Fully-automatic surface inspection of O-ring seals

Polymer seals are used throughout the automobile for a variety of purposes, and the consequences of a failure of such a seal can range from annoying in case of an A/C component to catastrophic in the case of brake components. With the constantly increasing demands for these components regarding e.g. pressure, tighter tolerances or new refrigerants come more stringent requirements for ensuring surface properties according to the specification for the specific application. While automatic inspection systems are available for a variety of defects, the area of seal inspection is still dominated by manual labor, partly because handling of these small, inexpensive parts is difficult and partly because visual coverage of the entire sealing surface poses a problem. It is also difficult for a human inspector to objectively assess whether or not a surface defect is critical, especially given that inspection of each seal must be completed within a few seconds. The high cost of manual labor can also result in unnecessary delays if quality assessment has been outsourced. This paper describes a fully automatic optical inspection system for ring sealing surfaces using sheet-of-light laser measurement and custom image processing on PC hardware keeping pace with production. The paper presents the system concept and the experiences gained using this system at the plant of one of the world's largest producers of hydraulic seals