Anycubic Photon Mono 4 Ultra Known Issues: 35 Real Faults and Fixes

The Anycubic Photon Mono 4 Ultra is a compact 2024 MSLA printer built around a 7-inch 10K mono LCD (9024×5120 px, 17 µm pixel), a 153.4×87×165 mm build volume, a COB light source with a Fresnel lens, and an ACF release film that pushes print speed to 120 mm/h on high-speed resin. The printing itself is genuinely good. What piles up around the printing is about three dozen model-specific gotchas that the manual either skips or, worse, documents for a different machine.

Everything below is specific to this model: the file format, two separate firmwares, false strain-gauge alarms, the argument about whether the ACF frame can be split, deeply recessed LCD screws, and a support wiki that keeps pointing at the wrong printer. Generic resin printing problems — elephant's foot, cupping blowouts, exposure tuning, supports — live in a separate article: 13 most common SLA and MSLA print failures.

1. The printer refuses your file: the Ultra uses .pm4u

You sliced the model, copied it to the USB drive, and the printer answers with "File format error!" or "Failed to open file!". Almost always the reason is the same: the Photon Mono 4 Ultra prints .pm4u files only. The base Photon Mono 4 uses .pm4n, the Photon Mono M7 uses .pm7, the M7 Pro uses .pwsz. They are not interchangeable even though they look identical on the drive.

The second trap is an outdated slicer. On the German drucktipps3d forum a Mono 4 Ultra owner reported that Anycubic Photon Workshop 3.1.4 saves slices as .pwma instead of .pm4u: "funktioniert, erstellt aber als slice-Dateien nur .pwma". Another owner on the same forum could not find the model in the slicer's printer list at all shortly after launch. Both cases were closed by a software update.

1. Update Anycubic Photon Workshop to 3.6.3 — you will need it for on-device exposure calibration anyway.
2. In the slicer open Machine → Add Printer and select Anycubic Photon Mono 4 Ultra, not Photon Mono 4.
3. Check the Sliced File Suffix field in machine settings: it must read pm4u.
4. Re-save and re-copy the file. Renaming an old slice with the wrong extension does nothing — the internal structure differs.
5. The printer cannot read .stl or .obj directly. Everything has to be sliced first.

2. USB drive not recognised: 64 GB in the manual, 32 GB in the wiki

The drive is in, but the screen shows neither its label nor any files. Anycubic contradicts itself here. The Ultra's own user manual and Quick Start Guide say: "ensure that the capacity of the USB flash drive is within 64G and the format supports FAT/FAT32". The USB troubleshooting page linked straight from the Ultra hub says the opposite: "The printer cannot read USB drives with a capacity of 32GB or higher".

1. Format the drive as FAT32 with a 4096-byte allocation unit.
2. Put the file in the root directory — the printer does not read inside folders.
3. Name files in plain English, no special characters, within 15 characters.
4. Save the slice to your desktop first, then copy it across. Saving straight onto the drive is the classic way to get a corrupted file.
5. Always eject the drive safely, otherwise you will meet "Failed to open file!" next time.

3. Photon Workshop: the file picker vanishes and supports need a manual pass

Fabbaloo, testing the Ultra in January 2025, hit a memorable bug in what was then the current Photon Workshop 3.5: "If you hit 'load', the file picker box would appear and instantly disappear. This happened on both Windows and Mac versions of the software". The workaround is trivial — drag models onto the build plate instead.

Two other complaints about the same slicer are still valid in 3.6.3. There is no auto-orientation at all, so every part gets rotated by hand. And auto-generated supports, much improved though they are, still miss spots: "It's best to manually inspect the supports at all times".

• File picker closing instantly — drag and drop the model onto the plate.
• After auto-supporting, walk the model visually: overhangs, thin features, isolated islands.
• Set orientation yourself — 20–30° off the plate beats flat almost every time.

4. Third-party slicers: vector format must be turned off

Anycubic's own product FAQ spells it out: "1. Adapt to the official slicing software, which supports vector slicing; 2. Compatible with Chitu, Tangoo and Lychee slicing software, slicing mode aligned with WorkShop, vector format turned off". Vector slicing lives in the native slicer only; in ChiTuBox, Tango and Lychee you must match the Workshop slicing mode and disable vector output.

