Eggshell crack detection based on acoustic resonance frequency analysis

The human, visual inspection is the main quality control procedure in egg g rading. Eggshells are inspected for cracks and dirtiness on the shell and f or internal egg abnormalities, such as blood and meatspots. With the develo pment of high-speed electronic grading machines (>10 000 eggs/h per lane), this human candling operation has become a significant bottleneck. Recent r esearchinto the automation of the detection of eggshell cracks is focused b oth on optical and mechanical detection principles. In this research, eggsh ell crack detection is based on the analysis of the acoustically measured f requency response of an egg excited with a light mechanical impact on diffe rent locations on the eggshell equator. The optimal configuration of the eg g support, the location and design of the impactor and the response sensor are explored by means of an experimental modal analysis study of an intact egg. An egg with an intact eggshell responds by a characteristic frequency pattern that is highly repetitive when impacting on different places around the equator; the response signals' of cracked eggs are heterogeneous and n ot repetitive. This method allows a crack detection level of 90% and a fals e reject level of less than 0.5%. (C) 2000 Silsoe Research Institute.