Resonant inspection (RI), the general classification of Resonant Acoustic Method (RAM) nondestructive testing, is commonly used for 100% quality assurance testing of ductile iron cast, powder metal (PM), and metal injection molded (MIM) components, providing a volumetric whole body approach that detects both external and internal structural flaws and anomalies. This technique measures a metal component’s mechanical resonances by impacting a part and analyzing the acoustic ringing produced against a template generated from a statistically significant sample of “good” parts. These mechanical resonances are defined by material, mass and stiffness—with sensitivity to both structural flaws and process consistency. Process variations due to manufacturing variables can present as much of a significant challenge, if not more, as structural defects themselves. NDT-RAM allows for both online quality assurance testing for structural flaw and anomalies and benefits manufacturing consistency as a process gauge, including the ability to meet or exceed the user’s Six Sigma quality goals and drive for continuous improvement.
Dr. W. Edwards Deming’s “Fourteen Points for the Transition of Management,” states that a focus on quality throughout every level of a company drives expenses and costs down while increasing productivity and market share. A singular dependence on inspections has the opposite effect—costly, unreliable systems that never eliminate the source of the variations. As illustrated in the case study below, resonant “inspection” based on NDT-RAM has been used successfully as a continuous process monitor, resulting in the elimination of the sources of variation and serving as a guidepost to process improvement.