DIAGNOSIS The purge unit mechanism is jammed. This is the assembly that cleans the printhead. Paper debris or dried ink is blocking its movement.
FIX Unplug the printer. Open the front cover and the paper output tray. Look inside the right side of the printer. You will see a gray plastic assembly. Use a flashlight to check for torn paper scraps or hardened ink blobs. Use long-nose pliers to carefully remove any debris. Do not force any parts. Plug the printer back in. It will perform a startup sequence. The noise should stop.
IF THAT DIDN'T WORK The carriage assembly rail is dry. Unplug the printer. Move the printhead carriage by hand to the center. Apply one drop of white lithium grease to the metal rod. Move the carriage back and forth to distribute it.
HEADS UP The grinding can strip the gears in the purge unit drive. If cleaning debris doesn't stop it, power off immediately. The unit needs replacement.