There is no official PrusaSlicer profile either. On the Prusa forum an Ultra owner's question went unanswered by the vendor, and the profile mentioned in the UVtools changelog is generated by UVtools itself, not by Prusa or Anycubic.

5. UVtools: the print stalls on the last layer

The symptom is distinctive: the model prints all the way through, then the job hangs on the very last layer and you cannot tell whether it was exposed. The same file sent straight from the drive without UVtools processing finishes normally. Long jobs suffer more often than short ones. UVtools discussion #1049 was opened specifically about the Photon Mono 4 Ultra.

The cause is the per-layer settings flag UVtools writes into the file. The maintainer states the limit plainly: "Global parameters can be changed, but not per layers". That flag has been fighting Anycubic machines for a while.

1. Change parameters globally, never per layer — per-layer settings do not work on this printer.
2. If a file is already broken, hit Reset while holding SHIFT: that is a full rebuild, not just a value rollback.
3. Before saving, confirm the highlight field in the file is not set to True.
4. Keep the tool current: .pm4u support landed in UVtools 5.0.0 on 18/12/2024, and the project is alive — 6.2.1 as of August 2026.

6. There is no firmware to download: OTA is the only path

Want to update or roll back from a USB drive? There is nothing to download. On the wiki's local update page, where the firmware link should be, the text reads "Firmware download link: Please wait". On Anycubic's official firmware and software page the Photon Mono 4 Ultra entry contains only user manuals in eight languages and test files — no Firmware section at all. For contrast, the Photon Mono M5s Pro on that same page lists firmware v1.0.5.1.

1. Get the printer online: Settings → WLAN, 2.4 GHz only.
2. Confirm the cloud icon appears in the status bar.
3. Open Information → Versions → OTA upgrade and confirm.
4. When it finishes, press OK and let the machine restart.
5. Versions current at the time of writing: 4.0.7.7, 4.0.7.8 and 4.0.7.9. Anycubic publishes no release dates, only numbers.

It helps to know what the recent releases actually fixed. 4.0.7.7 closed a false "tension sensor missing" prompt after a factory reset, improved file storage across power loss and fixed preview progress during remote printing. 4.0.7.8 reworked low release force and the levelling routine. 4.0.7.9 repaired server switching — the very China/Global toggle that keeps the app from binding.

7. A second firmware: without the FPGA patch half the features never appear

A little-known detail: the Photon Mono 4 Ultra carries two independent firmwares. The main one arrives over OTA; the FPGA patch is flashed by hand from a USB drive. On 10 July 2025 Anycubic published a dedicated notice with the order of operations — OTA to 4.0.7.9 first, then manually flash FPGA_0918_0052.bin. Do only the first half and the promised on-device exposure calibration simply will not be there.

What the patch adds: an exposure test split into 4, 6 or 8 zones, one-click automatic placement, automatic zone numbering, and — the useful part — the ability to change exposure time per zone right on the printer without re-slicing. Photon Workshop 3.6.3 is required for it to sync.

1. Update over OTA to 4.0.7.9.
2. Download FPGA_0918_0052.bin from the firmware update log page on the Anycubic wiki.
3. Format a USB drive and keep only that file on it: "It is recommended to format the USB drive and only save the firmware files on it".
4. Insert the drive, open USB Flash drive Storage on the print page, find the FPGA file and start the upgrade.
5. Update Photon Workshop to 3.6.3 or the zone calibration will not sync with the slicer.

8. Wi-Fi is 2.4 GHz only, and the server may be set to China

The radio works exclusively on 2.4 GHz (2.400–2.4835 GHz) in AP, STA and AP+STA modes. If your router only broadcasts 5 GHz, the printer will never connect no matter how many times you retype the password. The second requirement is WPA-PSK or WPA2-PSK encryption.

The third and most frustrating reason is the server location. The official binding guide is explicit: "change the server location from 'China' to 'Global'". While it stays on China, a printer outside mainland China will not reach the cloud and the app will never see it.

