Fixtureless profile inspection of non-rigid parts using the numerical inspection fixture with improved definition of displacement boundary conditions

Abstract

Quality control is an important factor for manufacturing companies looking to prosper in an era of globalization, market pressures, and technological advance. The functionality and product quality cannot be guaranteed without this important aspect. Manufactured parts have deviations from their nominal (CAD) shape caused by the manufacturing process. Thus, geometric inspection is a very important element in the quality control of mechanical parts. We have focused here on the profile inspection of non-rigid parts which are widely used in the aeronautic and automotive industries. Non-rigid parts can have different forms in a free-state condition compared with their nominal models due to residual stress and gravity loads. To solve this problem, dedicated inspection fixtures are generally used in industry to compensate for the displacement of such parts for simulating the use state in order to perform geometric inspections. These fixtures and the inspection process are expensive and time-consuming. Our aim is therefore to develop an inspection method which eliminates the need for specialized fixtures by acquiring a point cloud from the displaced part using a contactless measuring system such as optical scanning and comparing it with the CAD model for the identification of deviations. Using a non-rigid registration method and finite element analysis, we will numerically inspect the profile of a non-rigid part. To do so, a simulated displacement is performed using an improved definition of boundary conditions for simulating unfixed parts. In this paper, we will apply an improved method on two industrial non-rigid parts with free-form surfaces simulated with different types of displacement, defect, and measurement noise.