Elegoo Neptune 4 Max: 24 Known Issues and Fixes

The Elegoo Neptune 4 Max is an open-frame bedslinger with a 420×420×480 mm build volume, a 300 °C hotend, a bed that stops at 85 °C, and a Klipper build Elegoo locked down. Here are 24 problems that belong to the Max specifically — from a bed that tacos on you to a 350 W power supply that cooks itself feeding that enormous heater.

Issues shared by the whole family — bed mesh, proximity probe, Klipper quirks — are covered in 22 known issues of the Elegoo Neptune 4 and 28 problems of the Neptune 4 Pro. This article is about what the size itself breaks: a 420×420 mm plate, a heavy 430×430 mm bed, two Z motors, no endstops, and a heater that never gets enough power.

1. Two Neptune 4 Max revisions, and firmware doesn't cross between them

Two different machines ship under one name: the original Neptune 4 Max with a ribbon cable to the toolhead, and the Neptune 4 Max+ with a USB-C port and a coiled extruder communication cable. Their firmware packages are different, and mixing them up is the fastest way to brick the printer. Both warnings live in Elegoo's own documents: the Neptune 4 Max FAQ and the How to use the fix pack page.

1. Check the front panel: a USB-C port and a coiled extruder communication cable instead of a flat ribbon mean you own the Max+
2. Confirm the SN on the white label under the left front of the bed — the format is NEP X.XXXXX.XXXXX and the model reads as NEP 4 Max
3. Download firmware only from the section matching your revision in the Elegoo Download Center
4. The Max+ has no fix pack at all — it only takes mainboard and screen firmware from its own branch
5. The Max+ also has its own error, "mcu THR: Unable to connect", which points at the extruder communication cable rather than the board

2. Update order: fix pack first, then mainboard, then screen

Neptune 4 Max firmware comes in three parts, and the order isn't advice — it's a requirement. If the mainboard is older than V1.2.2.65 you flash the fix pack first, and only then the mainboard and the screen. The two versions must match: 1.2.2.64 pairs with 1.2.11, 1.2.2.65 with 1.2.12, 1.2.3.0 with 1.2.13, 1.2.3.1 with 1.2.14, and 1.2.3.2 with 1.2.14. The table and the procedure live on the mainboard and screen firmware page.

1. USB drive: FAT32, under 16 GB. TF card: FAT32 with a 4096-byte allocation unit, under 32 GB
2. Drop the ELEGOO_UPDATE_DIR folder in the root of the drive, plug it in, power up and wait for the reboot
3. Check the drive for fix_klipper_successed and fix_tag — without those two files the fix pack didn't land
4. Mainboard: Settings → About Machine → Update → Confirm, roughly two minutes; an update.log file on the drive confirms success
5. Screen: .tft file in the root of the TF card, card into the slot on the screen board behind the four-screw back cover, gold contacts facing up
6. After the update: auto leveling, Z-offset, Input Shaper X and Y, and only then printing
7. Back up your printer.cfg edits first — the update overwrites them

3. Updating Klipper from Fluidd bricks the printer

The Neptune 4 Max runs a customized Klipper build, not vanilla. Hitting "Update" in Fluidd, upgrading Moonraker, or flashing an MCU binary built by stock Klipper kills the machine. The community hardware documentation for the Neptune 4 spells it out in capitals: do not flash the MCU with a Klipper-generated bin.

If the printer is already dead there's a serial route, documented by an owner in the ElegooFix repository on GitHub. In his case an official firmware file killed the Max, Elegoo shipped a replacement mainboard, eMMC module and screen — and a fresh firmware package crashed Klipper again. Serial was what finally worked.

1. Try the supported path first: the fix pack from a FAT32 drive under 16 GB
2. If that fails, connect your computer to the printer's USB-C port with a data-capable cable (plenty of charging cables aren't)
3. Find the device with dmesg | grep tty and connect: screen /dev/ttyUSB0 115200
4. Log in as mks with the password makerbase — those are the stock MKS board credentials
5. Edit the .deb filename inside update.sh to match your package and run sudo ./update.sh
6. Last resort: pull the eMMC module and flash the image through an adapter

4. The screen hangs on the splash and the printer calls itself a "Neptune 4"

Two symptoms, one root cause. Either the screen spins the ELEGOO splash for more than a minute, or it jumps straight into settings where the mainboard firmware field is blank and the model reads Neptune 4 with a 225×225×265 mm volume. The printer can't see its own board.