1. Settings → WLAN → Server Location → choose Global.
2. Make sure the router broadcasts a separate 2.4 GHz SSID rather than 5 GHz only.
3. Check the encryption mode: WPA-PSK or WPA2-PSK.
4. Give it one to two minutes on the first connection — the printer is not instant.
5. When joining the printer's own hotspot your phone will honestly report "no internet". Choose to keep using that network and stop the phone from switching away. On Huawei devices also disable WiFi+.

9. No CN code means the printer cannot be bound to the app

Anycubic cloud binding runs on the device CN identifier: the app scans a QR code shown on the printer. Fabbaloo found the code would not work, and when trying to enter the identifier manually discovered the CN field was simply absent: "On this machine, there is NO CN NUMBER! That was the problem. I have no idea why this is the case". None of the cloud features could be tested as a result.

Two status quirks are worth knowing as well. If the app shows Busy on a finished job, restart the printer or start any print from the USB drive to clear the state. If it shows Offline, verify Wi-Fi is on and, if needed, remove the printer from the app and add it again.

10. "Residue detected" on a clean vat — on every single job

The most nagging fault on this machine. After the first successful print, every following job announces residue in the vat — with a visibly clean vat and a clean plate. Fabbaloo puts it bluntly: "every job after the first one would declare 'residue detected', falsely… I asked Anycubic about this, and they suggested I recalibrate the mechanicals through a super-secret menu option. I completed this calibration, but it didn't help".

The check is done by a strain gauge, not a camera. The manual states the threshold exactly: a solid residue counts as a piece at least 3 mm tall with a cross section of at least 9 mm². False alarms come from drifted mechanical calibration or a loose strain gauge connector.

1. Remove the plate, run Tools → Clear up for 10–30 s and lift the resulting sheet of cured resin with a plastic scraper.
2. Check the sensor: Tools → Other → Self-check → Force Detection. The icon should turn green.
3. Power the printer down, unscrew the adapter plate with an S2.0 hex key and reseat the strain gauge connector.
4. Run mechanical calibration: Settings → System → About → Detailed information, then tap the device name ten times in a row to reveal Mechanical Calibration.
5. In the calibration routine remove the plate and press "Removed", put it back and press "Installed", then confirm.
6. If nothing helps you can dismiss the prompt and keep printing — but you lose protection against real debris on the film along with the false alarms.

11. "Insufficient resin" and zero release force on a full vat

The same strain gauge also backs two other pre-print checks: whether there is enough resin for the job and whether the plate is installed. So the symptoms travel in a pack — "add resin" on a full vat, "printing platform is not installed" with the plate bolted on, zero release force. Anycubic's own calibration guide opens with exactly that: "When the material tank is insufficient, please add resin or the release force is zero. If the error prompt is repeatedly and the problem has not been solved…".

1. Reinstall the plate. If the prompt repeats, stop the job rather than forcing it through.
2. Run Tools → Other → Self-check → Force Detection.
3. Reseat the strain gauge connector on the adapter plate with an S2.0 hex key.
4. Run mechanical calibration through the hidden menu (ten taps on the device name).
5. Update to at least 4.0.7.7 — that release fixed the false "tension sensor missing" prompt after a factory reset.
6. If the gauge is genuinely dead, the assembly is replaceable: S2.5 and S3.0 hex keys, silicone sleeve off the Z cantilever. Anycubic sells it as S020274 for $23.99.

12. "Intelligent release" ships switched off

Before a job starts the printer shows a function selection screen. Two of them are enabled by default while "Intelligent release" is not — and hardly anyone notices. The manual describes it as: "The function can improve the printing success rate by optimizing algorithm. Enabling intelligent release while printing with the default resin_normal parameter group can also increase printing speed." And then: disabled by default.

• Failure detection — on. Watches for detachment and layer separation, pauses the job and shows a report. Bottom non-stick detection runs inside it.
• Off compensation — on. Needed on large-area layers where resin cannot flow back into the gap between model and film in time.
• Intelligent release — off. Turn it on: on the default resin parameter group it raises success rate and speeds the job up.
• Lift Z-axis to top — the plate parks at the top after printing, handy if you do not collect prints straight away.

13. There are no error codes: the printer shows a QR code

Owners coming from Bambu Lab or Creality expect to google an error code. That reflex fails here, and not because of bad search: this model has no numeric codes at all. The manual describes the mechanism: "When there is an error, the printer will pop up the error QR code. Please scan the code and follow the guide."

