Fixing stringing on Prusa Mini
My 3D printer, Prusa Mini, needed configuration for the nozzle temperature, retraction length, and z-height. Otherwise, the printed material gets too stringy like the second picture on embedded link below.
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I made a short experiment for checking parameters.
| Case | Nozzle Temperature | Retraction length | z height | Memo |
|---|---|---|---|---|
| 1 | 200 ℃ | 3.2mm | -0.825mm | |
| 2 | 190 ℃ | 3.2mm | -0.825mm | |
| 3 | 180 ℃ | 3.2mm | -0.825mm | |
| 4 | 180 ℃ | 1.6mm | -0.875mm | Adopted! |
| 5 | 180 ℃ | 1.6mm | -0.825mm |
Test model
STL File: stringy_test_h12.stl
Assumption
- Printer
- Original Prusa Mini Kit, with Super PINDA sensor (= Prusa Mini+)(*1)
- Slicer software
- PrusaSlicer (ver2.4.2 on Slic3r).
- Filament
- RepRapper, REP-MPLA-1.75MM-1KG-WHITE
- PLA, 1.75MM, White
- Amazon.co.jp | RepRapper 1kg PLAプラス (PLA+) ホワイト 高強度PLAフィラメント 3Dプリンターフィラメント 1.75mm
- I did not so much care about the filament - I stored filament exposing the room air in humid Japanese spring. Too much moisture will cause bubbles and messy lines while printing. Drying the filament out might bring better printing quality.
Prusa configuration points
On Prusa slicer:
-
Nozzle temperature:
- Filament Settings > Filament > Temperature > Nozzle: Other layers
- Filament Settings > Filament > Temperature > Nozzle: Other layers
-
Retraction length:
- Printer Settings > Retraction > Length
- Printer Settings > Retraction > Length
-
Z height:
- Manually tweaking the gear on the Prusa Mini
Experiment results
Temperature
From a forum | Stringing! how to fix that?, lower temperature (200℃ than 215℃) solved it. As the default setting was 210℃, I differ the nozzle temperature except the first layers in 200℃, 190℃, and 180℃
Nozzle temperature > other layers:
| Case | Nozzle Temperature | Retraction length | z height | Memo |
|---|---|---|---|---|
| 1 | 200 ℃ | 3.2mm | -0.825mm | |
| 2 | 190 ℃ | 3.2mm | -0.825mm | |
| 3 | 180 ℃ | 3.2mm | -0.825mm |
Case 1-1: 200 ℃ (front)
Case 1-2: 200 ℃ (left)
Case 2-1: 190 ℃ (front)
Case 2-2: 190 ℃ (left)
Case 3-1: 180 ℃ (front)
Case 3-2: 180 ℃ (left)
I tried 3 different temperatures. However, the outcomes did not show significant difference. It can be said lower temperature would be better in terms of energetic efficiency?
Retraction length
Next, I tried to check the length of retraction. All above experiments are configured as retraction length: 3.2mm, I changed it into 1.6mm.
Printer Settings > Retraction > Length
Case 5-1: Retraction length 1.6mm (front)
Case 5-2: Retraction length 1.6mm (left)
The stringing are solved significantly by changing retraction length while some tiny string still remains.
z-axis height
I checked the extruder nozzle might physically touch to the filament and need calibration. All above experiments are based on z-height: -0.825mm and I changed it into -0.875mm
Case 4-1 : z-height -0.875mm (front)
Case 4-2 : z-height -0.875mm (left)
Change in the z-axis height seems to improve the print quality slightly.
To sum up, my final calibration for the printer with the filament is:
| Case | Nozzle Temperature | Retraction length | z height | Memo |
|---|---|---|---|---|
| 4 | 180 ℃ | 1.6mm | -0.875mm | Adopted! |
Note
(*1) The difference between Prusa and Prusa Mini+ (ref: Original Prusa MINI to MINI+ upgrade kit): Prusa Mini+ including:
- a Y bracket, which is easier on the assembly process for Prusa
- a Super PINDA sensor, which is a temperature-independent sensor that doesn’t require the use of a thermistor.