# When dwelling G4, my printer is oozing, how can i stop that? [duplicate]

Here is the sequence of my Gcode, printed in mid-air:

Print (E20)
Retract (E-20)
Dwell (G4 10,000)
Move away (E0)
Print (E20)


See the path on the printscreen below:

When the printer dwells it oozes. How can i stop that?

I am using a WASP 3MT, pellet extrustion, 3mm nozzle, Marlin firmware, Gcode done on Silkworm for Grasshopper.

Gcode around the dwell:

G1 F300 X-25 Y-25 Z30 E15.96
G92 E0
G1  F0 X-25 Y-25 Z30
G1 F1000 X-25 Y-25 Z36 E-89.42
G92 E0
G4 P10000
G1  F0 X-25 Y-25 Z36
G1 F1000 X-25 Y-25 Z32 E0
G92 E0

• how much are you retracting? Bowden or direct drive? Would you show the full snippet of GCode, 3 lines before and after the G4? – Trish Nov 27 '18 at 19:37
• Are you using an all-metal hot end? – 0scar Nov 27 '18 at 20:05
• Instead of idling, have you considered printing a scrap part (like a wiper wall or cooling tower) in the corner? – Davo Nov 27 '18 at 21:05

## 3 Answers

Ooze is virtually unstoppable. This becomes apparent once you understand why an nozzle oozes. As the filament melts, its viscosity drops and the free flowing filament slowly makes it way out of the nozzle due to the action of gravity (and sometimes thermal expansion). If you make the throat air tight then you can use air pressure to keep the plastic from oozing out. Further you would have to immediately turn off the heat to the nozzle and cool the nozzle as fast as possible (possibly with a blower). Even if you retract the filament all the way out of the throat, there could still be some plastic left inside that will ooze out.

You retract the filament, yet you keep the heater on while the dwell. As you pull the filament back, you pull only the non-molten filament. The retaining molten filament follows gravity and sags down.

It is fixable to some degree though: Turn off the heat to let the filament cool before having the machine hibernate. That can reduce the amount of oozing, but not fully.

Since you retracted the filament (very far), but stay at elevated temperature for almost 2 minutes, this must be left-over residue inside the nozzle/throat that is stuck to the wall that becomes liquid and oozes out of the nozzle because gravity pulls it downwards.

This answer on the question "Ender 3 extrudes plastic whilst at standstill, and while moving to start of print" explains the oozing problem in detail.