The first thing the Elegoo wiki checks is a short in the accessories. Unplug four things at once: the USB drive, the filament runout sensor, the gantry LED and the Y accelerometer cable. If the menu comes back, plug them in one at a time and you'll find the culprit.

1. Power down and remove the USB drive, the runout sensor plug, the gantry LED and the Y accelerometer cable
2. Power up: if the menu loads, reconnect one cable at a time until it hangs again
3. Flash the fix pack from a USB drive and wait about two minutes after power-on
4. Verify that fix_klipper_successed and fix_tag appeared on the drive
5. Update mainboard and screen firmware immediately afterwards — don't print before that
6. Still dead: the eMMC, the mainboard or the screen needs replacing; you can borrow a screen from any other Neptune 4 series printer to test

5. The 420×420 bed tacos and the center has nothing to adjust

This is the Max's signature pain. Adjustment screws sit around the perimeter plus two in the middle, and owners keep reporting the same thing for years: you can dial in the edges, but the middle of the plate simply doesn't come up. As one two-year owner put it: "even when both sides are fully leveled, the center is unadjustable".

The numbers are well documented: 0.2 mm of deviation in the front-left corner in one hands-on review, close to 200 microns right along the edge in another, up to 0.3 mm for an owner on a Russian forum. And part of the taco is self-inflicted — overtightened bed screws bend the plate into a curve all by themselves.

1. Pull the PEI plate and inspect the aluminum bed itself for warping, debris underneath or impact marks
2. Back all bed screws off to the same tension — never crank them down
3. Through Fluidd, add a screws_tilt_adjust section with your screw coordinates to printer.cfg
4. Run SCREWS_TILT_CALCULATE on a hot bed until no screw needs more than 5 minutes of rotation
5. Turn on an adaptive mesh — KAMP or Adaptive Bed Mesh in OrcaSlicer — so the printer stops probing 121 points for a 10 cm part
6. If the plate is physically bowed, send Elegoo support photos and your mesh map

6. Bed springs drift and the screws back themselves out

There are six springs and six wheels under the Neptune 4 Max bed. A spring is a soft part: it compresses as the plate heats, wanders with the vibration of a heavy moving bed, and won't hold level between prints. On top of that, the adjustment screws loosen over time on their own.

1. Buy a set of silicone spacers and swap out all six springs
2. Compress the spacers about a third of the way, evenly across every point
3. Fit lock nuts or printed retainers to the adjustment screws
4. Re-run screws_tilt_calculate and reset the Z-offset afterwards

The payoff is worth an evening of work: one owner who fitted spacers and permanent mounts reports a year and a half without re-leveling, and another logged 233 print hours on one mesh after adding spacers, KAMP and screws_tilt_calculate.

7. Leveling a cold bed is pointless: 13 minutes to reach 85 °C

The Max carries a huge aluminum plate that heats slowly and unevenly. Measured times from a hands-on review: about 5 minutes to 60 °C and roughly 13 minutes to 85 °C. Level it cold and the geometry moves as it heats, which puts you right back to chasing the first layer by hand.

1. Set the bed to printing temperature and let it soak for 20–30 minutes before leveling
2. Only then run auto leveling and the Z-offset calibration
3. Against probe thermal drift Elegoo suggests heating the bed to 60 °C and waiting about 20 minutes
4. If your room is colder than 25 °C the bed won't even reach its rated 85 °C — you need an enclosure
5. Keep the auxiliary fan off until the bed is at temperature: it blows the heat straight off the plate

8. The Z-offset drifts between prints and won't stay saved

TechRadar dialed the Z-offset to 0.47 mm and noted that although the printer says the value is saved, it still needs tweaking at the start of every print. Tom's Hardware went further: the reviewer stopped trusting on-screen leveling altogether and sets Z through Klipper's web interface instead.

One Neptune 4 Plus owner traced the failure through the Fluidd console: the bed mesh loads fine, but the Z-offset set during leveling never gets applied, and a G28 wipes it again. Hence the community rule of thumb — the Z-offset only behaves when you adjust it from the printer's own screen, not from the slicer.

