Different levels of each phenomenon in terms of acoustic emission (AE) correlated to deviation were characterised.

Physical phenomena using both the time and frequency domain analysis of the AE were gained from the vertical-axis micro milling tests.

Significant tool wear of micro milling was characterised after and before the onset of tool malfunction.

Different levels of the characterised phenomena were classified for the prediction of surface quality.

A real-time simulation displaying changing energy patterns as deviation errors increase/decrease was implemented.