¶ Stringing Issue
Stringing issue is very common during 3D printing. We'll discuss it here and provide you some recommendations to avoid or relieve it.
¶ Factors
- Refer to figure - 1, during the printing process of the 4 lags of this blue chair, when the extrusion of a certain layer of one lag was finished, extrusion was stopped and nozzle was moved from position A to position B, then it started doing extrusion for the layer of another lag.
- The extrusion should be stopped as expected, since the feed motor stopped working during the nozzle movement from position A to B. However, the melt filament inside nozzle at this moment is somehow like a spring, there was still compression on the melt filament inside nozzle even though the feed motor had already stopped working, so filament came out of the nozzle until the compression of melt filament was relieved.
- Then, the melt filament came out of nozzle during the movement from position A to B was stringed (if temp of extruded filament cannot be lowered down quickly).
So, we can address 2 key words for the stringing issue - the compression and temp
¶ The compression
Extrusion doesn't start immediately together with the movement of feed gear. When the feed motor and gear starts feeding, the rigidity filament is forced to going forward in the throat, and it starts compressing the melt filament inside the nozzle, the gap between polymers becomes smaller and smaller, like the deformation of a spring, once the compression reaches a certain level, extrusion then starts. When the feed motor and gear stops working, there is still compression on the melt filament, and the compression is going to be relieved, the only way for relieving compression for melt filament is to come out of the nozzle, since there is rigid filament upon it in the throat.
So, how can we avoid or relieve the stringing issue?
- Retraction
| In slice software, we need to make the proper settings for the filament retraction to give the melt filament inside nozzle some space to relieve the compression. |
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- Dry the filament
Fully drying the filament improves the stringing issue, especially for the high water-absorbing material. When the filaments with high moisture come into the nozzle, the moisture will evaporate and generate air bubble, this makes the “spring” compressed even more, which then leads to worse stringing issue. More seriously, the large amount of overflow could be accumulated around the nozzle and finally wraps the hot-end and nozzle, damaging the parts and causing printing failure.
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¶ Printing Temp
The melt index (fluidity) and viscosity of melt filament depends on the nozzle temp that we set. We can lower the printing temp to break the stringing easily. But keep in mind that there are some negative effects like nozzle clogging issue or else.