J1 slows down in big prints, failing prints after hours; fixable by power cutoff (video included)

I think there is a buffering problem in the firmware, this is how to reproduce:

**Video of the printer being fast on early layers (start.mp4), slow on late layers (end.mp4), and screenshot of slicer. You can also see the quality degradation of later layers, printing the exact same shape.


  • slice a very large file (I used prusa)
  • after 10-20 MB, the printer begins to stutter and make pauses, which leads to excessive filament buildup, that can look ugly or ruin the print
  • cut the power to the J1 and resume printing with failure-recovery
    → the printer is fast again!!

Not the problem

  • it is not the USB-Stick, I disconnected it; the printer prints from internal storage
  • it is not an issue with pauses in the gcode - it outputs the same pattern for every single layer, simple G-movements.
  • it is not a heat problem: I sliced the same shape with a different slicer to a smaller file of 7MB, and it printed flawlessly.

Likely the problem

  • some buffer/memory runs full in the printer, that makes it too slow to parse the gcode file on time, or some arraylist keeps growing, that is parsed on every gcode line, which eventually stalls the printer; however, on printer reset, the memory is freed, or the list is emptied, and it is fast again. Maybe its the whole data of the already printed part of the file that the printer keeps shuffling around in memory, although it doesn’t need it anymore.


  • the firmware should flash its memory or heavy data structures periodically, for example on layer change, so no hard reset would be needed.

I want to contact support soon, but want to ask you for similar experiences, or even solutions?

Hi, I have also just run into this problem. Mine occurred after the printer had been on for two or three days and I had run several large (file) prints through it. I stopped the print by turning off the machine and just went to bed and have now just started a new print (same file). Hoping it works better.

That said, I have started to notice a growing chance of errors happening with the printer. Still relatively reliable, but if I am running it non-stop for with several prints for a week or longer, I am bound to end up with some sort of usually small issue. This is the first time I’ve noticed the print was messed up.

What firmware are you running? I think mine is 2.5.11; I haven’t updated it since I got it in September.


I am running the latest 2.6.2 firmware. I am buffled about just how slow the printer gets midprint, indicating a deeper problem, since usually, the printer is really fast.

when you experience lag issues, can you try to cut the power and resume the print? Can you confirm it is fast again after that procedure?

I ran some more tests.

  1. I printed the same file again and ran into the same printer slowdown after 1 hour of printing again, I cut the power and resumed, and the print was smooth again, so it is wholly reproducible.

  2. I wrote a script that removes any comments (Lines that start with ; ) from the gcode file. It shrunk from 17MB to 13MB, and I lost the preview icon and all preview settings. However, I could print the same gcode without issues. Wow. Which leads me to the question: why does it take the J1 soooo long to skip commented lines? I guess it does something with the comments. Interpret them? Store them in memory? Collect them? Debug log them?

I hope some official staff from Snapmaker reads this and can have a look in the software. I can provide the gcode files if it helps. No way a one line comment of 15 characters every 10 lines is too much to handle for a Ghz-powered modern 3d printer.

I suggest to open a ticket or email support and send them the files and describe like here.
This will make your machine better if they catch the act :+1:.



Could your issue be linked to the one reported here?

Hi @xchrisd I would love to, but they require an order-id as a mandatory field, which I cannot provide, since it was a kickstarter purchase, I have no such number, and even though I own the printer, I cannot request support :frowning:

@obertini, yes, I think this can be linked. The file size is roughly the same and it is also a prusa sliced file with lots of comments.

I hope something will move; the latest repo update was 8 months ago. I was surprised to see that someone over there at snapmaker woke up and released a small update 4 days ago. I hope they return to a more “active” development cycle soon. Imagine buying a printer for 1000$ and then it cannot print large files reliably, reproducibly failing at high layers. Its a PR nightmare.

You could even email them.