|
In previous papers, we described a diagnostics tool for additive manufacturing products that is based on the concept that the acoustical/vibrational spectrum of an object can be used as a unique signature that characterizes the material and geometry of a product sufficiently to enable its comparison with a perfect reference to identify anomalies. This enables a user to identify rogue parts, such as defective, counterfeit, suspicious or problem parts such as defective or failing to meet specifications. The instrument produces a signature by measuring, with a laser Doppler vibrometer, the vibration of surface points on the part while it is energized by a swept frequency, piezo-electric exciter. Since its first introduction, additional research and development has enhanced, automated, and moved the instrument to a new level in terms of capability and ease of use. This paper describes the latest enhancements, including improved procedures and automation to enable use by an unsophisticated user with minimum training. The latest version provides automatic signal processing and comparison of acoustical signatures of reference and test objects that provide a quantitative grade for the object in terms of material properties, geometrical anomalies, and defects. This is achieved with specially developed algorithms that employ unique types of correlation of vibrational spectra taken from different objects or spectra produced by a simulation of a perfect object. The instrument can quickly produce an optimized correlation coefficient that serves as a numeric grade for a part for identifying suspicious or problem parts such as counterfeits, defective, or failing to meet specifications. The user can set acceptance criteria and initiate a pass or fail signal that can be used for large quantity inspections. Such an instrument is expected to find widespread applications in the AM industry.
|
