2019 Volume 60 Issue 700 Pages 147-152
In this paper, we present an inspection technology using Helmholtz resonance for small holes. As for the Helmholtz resonator, resonance frequency changes depending on the shape of the opening of the resonance container. The opening part is replaced with small hole parts and the hole diameter is inspected by measuring the resonance frequency of the inspection container. Small hole parts processed into a metal plate by press stamping or electric discharge method are the subject of examination. The prototype inspection system is constructed of a cylindrical container, a signal generator,and a sound signal analyzer. The container has a built-in standard microphone and speaker and resonance frequency is measured with respect to the container volume and sample hole diameter. The test sample of about 0.05 mm-2.0 mm in diameter had a hole formed by precision drill processing using planer-type jig borer and the electric discharge method. Test sample hole diameter inspection is enabled by measuring the resonance frequency and first fourier transform of measurement data.