There is no pop-up reference page for the Ultra either — the only official table Anycubic published belongs to the base Photon Mono 4. The wording is the same on both machines; only the file extension differs, .pm4n versus .pm4u. We collected a combined table at the end of this article.

14. The Z axis whines and seizes: the nut wipes grease off the screw

First a thin whistle comes from the lead screw, then it turns into grinding, then the plate stops moving. The nasty part is that the printer never notices: it keeps counting layers while the plate sits still. An owner on r/AnycubicOfficial describes it precisely: "Prints fail about 15% into the print, while the printer keeps running like nothing is wrong, the print bed and Z-axis screw stay completely frozen in place. A loud struggling whine can be heard coming from the motor".

A commenter in a neighbouring thread explains the mechanism: "With use the nut can rub the grease off the screw, it will start whistling, then grinding". The nut gradually strips lubricant off the lead screw and dry friction takes over. Anycubic schedules screw maintenance roughly every three months — in practice nobody remembers until it starts singing.

1. Remove the cover, the resin vat and the build plate.
2. Wipe the screw dry with a lint-free cloth. A blackened screw after long use is normal and does not need replacing.
3. Apply a small amount of grease along the full height of the screw.
4. Tools → Z-axis → Z-axis zero point, then run the plate all the way up and back down in 10 mm steps so the grease spreads evenly.
5. Wipe off the excess, reassemble and run a short test print.
6. Repeat roughly every three months, or at the first odd noise.

15. The build plate freezes 4–5 minutes into the job

A rarer, separate scenario: the job starts fine, then four or five minutes in the plate stops moving and an odd noise appears. The owner who documented this replaced the strain gauge and the Z motor one after another with no effect: "The build plate stops moving at around 4~5 mins after a print job starts… I've replaced and tested force sensor, Z axis motor and none of them was the problem".

1. Rule out a dry lead screw first — cheapest and by far the most common (see the previous section).
2. Check the Z limit switch: it can stop motion too.
3. Power down and reseat the motor and strain gauge cables on the mainboard.
4. If every subassembly checks out, the mainboard is what remains. The wiki has a replacement guide, but inside the warranty period this is a job for support, not for your kitchen table.

16. The Z axis does not stop when homing

You press "Z-axis zero point" and the plate travels down without stopping. The culprit is the photoelectric limit switch or its harness. Anycubic publishes a dedicated guide for the Mono 4 Ultra on this one.

1. Power on and block the optical gate with a hex key — the indicator LED should light. If it does not, jump to step 3.
2. If it does light: remove the plate and vat, raise the axis halfway, press "Z-axis zero point" and block the switch. A healthy assembly stops the motor, lifts slightly and stops again.
3. Undo the limit switch mounting screw with an S2.5 hex key and reseat its harness.
4. Remove the mainboard cover with an S1.5 hex key and reseat the same harness on the board side.
5. Still failing? Replace the switch. Anycubic part number S020204, $18.99.

17. No adjustable feet, and the machine weighs 5 kg

The printer has no levelling feet — just two rubber rails underneath. Fabbaloo says it flatly: "it is impossible to level the Ultra: it does not have adjustable feet, just a couple of rubber rails". If your bench is not flat there is nothing to adjust: plate levelling squares the plate against the LCD, not the chassis against the floor.

The flip side of the same coin is mass: 5 kg at 231×236×430 mm. An elbow can move this printer, and a nudge mid-print tears the model off. The manual makes it a requirement: "Please place the 3D printer on a stable, level workbench".

18. The ACF film tears — and resin floods the electronics

The most expensive scenario on the list. The film splits, resin leaves the vat and goes into the chassis — onto the LCD, then under it, then onto the lens. An owner on r/resinprinting: "One day, i came back and noticed all the resin has leaked, and it turned out the film broke for some reason". The comments agree: "your printer is destroyed... you will have to open up the whole printer to see how much damage was caused".

