Dimensional in Situ Shape and Surface Inspection of Metallic Micro Components in Micro Bulk Manufacturing

A rising trend to miniaturization and function integration requires new materials, tools, manufacturing setups and quality inspection strategies for mass production of micro mechanical systems (MMS). In most scenarios, quality inspection is carried out manually. An expert takes samples out of the manufacturing process and investigates them by means of tactile or optical measurement systems. This time consuming quality inspection process leads to low inspection rates, especially in bulk manufacturing processes, where manufacturing frequencies of 400 parts per minute are common. This contribution introduces an automated optical quality inspection method based on a digital holographic system, which acquires 2D texture and 3D shape information in one single measurement step. Based on 3D data, an automated point separation algorithm splits the measured object shape into elementary geometries and calculates form and position deviations compared to an object model. In the final step, a 2D surface inspection procedure based on multi-scale texture analysis detects surface defects with respect to the separated elementary geometries and fuses the result from the 3D shape and the 2D texture analysis to a final rejection decision. The capability of the proposed quality inspection method is demonstrated in a micro cold forming scenario, where a micro cup smaller than 1 mm in all geometric dimensions is the object under investigation.