Forensic Analysis of a CNC Lathe Window Guard Failure

An analysis of an industrial lathe accident is presented in this paper. During operation, the rotating chuck lost its grip upon the cylindrical workpiece. The detached workpiece impacted the inside of the lathe cabinet, rebounded, struck the composite viewing window, and penetrated it. While observing the machining process through the window, the machinist was struck in the chest by the workpiece. He fell backward, suffering a severe traumatic brain injury when the back of his head impacted the concrete floor. The forensic analysis incorporated an event reconstruction to include an estimate of the ejection angle, velocity, and kinetic energy of the workpiece, the impact energy capacity of the window, and a failure analysis of the window and its frame. A kinetic energy analysis was performed by destructive testing of door/window replicas and high-speed vid-eography. Impact testing of exemplar workpieces against alternative design highly impact-resistant windows was also performed. © 2023, National Academy of Forensic Engineers. All rights reserved.