Abstract: Employee #1 was operating a cuber machine at a concrete block manufacturing facility. The automatic cubing machine stacks and palletizes the blocks; a UPC tag is then placed between the blocks before they are moved into the storage yard on a conveyor. The machine is normally guarded at the rear with an expanded metal guard attached to the conveyor frame by a metal hook. In the weeks prior to the accident, the guard was opened and a pedestal floor fan was placed between it and the opening into the storage yard. The fan was meant to keep the colder outside air from entering the building and fogging the photoelectric beam that caused the machine to cycle. Employee #1 was between the fan and the open guard, placing tags between the blocks as the machine was stacking them. The machine cycled, and a sliding metal part struck Employee #1 on the head. He jumped back, and his head struck the return side of a clamp. The clamp squeezed down on the sides of his head, fracturing his jaw and lacerating his chin and ear. Employee #1 was extricated from the machine by his supervisor.