1. Inspect the film before every print. The manual asks for the same: "Check the release film. If the film is broken, replace it immediately to avoid further damage to the 3D printer."
2. Never scrape cured resin with anything sharp — plastic scraper only, and only after the Clear up cycle.
3. Keep a fresh screen protector on the LCD: a five-pack costs $16.99, the panel costs $99.99.
4. If a leak already happened, power the printer down immediately and open the chassis. The longer resin sits inside, the more parts you replace.
5. After a leak, run an exposure test: dark patches and rings show whether resin reached the optics.

19. A dark ring in the exposure test: resin cured on the Fresnel lens

This one is specific to the Ultra's optics: a Fresnel lens sits between the COB emitter and the LCD. If resin seeps under the tape around the panel, it lands on the lens and cures there under UV. In an exposure test it looks like a dark doughnut — light will not pass even through a sheet of paper. The diagnosis from an experienced r/AnycubicPhoton member: "it's very likely that you spilled resin that got under that tape, under the lcd and onto the lens… the resin is now fused onto the lens and cannot be cleaned off".

Alcohol will not save it: the lens is optical plastic, and cured resin comes off only with the lens itself. The good news is that the part is cheap and replaceable independently of the panel.

1. Remove the vat and plate, lay an A4 sheet on the panel, open Tools → Exposure, pick an image and run it. Never look directly at the exposure — it is UV.
2. Compare the image on the control screen with the one on the LCD. If they match yet the dark ring persists, the panel is not the problem.
3. Peel the screen protector and repeat — a dried droplet on it is the most common cause.
4. Ring still there? Replace the Fresnel lens: S1.5 and S2.5 hex keys, 4 rear cover screws, 8 base screws, 12 screws on the lens itself.

20. A circle in the middle of the light field: the price of a single COB emitter

Instead of the usual LED array the Ultra uses one powerful COB emitter behind a Fresnel lens. Anycubic claims light uniformity of at least 90% and a beam angle of just 3°. In practice owners find a distinct circle in the middle of the field during exposure tests. A commenter with other MSLA and DLP machines is unambiguous: "Validation tests should produce uniform light… I guess at this point the short answer to your question is no, that is not normal".

Indirect confirmation comes from another thread in the same subreddit, where minis placed at the sides and rear of the plate printed cleanly while the ones nearer the centre and front failed twice. No review has published its own numeric uniformity measurement, so the claimed 90% remains unverified by anyone outside Anycubic.

1. Rule out dirt first: peel the screen protector, wipe the panel, inspect the lens (see the previous section).
2. Run an exposure test with a clean A4 sheet and photograph the result — you will need it for support.
3. Check that the panel ribbon cables are properly seated on the board.
4. If the ring survives on a new machine it is a warranty case. Anycubic asks for video rather than photos, so film the whole process from removing the vat to the result.

21. The LCD screws sit so deep that a normal hex key will not reach

The panel is a consumable and sooner or later gets replaced. That is when you discover the mounting screws are recessed absurdly deep. From r/anycubic: "The screws to release the screen are very very deep and I can't find a hex key long enough to reach them… at 102mm shank length, the one I got was 6" so ~123mm!". A 102 mm shank did not reach; only a 2.5 mm key around 123 mm long worked, and barely. The same owner's verdict: "Seems like either the designers didn't think or they actively made it difficult to replace the screen".

On price: the original panel is $99.99 from Anycubic (part S020275). The LCD warranty on the Mono 4 Ultra was extended from three to six months, but it does not cover resin leakage, damage to the scratch-resistant protective film, or impact damage.

22. The screen protector does not fit the frame

A small thing that grates. The protector lines up perfectly on three sides and misses on the fourth. An owner measured the mismatch at 0.01 to 3 mm and re-applied it six times with the same result. An English-language thread reports the same fault from the other direction — the supplied film is 0.5–1 mm larger than the panel, leaving bubbles along the edge.

Anycubic's own video adds to the confusion by demonstrating the procedure on a Photon Mono 4K using black tape that does not ship with the Ultra: "Anycubic video is not clear: they show a screen protector change on the Mono 4K which goes with some black tape (that they don't seem to provide)". Some owners cannot even tell whether a protector was fitted at the factory.

1. Wipe the panel and let it dry — dust under the film is worse than a misaligned edge.
2. Start from the side that lines up perfectly and push bubbles toward the opposite edge.
3. Do not trim the film to fit: a cut edge peels and resin gets underneath.
4. Replace it as soon as resin cures on it. The manual: "If there is resin being cured on the screen protector, please replace the protector immediately."

