Periodically inconsistent extrusion / Cyclic under extrusion
Hi Community,I have a very persistent problem with Inconsistent Extrusion.The error is most likely related to the amount of filament extruded and the extruder rotation, not to time, temperature control or X/Y movement.
The extrusion errors always occur after a certain amount of filament has been extruded and are independent of the print speed.
- The error occurs at regular intervals.
- The interval is constant.
- The interval remains the same even when the print speed is changed.
I think is very likely that there is a mechanical or feed-related periodic error, however I checked the extruder (driver gear and driven gear) multiple times and cleaned it although it looked totally fine.
I can't imagen that the hotend, PTFE, temperature, slicer, etc. produce precisely periodic errors, so I would rule these out as sources of the error.
987uzdefry Additional Info:
- Printer: Prusa Mini+ (tried with and without case)
- Filament: Polyterra PLA (Polymaker) and PETG Polymaker
- Nozzle: Tried both the original 0.4 and the E3D V6 Plated Copper 0.6 mm (problem occures with both nozzles)
- Bed Temperature PLA: 60 Celcius
- Prusa Slicer
- Print Speed: tried 15, 30 and 45 mm/s (First Layer Speed because it's only a single layer print)
- Retraction settings: (Prusa PLA standard)
- Length: 2.5 mm
- Speed: 70 mm/s
I tried a lot of different Slicer settings, but they had little to no effect, so I decided to continue the rest of the testing with the standard prusa slicer "0.20 mm STRUCTUAL" settings with the 0.4 Nozzle
I already tried a lot of different things:
- Bondtech gear cleaned → minimal contamination
- Idler screw adjusted
- Z-axis lead screw cleaned and lubricated → no improvement
- Drive gear visually inspected → appears to be in good condition
- PTFE insert in the hotend inspected → looks good
- No filament buildup in the hotend
- Cold pull performed multiple times → no improvement
- Tested multiple filament spools
- Tested different print parameters
- Changed extrusion multiplier → no improvement
- Reduced print speed → no change
- Increased temperature → errors become a little less severe, but remain present
Really hope you can help💫
Let me know if I should provide any additional info.
RE: Periodically inconsistent extrusion / Cyclic under extrusion
1. check if the filament moves smoothly when it is pulled from the spool - maybe the spool rotation has too much friction?
2. check long PTFE between the extruder and the print head, it's probably worn out badly - see the sticky post for more detail.
See my GitHub and printables.com for some 3d stuff that you may like.
RE: Periodically inconsistent extrusion / Cyclic under extrusion
Thank you for your reply!
1. The filament moves smoothly, I checked that multiple times.
2. The Bowden Tube is in decent condition. Also I cant't imagine how that could cause such an under extrusion with such a regular frequency.
RE: Periodically inconsistent extrusion / Cyclic under extrusion
If the bowden tube is worn out especially in the middle ( hard to see it) then it creates a cavity to which the filament clings or is trapped, if the force is enough then it gets released. Similar thing happen if the filament is sticky, some PLA unfortunately can get nasty in certain conditions.
You could try to see how the filament is placed in the tube ( use black filament).
The wear out usually gets much faster due to using abrasive filaments such as glow in the dark, or filled with carbon fiber or glass fiber, or some glitter infills.
Other ideas - damaged gears in the extruder or misbehaving extruder due to interference across the cables ( especially if they are not twisted enough) or damaged extruder motor.
See my GitHub and printables.com for some 3d stuff that you may like.