Extruder oozes filament out and slides build platform on contact with nozzle tip

Question

If I am 3D printing on my Ender 3, and I pause the print, the extruder lets out more filament for like 2 seconds. This leaves a glob of dry filament on my print, which the could contact the nozzle tip, causing it to slide the build platform.

I have fixed the build platform sliding problem by attaching the included clips. However, another problem remains. Once the glob is made, the filament dropped on top of it gets pushed up, making the print not be even, which ruins the print. I don't think I did anything wrong on the setup, but it might just be that the extruder doesn't stop in time? Did I do anything wrong is is this an issue among all Ender 3s?

• I use the Creality Ender 3

Answer 1

I had this same issue, it's just how it works.

I solved it by pausing over infill, so when it resumes the blob is not visible. You can grab the filament with something as well, but it takes good timing. If you just pause/resume over infill then it doesn't matter.

Answer 2

It extrudes after a print to replace any filament that may have drooled out while it was paused.

Quite possibly it is extruding much more than necessary, and ideally, it would clean the nozzle after dong an extrusion like that. However, the stock ender3 doesn't support automatic nozzle cleaning, so that's not exactly an option.

Personally, I keep a long tweezers near the printer, and just grab the free space extrusion when it does this and clean the nozzle manually with the tweezers. It takes a little bit of care and speed to do this without causing other damage, however.

Answer 3

A hot nozzle will leak out material (called oozing) if the filament is not properly retracted or if pressure has build up in the path from the extruder up to the nozzle (typically in Bowden tube setup extrusion).

Pausing a print on an Ender 3 can be performed by two different methods, a manual pause invoked by the menu of the printer display, or, a G-code pause (note that the filament changing G-code is used instead of the dedicated filament pausing G-code M601 which is generally not supported).

In case of the latter option, a G-code (M600) can be used to pause and retract, use the same filament to continue, this way it is considered a pause.

A word of advice from All3DP.com's article "Ender 3 (V2/Pro/S1): How to Change Filament Mid-print":

The above script uses the M600 command to function, but this command may not be registered by your printer’s firmware. In our experience, the M600 command was successfully registered by the Ender 3’s original Creality (Marlin-based) firmware – indeed, according to Creality’s GitHub for Ender 3 firmware, the M600 command is programmed. However, if you have an older model of Ender 3, the feature may not have been activated in the firmware.

To prevent the blob you can use the answer provided by Kilisi of try to use the second method using G-code (if you know when you need to pause, e.g. to insert something into a print, your question doesn't state what the reason for the pause is).

Answer 4

Working pause-and-resume without damaging the quality of your print depends on the printer doing a lot to preserve the primed/ready-to-print state of the printer and avoid heat damage to the part you're printing and to the filament, and on your using very well-dried filament. If any of these requirements aren't met, you're going to have a bad day.

In particular, the printer needs to do extra retraction (at least an extra 10 mm, probably more like 20+) to get the filament completely out of the melt zone while paused, and needs to quickly move the nozzle away from the print so as not to melt it. If this is done right, unretracting by the same amount just when starting will get you back to the necesssary nozzle pressure to resume extrusion nearly uninterrupted. Marlin firmware can be configured to do this right, but I doubt it's done right in the version of the firmware shipped with your printer. You didn't describe what happens in detail when you pressed pause, but it sounds like this isn't happening, so it's likely doing just a "dumb pause" in-place.

If you really want good pause functionality, you probably need to investigate customizing the firmware. This is not terribly difficult, but also not dead simple, and can go badly wrong if you mess it up. You'd need to weigh these risks against how much you want the functionality.