Fine stringing during preheat after clearing clogged nozzle
Hello, all!
I recently switched to a 0.25mm nozzle and had no issues printing PLA with it for the first 3 prints. On the fourth, the nozzle clogged; the print was continuing but no filament came out.
I opened the extruder door and pulled the filament out with needle nose pliers. Now, however, I'm encountering very fine stringing as the printer preheats.
Prior to removing the clog, the filament would ooze out of the nozzle, but I could always grab and pull it away cleanly with needle nose pliers. Now, pulling it yields a very fine string, almost like a spider web, and that's before the calibration phase.
During the calibration phase, it is leaving filament at each of the points (see picture).
I've tried 3 cold pulls, reattaching the nozzle, and adjusting the idler screw so that the head of the screw is flush to the extruder. I'm not sure what else I could have done mechanically to change the behavior. I'm using the same temperature (Prusa defaults for PLA at 215C) that I've always used.
Any suggestions on what to try? Would a replacement hotend or another part solve my issue if I damaged something?
Thank you.
Best Answer by bobstro:
This is a fairly common occurrence with the Mk3. If your prints are otherwise fine, I wouldn't worry about damage. The easiest way to work around this and other stringing issues during startup is to use a 2-step warmup procedure for the filament. Roughly:
- Warm filament up to a temp that will not ooze, but will be soft enough to allow any pre-existing ooze to bend without damaging the bed during homing.
- Conduct mesh bed leveling with the filament still at the no-ooze temp.
- Upon completion of mesh bed leveling, complete nozzle heating to final print temp.
I've got a documented startup gcode example here that shows this plus several other startup housekeeping steps. Prusa recently implemented a 2-step procedure for the Mini but it has not made its way into the Mk3 startup sequence in the default profiles yet.
Environmental factors such as increased humidity might explain why you didn't encounter this previously. Filament will change characteristics slightly over time when exposed to varying environmental conditions. In any case, I wouldn't replace any hardware just yet.
RE: Fine stringing during preheat after clearing clogged nozzle
This is a fairly common occurrence with the Mk3. If your prints are otherwise fine, I wouldn't worry about damage. The easiest way to work around this and other stringing issues during startup is to use a 2-step warmup procedure for the filament. Roughly:
- Warm filament up to a temp that will not ooze, but will be soft enough to allow any pre-existing ooze to bend without damaging the bed during homing.
- Conduct mesh bed leveling with the filament still at the no-ooze temp.
- Upon completion of mesh bed leveling, complete nozzle heating to final print temp.
I've got a documented startup gcode example here that shows this plus several other startup housekeeping steps. Prusa recently implemented a 2-step procedure for the Mini but it has not made its way into the Mk3 startup sequence in the default profiles yet.
Environmental factors such as increased humidity might explain why you didn't encounter this previously. Filament will change characteristics slightly over time when exposed to varying environmental conditions. In any case, I wouldn't replace any hardware just yet.
RE: Fine stringing during preheat after clearing clogged nozzle
This is a fairly common occurrence with the Mk3. If your prints are otherwise fine, I wouldn't worry about damage. The easiest way to work around this and other stringing issues during startup is to use a 2-step warmup procedure for the filament. Roughly:
- Warm filament up to a temp that will not ooze, but will be soft enough to allow any pre-existing ooze to bend without damaging the bed during homing.
- Conduct mesh bed leveling with the filament still at the no-ooze temp.
- Upon completion of mesh bed leveling, complete nozzle heating to final print temp.
I've got a documented startup gcode example here that shows this plus several other startup housekeeping steps. Prusa recently implemented a 2-step procedure for the Mini but it has not made its way into the Mk3 startup sequence in the default profiles yet.
Environmental factors such as increased humidity might explain why you didn't encounter this previously. Filament will change characteristics slightly over time when exposed to varying environmental conditions. In any case, I wouldn't replace any hardware just yet.
This is something that should be offically included in PrusaSlicer
RE: Fine stringing during preheat after clearing clogged nozzle
This is something that should be offically included in PrusaSlicer
It is for the Mini. Not sure why the 2 step procedure hasn't been added to the Mk3 startup gcode, but easy enough to add it yourself.
RE: Fine stringing during preheat after clearing clogged nozzle
This is a fairly common occurrence with the Mk3. If your prints are otherwise fine, I wouldn't worry about damage. The easiest way to work around this and other stringing issues during startup is to use a 2-step warmup procedure for the filament. Roughly:
- Warm filament up to a temp that will not ooze, but will be soft enough to allow any pre-existing ooze to bend without damaging the bed during homing.
- Conduct mesh bed leveling with the filament still at the no-ooze temp.
- Upon completion of mesh bed leveling, complete nozzle heating to final print temp.
I've got a documented startup gcode example here that shows this plus several other startup housekeeping steps. Prusa recently implemented a 2-step procedure for the Mini but it has not made its way into the Mk3 startup sequence in the default profiles yet.
Environmental factors such as increased humidity might explain why you didn't encounter this previously. Filament will change characteristics slightly over time when exposed to varying environmental conditions. In any case, I wouldn't replace any hardware just yet.
This resolved my issue and got me back to printing! I'm a huge fan of the new startup code; there was absolutely no stringing or oozing during calibration.
A Benchy I printed had some "acceptable" levels of stringing, but I also never adjusted/lowered the print speed to compensate for the new 0.25mm nozzle. I'm still very impressed by the level of detail and can continue to troubleshoot
Thank you!
RE: Fine stringing during preheat after clearing clogged nozzle
Thanks for the code! Totally eliminated stringing. I had tried it with your live z square and it worked well. Just added to my printer's startup.
Zero initial stringing and oozing.