Study on a Scan-to-CAD Workflow and Geometric Deviation Assessment of an Automotive Lower Control Arm

Abstract

This paper presents a case study on a scan-to-CAD workflow and geometric deviation assessment of a lower control arm in a double-wishbone suspension system. The component was digitized using an industrial blue-light optical scanning system, and the acquired data were processed in GOM Software and Geomagic Design X 19.2 to generate a mesh, clean the data, remove non-corresponding regions, and compare the scan with a reconstructed parametric CAD model in STEP format. Since the scan included the ball-joint stud whereas the reference CAD model did not, the comparison domain was trimmed before alignment and deviation analysis. Global geometric deviation was visualized by a color map with an in-tolerance range of ±0.5 mm, while three circular functional features, including two rubber bushing holes and one ball-joint mounting hole, were locally inspected on corresponding cross-sections. The results indicate that the main corresponding surfaces of the control arm body show good visual agreement, whereas larger deviations are mainly concentrated at boundary edges, curvature transition regions, and incompletely corresponding domains. For the three circular functional features, the displayed scan and CAD values coincide within the software display resolution: the two rubber bushing holes have diameters of approximately 17.000 mm, and the ball-joint mounting hole has a diameter of approximately 27.443 mm. These results confirm that the proposed workflow is suitable for digitizing, CAD reconstruction, and geometric inspection of suspension-arm-type mechanical components when the original CAD model is unavailable.