1. Check for play on X and Y and snug the eccentric nuts up about a third of a turn at a time
2. Make sure the POM wheels at the ends of the X axis aren't overtightened — that makes the Z axis bind on the way up
3. Loosen the lead screw brass nut screws: the manual says they must stay slightly loose
4. Measure both ends of the X axis to the bed with a ruler and get the gantry parallel
5. Inspect the proximity probe: connector, tilt, mounting screws
6. Heat soak the bed and set the Z-offset again — from the screen only, in 0.01 or 0.1 mm steps

9. The probe only sees metal: without the PEI plate the nozzle digs in

The inductive proximity probe only responds to the metal plate. Run Home or Level on a bare bed with the PEI plate removed and the nozzle will drive straight into it — there's simply nothing for the probe to detect. It's one of the most common support questions on this model.

1. Confirm the PEI plate is on the bed and seated flat, with no lifted corners
2. Confirm the nozzle is a genuine Plus/Max part, not a generic V6 or MK8: a different length shifts the trigger point
3. Power down and inspect the toolhead connector pins — straighten bent ones carefully with tweezers
4. Reseat the probe connector and check it for tilt and loose mounting screws
5. Tighten the hotend mounting screws: a sagging assembly moves the probe relative to the nozzle
6. Temporarily set the Z-offset to 0 to separate a mechanical fault from a settings problem

10. The nozzle is custom: V6 and MK8 don't fit

The official Max FAQ is blunt about it: the nozzle uses a customized design and isn't compatible with nozzles of other specifications. Part numbers for Plus and Max are B0N0R1, B0N0S1 and B0N201, with B0N0Q1, B0N1X1 and B0N3A1 for the complete assembly. Generic "fits everything" kits don't work here, and a wrong nozzle also breaks auto leveling.

1. Buy nozzles explicitly listed for Neptune 4 Plus / 4 Max, or by part number B0N0R1, B0N0S1, B0N201
2. Use hardened steel for carbon-filled, glow-in-the-dark and glitter filaments
3. Elegoo suggests inspecting the nozzle every 1–3 months: PLA wears it slowly, PETG and composites quickly
4. Swap the nozzle hot and torque it hot
5. Always reset the Z-offset and re-run auto leveling after a nozzle change

11. No X and Y endstops — the printer finds zero by crashing

This is a design decision on the Plus and Max that never made it into the product description. The Elegoo wiki explains it: these models drop the limit switches and read zero from the torque spike when the belt and motor slam into the stop. That's why homing is loud, and why "the motor doesn't stop but keeps crushing" is a stock complaint.

Tom's Hardware called out the painfully loud sensorless homing, with the machine ramming its X and Y stops. Elegoo fixed part of that with firmware updates, but firmware can't undo the mechanical cause — a belt that's too tight to let the stop register.

1. Loosen the belt on the axis that keeps crashing: turn the tensioner knob counterclockwise
2. Make sure nothing obstructs the carriage or the bed and the extrusions are clean
3. Update mainboard and screen firmware as a matched pair
4. If the screen shows "No trigger on x after full movement", swap the X and Y motor connectors with the printer off: if the error follows the swap it's the motor, if it stays it's the board

12. The bed wobbles: six wheels and non-parallel Y extrusions

The Max bed carriage rides on two aluminum extrusions on six POM wheels. If those extrusions drift apart, no amount of eccentric adjustment will take the wobble out. Check it with a ruler: the distance between the extrusions must match front and back, and the community reference is 140 mm at both ends.

1. Measure the gap between the Y extrusions at the front and at the back
2. If they match, adjust the wheel eccentrics roughly 1/6 to 1/3 of a turn at a time over several passes
3. If they don't, remove the drawer, the screen and the bottom cover, loosen the eight extrusion screws and square them up
4. Re-check tension after long prints — owners report wheels loosening after every big job
5. Worn wheels get replaced as a set; the part costs pocket change

13. Belt tensioners crack, and an overtight belt overheats the driver

Elegoo's own layer-shift page for the Max lists "X/Y belt tensioner damaged" and "belt too tight" as separate causes. The tell is simple: the bed or carriage is hard to push by hand and the belt rings like a guitar string. An overtight belt is also the first listed cause of the Y driver overtemperature error.

