Forensic Analysis of A CNC Lathe Window Guard Failure




Lathe, Machine Guarding, Window Failure, Forensic Engineering, Hazard Analysis


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.


Ferdinand Pierre Beer and E. Russell Johnston, Vector Mechanics for Engineers. McGraw-Hill Science, Engineering & Mathematics, 1977.

Performance Criteria for Safeguarding, ANSI B11.19-2003, 2003.

Safety Requirements for Turning Centers and Automatic, Numerically Controlled Turning Ma-chines, ANSI B11.22-2002, 2002.

Safety Of Machine Tools - Small Numerically Controlled Turning Machines And Turning Cen-tres, BS EN 12415:2001, 2001.

Machine tools - Safety - Turning machines, ISO 23125:2010, 2010.

Machine tools - Safety - Turning machines, ISO 23125:2015, 2015.

D. Mewes and R.-P. Trapp, “Impact Resistance of Materials for Guards on Cutting Machine Tools—Requirements in Future European Safety Standards,” International Journal of Occupational Safety and Ergonomics, vol. 6, no. 4, pp. 507–520, Jan. 2000.

D. Mewes, O. Mewes, S. Augustin, P. Herbst, “Festigkeit von Werkstoffen bei Aufprall-beanspruchungen: Einfluss von Projektilwerk-stoff, -festigkeit und -form,” Materials Testing, 51(4):227-233, April 2009.




How to Cite

Batzer, Stephen. 2023. “Forensic Analysis of A CNC Lathe Window Guard Failure”. Journal of the National Academy of Forensic Engineers 40 (1).