We ran into a very strange issue with our Formlabs Form 4 today and are trying to understand what could have caused it.
We sent a relatively small print job to the printer with an estimated print time of around 1.5 hours.
When we checked after the expected completion time, we found that only the first few layers had printed and the rest of the model was simply missing.
We assumed it was a normal print failure and emptied the resin tank to remove the failed material. To our surprise, there was no failed print or cured resin in the tank at all. It appeared as though the printer had simply stopped exposing layers partway through the print.
Following Formlabs’ support article instructions, we added some resin back into the tank and ran the Clean Resin Tank function.
This is where things became stranger:
- Default 3.2 s exposure: no cleaning sheet formed.
- 6.4 s: no sheet.
- 20 s: still no sheet.
- Only at approximately 30 s exposure did a cleaning sheet finally form.
We removed the sheet, cleaned everything, switched the printer off and restarted it.
After restarting, we added some resin and tested the Clean Resin Tank function again at the default 3.2 s exposure. This time, it worked perfectly and produced a normal cleaning sheet.
We then filtered the resin, cleaned the tank, and restarted the same model in a different orientation.
Approximately 15 minutes into the print, the machine stopped with a “Debris Detected” warning.
When we opened the printer, instead of the model being printed, resin had cured across essentially the entire build-plate area, forming a large solid sheet.
While cleaning the tank afterward, we also observed a scratch/damage on the tank film.
We have now run Inspect Optics, and I am attaching the resulting images.
At this point, we are struggling to identify a consistent explanation for the sequence of events:
- The first print apparently stopped exposing after only a few layers, with no corresponding failed material in the tank.
- Tank cleaning initially required an abnormally long ~30 s exposure to produce a sheet.
- After restarting the printer, the normal 3.2 s tank-clean exposure worked again.
- The subsequent print then appears to have exposed approximately the entire printable area, rather than the geometry of the submitted model.
- The printer eventually stopped after detecting debris, and the tank film is now damaged.
NOTE - LPU and BLU was replaced by Formlabs in JUNE 2025 for similar issue as it was under warranty .
The new LPU has barely run for ~41000 layers.
