Fault diagnosis of press dies using dynamic mode decomposition of a sound signal

• Published in: Journal of Advanced Mechanical Design, Systems, and Manufacturing Vol. 17; no. 3; p. JAMDSM0040
• Main Authors: KATO, Yuki, KUMAGAI, Rintaro
• Format: Journal Article
• Language: English
• Published: Tokyo The Japan Society of Mechanical Engineers 2023; Japan Science and Technology Agency
• Subjects: Amplitudes; Bearings; Compressed sensing; Damping ratio; Decomposition; Die pressing; Dynamic mode decomposition; Eigenvalue analysis; Eigenvalues; Fault diagnosis; Finite element method; Frequency analysis; Frequency spectrum; Gears; Press die; Propellers; Resonant frequencies; Vibration; Vibration analysis; Waveforms
• ISSN: 1881-3054; 1881-3054
• DOI: 10.1299/jamdsm.2023jamdsm0040

Although a wide range of machine failure diagnosis methods has been studied for bearings, gears, propellers, etc., there have been few studies on failure diagnosis methods for press machine dies. In this study, we develop a method to diagnose press die failure using a single microphone, which is easy to install, inexpensive, and robust. Because a damped vibration waveform is repeatedly observed in the processing noise of a press, general frequency analysis methods such as the FFT have a problem in that their spectra are blurred and only large amplitude vibrations can be detected from a frequency band comprising multiple vibrations. Therefore, we developed a method to perform dynamic mode decomposition by mapping repetitive vibration waveforms into a two-dimensional array. Based on the obtained eigenmodes and time characteristics, the main vibration components were identified using sparsity and extracted as failure diagnosis indicator values. It was found that the proposed method separates two vibrations that appear as a single peak in the frequency spectrum by the FFT. When this method was applied to the processing noise of abnormal and normal dies, a vibration component at approximately 200 Hz appeared only for an abnormal die. From the eigenvalue analysis of the material using the finite element method, it was realized that a 200-Hz horizontal mode was excited by the force in the direction orthogonal to the pressing direction owing to the die abnormality, resulting in the generation of a 200-Hz abnormal sound. Therefore, by monitoring the sound at the natural frequency of the material’s horizontal mode using the proposed method, die failure can be diagnosed. The proposed method can be applied to vibration analysis of structures and failure diagnosis of bearings, gears, etc., because the frequency, amplitude, and damping ratio of major vibrations can be obtained simultaneously.