Abstract: Employee #1 reached into the work area of a semi-automated multiple point, spot welding machine to reposition a mis-set piece, and a clamp closed on her hand. The employee sustained multiple fractures to her left thumb. Her hand was caught under a parts clamp that moved unexpectedly after an emergency stop default was initiated by a photoelectric presence sensing device that was interrupted. The compressed air-powered actuating ram, which closes the clamp, remains pressurized when the emergency stop is activated. The clamp became stuck against the mis-set part at the start of the machine cycle causing a process default to stop the welder. The pneumatic ram stores pressure (energy) that enables movement even with the emergency stop default. The machine's ID # is FWS-0606.