The AD5X uses a quick-release nozzle that comes out without tools once the surrounding covers are open, which beats printers where the entire hot end has to be taken apart. The procedure is still worth doing carefully, since the nozzle sits close to a couple of small clips that are easy to pull the wrong way.
Start with the nozzle cold, or only warm enough that any loaded filament unloads cleanly. Forcing a nozzle change while it’s hot and loaded risks burns and a stuck strand of filament. Remove the front cover of the extruder, then take off the silicone sleeve wrapped around the heating block. With the sleeve clear, release the heatsink clip and the extruder clip holding the nozzle assembly in place, and the nozzle lifts out.
Installing the replacement is the same steps in reverse: seat the new nozzle fully, secure both clips, and refit the silicone sleeve before closing the front cover. Flashforge recommends running a nozzle temperature calibration and a full bed leveling pass right after any nozzle swap, since even a nozzle that seats properly can sit a fraction of a millimeter differently than the one it replaced.
The AD5X ships with a 0.4mm nozzle, and Flashforge also sells 0.25mm, 0.6mm, and 0.8mm options for finer detail or faster bulk extrusion. Whatever diameter you install, the AD5X’s maximum nozzle temperature is 300°C, and slicer settings should stay inside that limit regardless of what a filament’s datasheet lists as its ceiling.
One thing to be clear on: Flashforge describes the AD5X nozzle as adapted from the Adventurer 5M line to cut manufacturing cost, but the two are not interchangeable. Flashforge’s own FAQ confirms the mainboards and nozzle interfaces differ between the two printers, so a 5M nozzle won’t fit an AD5X and shouldn’t be assumed to work.
Choosing a replacement size is its own decision. The general guide to nozzle sizes beyond the stock 0.4 mm covers what changes in practice, and the comparison of brass versus hardened steel nozzles is worth reading before choosing a wear-resistant option for abrasive filament. Once the new nozzle is calibrated and printing cleanly, fold the swap into the regular maintenance schedule so wear gets caught earlier next time.