23. The ACF frame: 45,000 layers and the argument about splitting it

The manual states the film's life directly: "The film can be used to print 45000 layers." Curiously, Anycubic's generic cross-model wiki page gives a different figure — roughly 30,000 layers for ACF and NFEP against 10,000 for plain FEP. Trust your own model's manual, and track the real number with the printer's counter.

Then the argument starts. The Ultra's film comes in a quick-release frame, and some owners are convinced the two cannot be separated: "that printer uses a film that is already molded into the frame. There's no way you can split that frame to reuse it". Another Ultra owner in the same thread reported the opposite: "Use a thin blade to separate it, its just about patience really... Then I just placed the new ACF... Its been working fine since I did it, about 10 prints and counting". So the frame does split — it is a question of patience.

• The layer counter lives in Tools → Other → Print Layer. Reset it after a film change or the replacement prompt will never arrive on time.
• Official kits: 2 films for $21.00 (part S020267), 5 films for $39.99 (S020268).
• Frame teardown per Anycubic's guide: S2.5 and S3.0 hex keys, four diagonal screws first, then the remaining twelve steel ring screws, plus four vat positioning screws.
• Clean the vat before disassembly: Tools → Clear up, then wipe the film with alcohol and a lint-free cloth until an inverted vat stops dripping.
• Third-party vats such as Chitu and Hupat do not fit this printer — owners have checked.

24. ACF versus PFA: speed or fine detail

The stock ACF is a film built for speed. It lowers peel force and lets the factory parameter groups run fast. On fine detail it loses to PFA, and reviewers document that head to head by printing the same test on both films. The good news: the Ultra's vat shape matches the base Photon Mono 4, so a Mono 4 PFA film drops straight in — "Because the vat shape matches the Mono 4, one easy workaround is simply to use the Mono 4 PFA film".

• Printing full plates and valuing throughput — stay on ACF.
• Printing miniatures and busts where every fold matters — fit PFA and accept the speed loss.
• Run R_E_R_F after any film change: different transparency and different peel force mean the old exposure no longer applies.
• Do not fit an unbranded FEP cut to size. One owner did exactly that and started losing parts off the support tips, worst of all near the plate edges.

25. A plastic vat: no room for a heating belt

An owner planning to print through a cold winter asked the question directly and got an answer from Anycubic itself: "I heard from Anycubic directly and it's glass reinforced plastic". The Ultra's vat is glass-reinforced plastic, with metal only in the insert that holds the film. The familiar trick of wrapping a heating belt around a metal vat is off the table.

There is no vat heater by design either — the spec sheet lists "Dynamic Temperature Control Resin Vat: Not Supported". The manual's operating window is 8–40 °C at 20–50% humidity. Near the bottom of that range resin thickens, peel force climbs, and failures start exactly where everything printed fine in summer.

1. Heat the room or the cabinet the printer stands in, not the vat.
2. Let the resin bottle sit in a warm room before printing and shake it.
3. Keep the temperature in the upper half of the 8–40 °C window — around 25–30 °C resin behaves predictably.
4. Do not glue a heating belt onto a plastic vat.
5. If you regularly print somewhere cold, increase rest time before exposure and lower lift speed. That costs nothing and works.

26. The 48-hour rule and the vat cleaning cycle

Half the "mystery" failures on this machine start with a sheet of half-cured resin sitting on the vat floor after a previous failed print. It sabotages the next job and triggers the false residue alarm on top. Anycubic covers this with two simple rules.

1. After every failed print, remove the plate, open Tools → Clear up, set 10–30 s and run it. Then lift the resulting sheet with a plastic scraper.
2. Never scrape with anything sharp: "Do not use sharp objects to scrape the release film, in case the release film is damaged."
3. Not printing for more than 48 hours? Pour the resin out through the vat spout, filter it through a funnel and store it in a dark airtight container. The rule verbatim: "If you do not use the resin for over 48H, store it in an airtight container away from light."
4. A funnel model ships on the bundled USB drive — you can print your own.
5. Wipe resin stains off the vat straight away, not "later".