The tail of the Y belt deserves its own warning. One reviewer lost his first print to it: the belt end had been hooked over the retainer with slack, and it only seated properly once the bed started slinging back and forth. The same reviewer added tension to the bed belts afterwards — a plate that heavy was leaving ringing on the walls.

1. Push the bed and the carriage by hand: both should move freely and the belt shouldn't ring
2. Loosen belts by turning the tensioner knob counterclockwise
3. Pull the X tensioner cover (two screws, 2.0 mm hex) and check the tensioner for cracks; repeat for the Y tensioner
4. Replace a cracked tensioner immediately — it gives you floating tension and layer shifts
5. Check the pulley set screws: some batches ship without them, and where they exist one screw must face the flat of the motor shaft
6. Make sure the belt tail is seated fully into the retainer, not left with slack
7. Print rotation stops for the tensioner knobs so tension can't creep

14. An 85 °C bed: ABS, ASA and nylon exist only on the product page

The Elegoo store page promises PLA, TPU, PETG, ABS, ASA and nylon. The official FAQ for the same machine in the wiki answers more briefly: PLA, PLA+, TPU, PETG. The difference comes from the bed ceiling — 85 °C, and only with an ambient temperature around 25 °C. The Neptune 4 Pro bed reaches 110 °C and the Neptune 4 Plus 100 °C; the Max got capped at 85 °C.

Practice sides with the FAQ. 3DWithUs couldn't print ABS brackets on the Max: the part tore off the plate mid-print even with Magigoo and a brim, and they moved the job to an enclosed machine. The same brackets in PETG printed flawlessly.

1. The Max's working materials are PLA, PLA+, PETG and TPU — that's what it was built for
2. Large ABS and ASA parts need an enclosure of at least 658×980×955 mm
3. For fussy PLA and PETG raise the bed 5–10 °C above the number on the spool label
4. Print the first layer at 15–40 mm/s with a line width of 120–150 % of the layer height, as the wiki suggests
5. Keep the auxiliary fan off until the bed reaches temperature

15. The 350 W power supply runs flat out and burns up

In March 2026 an owner posted photos of a burned-out Neptune 4 Max power supply with the line "I'm glad the fire was contained". The thread explains the physics: the failed part was the NTC inrush limiter, and the factory 350 W unit was never meant to run at 350 W continuously. A 430×430 mm plate acts like a radiator, so with a hot bed or a cool room the heater is on almost non-stop.

1. Check the mains selector: 115 V for a 110–120 V grid, 230 V for 220–240 V. Some batches ship with a sticker over it — leave those alone
2. Don't leave long hot-bed prints unattended, especially in a cool room
3. Check the input fuse — AC 250 V / 10 A
4. Confirm the PSU fan spins: it runs the whole time power is applied
5. In warranty Elegoo replaces the unit; out of warranty owners fit a 500 W or larger supply

16. The auxiliary fan is either off or blowing parts off the plate

A bar of auxiliary fans sits on the Max gantry. It has no independent software control: it's wired in parallel with the part cooling fan, and all it owns is a physical button on top. One reviewer removed the bar entirely, describing it as having "only two states: off, and blowing every scrap of paper off the bed at full power".

With PETG the bar hurts twice over: the plastic warps from too much cooling, the edge lifts, catches on the fan and the part gets ripped off the plate. Owners simply switch it off for PETG. For PLA at high speed it's genuinely useful.

1. Switch the auxiliary fan off with the physical button on top when printing PETG
2. Leave it on for PLA at high speeds
3. Never run it before the bed reaches temperature
4. Use the print modes: Silent for long PETG jobs, Sport for detailed PLA
5. If the fan won't spin, check the button first, then the connector and the toolhead ribbon

17. The runout sensor drags on the filament and wears through

One Max owner posted a runout sensor whose brass guide had been sawn clean through with under 150 hours on the machine — and he'd only ever run PLA. Others in the thread confirmed the same wear on Neptune 3 and other Neptune 4 machines.

