Focusing tube operational vibration as a means for monitoring the abrasive waterjet cutting capability

Abrasive waterjet cutting is a competitive manufacturing technology in the aerospace, defense and automotive industries which, as power users, require state of the art process performances in terms of stability and product assurance, due to their demanding quality standards. Meeting such requirements is a relevant technical challenge for abrasive waterjet cutting, due to insufficient monitored data and intrinsic process instability. The present paper describes an innovative approach based on non-invasive vibration sensors, for monitoring the jet cutting capability. This result is allowed by the experimental evidence proving that the operational vibration monitored by means of two accelerometers installed at the tip of the focusing tube is well related to the kinetic power of the abrasive particles, i.e. the only portion of the jet power that is responsible for the material removal in abrasive waterjet cutting. The approach is validated by means of an experimental investigation, in which the abrasive waterjet is fired at different water pressures and abrasive mass flow rates, providing different kinetic powers. The information delivered enriches the process knowledge, thus paving the way to significant improvements ranging from closed-loop control strategies for the water and abrasive feeding systems to actions for supporting operators in compensating drifts of the jet cutting capability. The expected impact is an improvement of process automation and stability, as well as an enhanced process traceability.