a requirement to assure quality and to reduce manufacturing costs and rework. This paper proposes a new approach and algorithms for the error analysis of free-form surfaces. Given the measured surface as an input the approach first uses a statistical method to determine the number of test-points with suitable sample size for shape error analysis. Then, the system applies a robust mathematic model, Implicit polynomials (IP), to construct the model of the test-points. To perform detailed comparison of the shapes, the CAD model is geometrically adjusted with the input using model-based matching algorithm developed in this paper. Once the CAD model is adjusted, it is compared with input to reveal the errors between their shapes. To accomplish this task a new shape matching algorithm is developed. Experimental results on error analysis of a variety of the machined metal skin of aircraft are reported to show the validity of the proposed methodology.