The cause isn't abrasive filament, it's geometry. The filament travels from the spool to the toolhead through the sensor, and every acceleration jerks a heavy spool while the strand saws across brass at an angle. A reviewer fixed it with a length of PTFE tube between the extruder and the sensor: with it, nothing drags on the carriage during travel moves.

1. Run a length of PTFE tube between the sensor and the toolhead to take the side bend out of the path
2. Confirm the spool unwinds freely and the filament feeds over the top, not from underneath
3. Inspect the brass guide: a visible groove means the assembly is done
4. Check the sensor more often when running abrasive filaments
5. Don't need it? Leave it unplugged — with no sensor at boot the printer simply ignores it

18. The blob of death and the two sides of the PEI plate

A blob of death starts when a part comes off the plate, sticks to the nozzle and grows into a lump of plastic around the whole toolhead over a couple of hours. It happens regularly on the Max, and for beginners the cause is usually the same: printing on the wrong side of the plate. The Neptune 4 plate is double-sided and the sides are not interchangeable.

1. Print PETG on the side of the plate meant for it
2. Wash the plate with warm water and dish soap, not just 75 %+ isopropyl alcohol
3. Verify the nozzle is torqued hot: oozing from the top of the assembly leads straight to a blob
4. Catch it in the first layers — the lump grows while the detached part rides along with the nozzle
5. Already happened? Heat the assembly and pull the lump off with pliers; a heat gun melts the plastic extruder housing
6. If fans and the thermistor got caught in it, replace the toolhead as an assembly

19. The printer shows no model thumbnails

A small thing that annoys you daily: thumbnails only show for the files that shipped on the bundled USB drive, while anything sliced in Cura or PrusaSlicer displays the manufacturer logo instead. Reviewers flagged it too. The fix is a plugin that Elegoo itself documents in the wiki.

1. Cura: download the ElegooNeptuneThumbnails .curapackage from the Molodos releases on GitHub, drag it into the Cura window and restart
2. PrusaSlicer and OrcaSlicer: download the ElegooNeptuneThumbnails-Prusa.exe post-processor into a folder that doesn't need admin rights
3. Point the Post-Processing Script field at it
4. In OrcaSlicer set G-code flavor to Marlin (legacy) and the thumbnail to 600×600 PNG
5. If you aren't using the official printer preset, append --printer= after the script path

20. "Move exceeds maximum extrusion" on your very first file

The full message reads "Please run SDCARD RESET FILE or FIRMWARE RESTART to resume. !! Move exceeds maximum extrusion", and the print dies almost immediately. The official wiki lists exactly two causes, both in the slicer: the wrong printer profile, or relative extrusion left off.

1. Match the printer in your slicer to the SN on the white label under the left front of the bed: NEP 4 Max is a Neptune 4 Max
2. Enable relative extrusion in the special modes section of the slicer
3. Re-slice and upload the new .gcode
4. Files sliced for the Neptune 3 series won't run on a Neptune 4 — the wiki calls this out explicitly
5. Still failing? Update mainboard and screen firmware as a pair

21. The nozzle scrapes the infill and knocks the part loose

This is the single most common Max complaint: the first layers look perfect, then infill starts and you get grinding, gouges and eventually a part torn off the plate. Elegoo's layer-shift page explains the mechanism — patterns like Grid cross over themselves constantly, at speed the nozzle slams into already-cooled lines, resistance spikes and the motor skips steps.

The second scenario is over-extrusion: the layer ends up taller than planned and the nozzle catches it on every pass. That's why calibration has a strict order — extruder rotation distance first, then flow and maximum volumetric speed, and everything else after that.

1. Switch infill from Grid or Triangles to Gyroid or Cubic
2. Enable Z-hop in Normal mode rather than Slope, plus "Avoid crossing walls" in OrcaSlicer
3. Calibrate extruder rotation distance, then flow — over-extrusion produces the same grinding
4. Give supports a brim and more bottom layers: without a brim the nozzle knocks them over
5. Drop to 150–250 mm/s on large parts
6. Check that the Z brass nut screws aren't fully tightened — a binding Z axis rubs the nozzle across the model

22. Input Shaper calibration fails with an accelerometer error

On the screen it reads "X axis vibration detection failed" or "Y axis vibration detection failed"; in Fluidd it's "Failed to set ADXL345 register" and "invalid adxl345 id". The Max carries two accelerometers: the X one lives in the toolhead ribbon and adapter board, the Y one is a separate module under the bed (part B0N3B1).