For washing, post-curing and storing finished parts see the dedicated guide: washing and curing resin prints.

27. Factory print parameters: three groups and what to change in them

Half the "what settings should I use" questions are answered by one table from the manual. Anycubic ships three ready groups, and the slicer names them exactly as the printer does.

• Groups ② and ③ are meant for models whose hollowed wall thickness is no more than 2 mm.
• Groups ② and ③ only work with the stock ACF film — Anycubic promises print failures otherwise.
• Group ③ applies to Anycubic high speed resin only. Standard resin will not survive those numbers.
• The figures come from Anycubic's own lab and are advisory: "The data above root in Anycubic lab, only for reference."

28. Parts bond to the build plate far too well

The flip side of generous factory settings: 30 seconds of bottom exposure is a lot for many resins. A reviewer summed it up as parts sticking to the plate so hard they would not come off cleanly. Attacking that with a metal scraper is a reliable way to either break the model or bend the plate.

1. Lower bottom exposure in 5-second steps: from the factory 30 s to 25 s, then 20 s. One owner settled on 20 s.
2. Do not touch normal exposure at the same time or you will not know which change did what.
3. Verify with an R_E_R_F print rather than by eyeballing a single model.
4. The mechanical answer is a flexible magnetic steel sheet: the part bends off with the plate.

29. The model does not stick, or parts tear off the supports

The classic picture: bare supports on the plate and the model itself lying on the vat floor as a sheet of cured resin. Anycubic prescribes a strict order — exposure, resin parameters, levelling, mechanical calibration. The order matters: tweaking exposure on a badly levelled plate is wasted effort.

1. Exposure. Remove the vat and plate, lay an A4 sheet on the panel, open Tools → Exposure, pick an image and run it. The control screen and the LCD must show the same image.
2. Resin. Print R_E_R_F and read the best exposure off the result. The filename cannot be changed — the printer recognises that exact name and nothing else.
3. Levelling. The paper goes on the LCD, not on the plate. Correct calibration means "there is a significant resistance or it cannot be pulled out". Check the left and right sides.
4. On the first descent the plate goes all the way down, lifts slightly and descends again — do not touch the paper during that.
5. Mechanics. Run mechanical calibration from the hidden menu (ten taps on the device name).
6. If only the model base sticks, raise normal exposure. If nothing sticks at all, raise bottom exposure.
7. Too little contact area — add a raft. The manual says exactly that: "Contact area between the model and platform is small. Please add a raft."

30. Anti-aliasing: factory level 1 instead of 16

Owners regularly ask whether the Mono 4 Ultra has real anti-aliasing, and even sellers fail to answer. The answer sits in the manual, in a note under the parameter table: anti-aliasing is set in the slicer, and all three factory groups ship at level 1. For precision work Anycubic recommends something else entirely: "If the print object needs high accuracy, please use group ① and modify the anti-alias level as 16 and the image blur as 3".

• Use group ①: 0.05 mm layer, 2.6 s normal exposure, 30 s bottom exposure.
• In Photon Workshop raise anti-alias level to 16 and image blur to 3.
• Expect noticeably longer prints: group ① is already the slowest of the three.

31. A cloudy lid, a glary screen and a laggy touch panel

Three small things that never break a print but wear on you daily. The Ultra's lid is translucent grey rather than clear amber, and you can barely see what is happening inside: "I found this quite difficult to see through… It gets even more opaque if you shine a light on it". The 4.3-inch screen is glossy enough to fight you: "the screen can be hard to read. Its surface is highly reflective". And reviewers note a small but noticeable lag when entering values on the touch panel.

Reviewers also record that the lid play on the Ultra is the same as on the base Mono 4, that resin droplets collect on the inside of the lid — "the lid will collect resin drips on the inside" — and that condensation forms under the cover in some climates.

• Watch jobs through the app rather than through the lid — you also get failure notifications that way.
• Turn the printer so no window or lamp shines directly onto the screen.
• Wipe the inside of the lid regularly: droplets cured by UV leave it permanently cloudy.
• Keep the machine away from fluorescent and UV lamps — stray UV cures resin in the vat.

