Common UV Printer Error Messages & Warnings, Explained
CMBACRYLIC
UV Printing
UV Printing · Troubleshooting
Common UV printer error messages & warnings, explained
From a "Cover Open" warning that won't clear to prints that won't stop shifting — here's what's actually happening, and what to do about it, before you call support.
Warnings & errors
Print quality issues
Most first-time printer problems aren't actually mysterious — they're just unfamiliar. A warning pops up, or a print comes out wrong, and it's easy to assume something's seriously broken. Almost all of it comes down to a short list of known issues with known fixes.
Here's what to check before you pick up the phone, split into system warnings and print quality issues.
Warnings & errors
When the printer itself is complaining
Problem
"Cover Open" warning won't go away
The printer won't start a job because of a persistent "Cover Open" error, even though everything looks closed.
FixMake sure every cover and door is fully closed. Then check the red emergency stop buttons — if one's been pressed, gently pull it up until it clicks back into place.
Problem
Water Heater Lack / Error 705
A "Water Heater Lack" or "ERROR 705 WATER LACK" message means the cooling system is low on antifreeze solution.
FixRefill the system with the correct water-antifreeze mixture per your printer's operation manual. This keeps levels where they need to be and prevents the UV heads from overheating.
Problem
NCU Error
An NCU error means there's an issue with the Nozzle Check Unit — the sensor that detects missing nozzles and triggers recovery.
FixClean the NCU sensor if it's dirty with ink or debris. If the error keeps coming back after cleaning, the sensor's light source may have degraded and the unit will need to be replaced.
Print quality
When the print itself is the problem
Problem
Print is sticky after curing
Ink still feels tacky even after it's supposedly cured.
FixCheck your UV lamps and curing settings first. Avoid laying down overly thick ink — run fewer plates at once, or add a second pass or a higher curing setting.
Problem
Colors look dull or wrong
Colors come out muted, off-shade, or just don't match the design.
FixConfirm you're using the correct ICC profile. Enable a white underbase for dark or transparent materials, and compare CMYK against CMYK + White to see which one your job actually needs.
Problem
Print is shifted or looks doubled
The print looks like it's been duplicated or ghosted across the piece.
FixMake sure the material is firmly secured with tape or a jig. Recalibrate the table and double-check your origin settings — and avoid bumping the table mid-print.
Seeing lines or banding instead?
That's not on this list because it deserves its own breakdown — see our full guide on diagnosing deflection vs. missing nozzles vs. white ink issues to tell exactly which one you're looking at.
At a glance
Quick reference
| What you see | What's happening | What to do |
|---|---|---|
| "Cover Open" won't clear | A cover, door, or e-stop button isn't fully reset | Check covers/doors, reset e-stop buttons |
| Water Heater Lack / Error 705 | Cooling system low on antifreeze | Refill the water-antifreeze mixture |
| NCU Error | Nozzle Check Unit sensor is dirty or degraded | Clean the sensor; replace if it persists |
| Sticky after curing | UV settings or ink thickness issue | Check lamps/settings, reduce ink thickness |
| Dull or wrong colors | Wrong ICC profile or missing white underbase | Confirm profile, test white underbase |
| Shifted or doubled print | Material moved or table needs calibration | Secure material, recalibrate table |
None of these require guesswork once you know what you're looking at — a warning tells you exactly what system needs attention, and a print quality issue almost always traces back to settings, setup, or material. Save the service call for the ones that don't respond to these fixes.
Back to printing
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