1. Power down and reseat the toolhead ribbon, straightening bent pins with tweezers
2. Remove the bottom cover and reseat the Input shaper connector on the mainboard
3. Reseat the Y accelerometer cable under the bed
4. Reboot the printer after a firmware update — calibration legitimately fails without a restart
5. Compare mainboard and screen firmware against the pairing table and reflash both if they don't match
6. Still failing? Replace the toolhead ribbon (for X) or the B0N3B1 Y accelerometer module

23. Stock firmware is locked: no KAMP, no screws_tilt out of the box

There is Klipper on the Max, but it isn't your Klipper. Tom's Hardware puts it plainly: the machine doesn't run standard Klipper and can't be updated by the user from GitHub, so you're at the mercy of Elegoo's technicians for bug fixes. Neither SCREWS_TILT_CALCULATE nor KAMP is exposed in the interface — you add them to printer.cfg through the web interface at the printer's IP.

The alternative is OpenNept4une, an open build assembled from the original upstream projects. It's alive: 662 stars on GitHub, activity as recent as July 2026, release v0.1.7 from 22 November 2025 running Klipper 0.13. Stock screen support is still marked BETA. Owner reports split both ways — some say the printer has never run better, one had leveling fall apart and rolled back to stock.

1. Open the printer's IP in a browser (Settings → About Machine) — that's stock Fluidd, not a hack
2. Add a screws_tilt_adjust section with your bed screw coordinates to printer.cfg
3. Install KAMP or enable adaptive bed mesh in OrcaSlicer
4. Back up printer.cfg before every update — updates wipe your edits
5. If you want real Klipper, install OpenNept4une, but not the newest release: the community hit a bug that killed prints midway
6. For a dependable mesh on a 420×420 mm plate, owners add a Beacon3D or Cartographer probe

24. 500 mm/s on the box, 250 in the official FAQ, 16–25 mm³/s in reality

The box says 500 mm/s and 8,000 mm/s². The official FAQ for the same machine recommends around 250 mm/s, and separately caps PLA at 300 mm/s. The real ceiling isn't the motion system though, it's the hotend: measured flow lands around 25 mm³/s on PLA and about 20 mm³/s on some filaments.

An owner running two Maxes through 100 kg of PETG quotes an even more conservative number for the stock hotend — 16 mm³/s — and says a TriangleLab CHC XL swap pushed it to 30 mm³/s. Speed on a bedslinger with a 420×420 mm plate still runs into the mass of that bed: one reviewer measured up to 270 mm/s on Benchy walls.

1. Run 200–250 mm/s as your working speed, not the 500 on the box
2. Cap volumetric flow around 20–25 mm³/s with the stock hotend
3. Treat 8,000 mm/s² as a bench limit, not a working acceleration for big parts
4. Always run Input Shaper: without it high speed gives you ringing and skipped steps
5. If you genuinely need flow, fit a CHC-style hotend and recalibrate the flow from scratch

Neptune 4 Max error message reference

Klipper reports failures as plain-text messages rather than numeric codes, so you search by phrase. Below are the messages Elegoo officially documented for the Neptune 4 Max, with the cause and the first thing to try.

Common 3D printing problems

Beyond the Max-specific faults above you'll meet the usual FDM problems. They aren't unique to this printer, so each one has its own detailed guide:

• First layer won't stick or lifts — how to dial in the first layer
• Corners pulling off the plate — the warping guide
• Strings and whiskers between walls — how to eliminate stringing
• Clogged nozzle or stalled feeding — clogs and heat creep explained
• Shifted layers and ringing on walls — layer shifting and ghosting
• Walls too thin or too much plastic — under- and over-extrusion
• Filament popping and bubbling — how to dry filament properly
• Service schedule — 3D printer maintenance by calendar

Also worth reading: the OrcaSlicer guide — it's the easiest place to turn on adaptive mesh and Z-hop for the Max, remote access to your printer — Klipper on the Max exposes a web interface out of the box, and the best Neptune 4 mods, most of which fit the Max as well.

Elegoo Neptune 4 Max FAQ