32. No air purifier and no camera in the box

The AirPure 2.0 activated carbon purifier is an optional accessory for the Ultra — it does not ship in the box. There is no camera at all: remotely you get a text status in the app and nothing else. On top of that there is no automatic resin feeding — the spec sheet lists "Resin Auto-fill Unit: Not Supported".

For resin fumes, real exposure limits and how to arrange extraction in a living space we have a separate deep dive: 3D printing fumes and ventilation.

33. Half of the official documentation is written about a different printer

This is not nitpicking, it is a genuine source of mistakes. From the Photon Mono 4 Ultra hub on the Anycubic wiki, the links for FAQ, "model non-stick printing platform", maintenance and USB recognition all lead to base Photon Mono 4 pages. The networking page advises you to "reset the WiFi on the Photon Mono M5s printer". The Quick Start Guide sends you to the M7 Max binding guide. The ACF film replacement guide opens in Chinese.

Here are the numbers from those pages that you must not trust if you own an Ultra:

The manual itself exists in three versions at once: v0.0.2 for every language on the firmware page, while the wiki hub carries v0.0.3 in English and v0.0.4 for the other locales. Different translations of the same document even disagree on whether the 4.3-inch panel is capacitive or resistive.

34. Early batch lottery: half a lit screen, dropped exposure, a leaking gasket

Build quality varies, and it is worth planning for. An owner on r/anycubic documented a unit that went through every failure in sequence: "right from the start, the unit was shipped with only half of the screen area illuminated… Replaced the ribbon cable today, and again no output". First half the panel lit, then exposure dropped out mid-job, then the vat gasket leaked, and after a film change the projection disappeared entirely while the UV source still worked. Neither an LED module swap nor a ribbon cable swap fixed it.

That is one case, but a telling one: each of those symptoms also shows up separately in other threads. What matters is reacting immediately, while the 14-day no-reason return and 30-day after-sales guarantee are still live.

1. In the first days run an exposure test with an A4 sheet on the panel: Tools → Exposure.
2. Print R_E_R_F — it shows both field uniformity and whether the exposure is sane.
3. Film any defect on video: Anycubic support asks for video, and photo-only tickets drag on.
4. Keep the receipt. Without proof of purchase there is no warranty.

35. Warranty and spare parts: terms, part numbers and prices

Anycubic's warranty is not a single term — every subassembly has its own, and it pays to know that before something breaks.

Original spare part prices in the Anycubic store at the time of writing: ACF film $21.00 for two (S020267) and $39.99 for five (S020268), LCD panel $99.99 (S020275), resin vat with film $29.99 (S020269), build plate $25.00 (S020262), Fresnel lens $13.99 (S020265), strain gauge $23.99 (S020274), screen protector $16.99 for five (S020273), limit switch $18.99 (S020204). The printer itself lists at $344 in Anycubic's own store, and third-party marketplaces run well below that.

Photon Mono 4 Ultra error message reference

This model has no numeric error codes — only text pop-ups and a QR code. Anycubic published the verbatim wording on the base Photon Mono 4 page; on the Ultra the messages are the same and only the file extension differs. Below they are combined with the pre-print check messages documented in the Ultra manual.

Generic resin printing problems

Beyond the Photon Mono 4 Ultra quirks above you will meet the standard resin printing troubles — they are the same on any MSLA machine. We covered each one in a dedicated article:

• Elephant's foot, prints sticking to the film, cupping blowouts, exposure tuning and film tension — 13 most common SLA and MSLA print failures.
• First run, choosing a resin, safety gear and what you actually need to start — resin 3D printing for beginners.
• How standard, water-washable, ABS-like and high-speed resins differ — guide to 13 Anycubic resins.
• Washing, post-curing and storing finished parts — washing and curing resin prints.
• Sanding, priming and painting — post-processing 3D prints.
• Smell, extraction and safety in a living room — 3D printing fumes and ventilation.
• A regular maintenance schedule — 3D printer maintenance guide.
• What a single print really costs — 3D printing cost calculation.

Related reading: known issues of the base Photon Mono 4 — a different set of faults and a different file format, Photon Mono 4 vs Photon Mono M7, Photon Mono M7 known issues, and Elegoo Mars 5 Ultra known issues — the main rival in this class.

FAQ