Unscrew and remove the pen cap. Then unscrew and remove the outer pen barrel from the pen-point and ink cartridge.
Unscrew the colored ring and remove it from ink cartridge. Pull off the ink cartridge with a slight twist.
Spill any residual ink that hasn't dried onto a folded paper towel or rag by tapping cartridge's closed end.
Separate the pen nib from the black pen carriage using a nib-key to unscrew it. The nib-key is the small wheel tool that's included in most technical pen sets. There are usually two of these keys in a set.
Thread the pen nib using a pressure bulb cleaning syringe.
Place nib, ink cartridge, and all other pen parts that may contain dried ink into a small bowl. Pour pen cleaning solution (or simple dish soap and water) into the bowl, covering all pen parts. Let them soak overnight.
Rinse all parts with hot water. Dry them off with a clean paper towel or rag. Reassemble the pen.