Date of download: 12/22/2017 Copyright © ASME. All rights reserved. From: Online Real-Time Quality Monitoring in Additive Manufacturing Processes Using Heterogeneous Sensors J. Manuf. Sci. Eng. 2015;137(6):061007-061007-12. doi:10.1115/1.4029823 Figure Legend: (Top) The three observed process states in FFF, demarcated as normal, abnormal, and failure. (Bottom) The transition between normal, abnormal, and failure states is prominently evident from the time series pattern of the noncontact IR temperature sensor.