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Why does my printer add defects to my prints (nothing to do with slicer)? Answered

So I have a FDM 3D printer which I designed and built, it is very sturdy so I am sure that none of this is caused by flexing/resonances of the printer. My set up makes use of Repetier host and firmware, with cura being my preferred slicer. I have noticed that it has started to add strange details to my prints, both on corners and on rounded sides (see photos). These do not show up on the  slicer preview, and when i switch between slicers (cura and slic3r) they still remain. This has led me to believe that it may be a issue on the printer side. I have watched the printer as it prints and they are definitely being added on purpose by the machine (as in no flexing/resonance/lack of tension in the belts). this made me think it might be a firmware issue. It also does not go away if I slow down the printer. This has only happened recently, but  I can find no settings on the firmware that I have changed in this time period that would indicate something like this should happen. Just to be clear, in the photos, the near circular print should be perfectly circular, and the other print should have a perfectly square cross section. It also happens on both the models and the rafts/brims that I use. Any thoughts or ideas will be much appreciated.



Best Answer 4 years ago

You said it started, does that mean before it was printing fine?
If so I would first revert back to a working firmware to check if it is hardware or software.
Even with messed up steps the result should be evenly and not with added corners.
Since you tried on low speed as well I can rule out acceleration or belt problems as well.
And with different slicers showig the same problem IMHO it only leaves the firmware.

It looks like the print runs out of direction during a set of instructions and returns to the right position with the next set of instructions.
Might even be a communication problem, did you check the log for any problems of repeating errors?


Answer 4 years ago

Yes it was fine before, so I kinda thought it must have been a firmware issue. And I'm afraid I did not think to check the log specifically, though I do not remember any obvious errors showing up when ever I glanced at it.

Anyway, I did as you said, and got a new copy of firmware, put all the basic settings in. Now everything seems to print perfectly, done 3 prints so far and no obvious issues have presented themselves. So thank you very much for your help, slightly annoyed though that I couldn't pin point the cause.


Answer 4 years ago

I got my now totally outdated printer equipped with a Gen6 board and a locked firmware.
After flashing a bootloader to the board and configuring Marlin for it I know how you feel.
Sometimes you make a few changes over th time and all of a sudden nothing works as it should for no reason.
When I start tweaking on the firmware I first read out all the current Eprom values that I changed during use, like stepping, timings, pid settings and so on.
This way I know the basics are definately ok and can focus on other firmware settings.
If you have some digital calipers check the axes and extruder.
Where required tweak the setting until you got them spot on.
(Disabling the "prevent cold extrusion" in the firmware helps with the extruder as you can remove the hotend and just move the filament backand forth until the steps are fine.)
Doing these calibrations makes troubleshooting print issues later on much easier as you can limit it to slicing settings, mostly speed and extrusion settings.
You will know what that means once you have a bunch of different filaments and get sick and tired of messing with the extrusion multiplier to get it right ;)