How do I get rid of plastic dropping out of the nozzle?
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I've got an IDEX printer which works great but multicolor prints are usually a mess. I even have a purge bucket + wiper and after the purge & wipe process, the nozzle is clean but on the way from the bucket to the print object, about 5mm of plastic drop out of the nozzle which then protrude from the outer wall of the print object.
I already tried adjusting the retraction settings but they don't seem to change anything (which makes sense since retraction only pulls back the solid part of the filament and does not affect the already molten part in the nozzle very much).
The only solution I can think of is a prime tower (which I wanted to avoid, hence the purge bucket). Increasing the travel speed will probably minimize the leaking part too but not get rid of it 100%.
Has anyone solved this issue with his/her multi extruder printer?
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@techni Which hotend?
Best
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- Use the lowest possible temperature that you can get away with.
- Use the maximum amount of retraction you can get away with.
- Use the fastest non-print move speed you can.
All the above will help but you might struggle to eliminate 100% of all oozing. To mitigate, you can print infill before perimeters. Also PET-G is a lot less prone to oozing that PLA.
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@pcr Copperhead from Slice Engineering
@deckingman Thanks for the tips, I have only tried PLA so far at 185°C which imo is already quite low. -
Hot ends have holes that are larger than the filament diameter (to reduce push force required to move the filament?) which means they aren't sealed. That means that when the filament retracts, there's no suction created to pull the molten filament up in the nozzle.
If the hotend were sealed airtight, the retracting filament might behave more like a piston and reduce pressure in the heater block/nozzle. Maybe the viscosity of the molten plastic is too high to be sucked up by a small change in pressure. I think it's going to depend on the plastic being printed, the temperature, the diameter of the nozzle, and the length of retraction.
O-ring(s) could be put in the cold end of the hot-end (or at the cold side of the heatbreak) and would fit tightly around the filament. It would increase the drag on the extruder motor, but they seem to have plenty of push/pull capability, especially those with gear-reduced filament drive. The ring(s) would probably wear out with use and require periodic replacement.
Hmmmm....
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@techni said in How do I get rid of plastic dropping out of the nozzle?:
@pcr Copperhead from Slice Engineering
@deckingman Thanks for the tips, I have only tried PLA so far at 185°C which imo is already quite low.In that case, be very, very careful not to use too much retraction - especially with PLA. I know I said use the maximum retraction that you can get away with but with all metal hot ends, it is all too easy to pull molten filament up into the heat break where it will cool, solidify and cause a blockage.
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@mrehorstdmd said in How do I get rid of plastic dropping out of the nozzle?:
Hot ends have holes that are larger than the filament diameter (to reduce push force required to move the filament?) which means they aren't sealed. That means that when the filament retracts, there's no suction created to pull the molten filament up in the nozzle.
If the hotend were sealed airtight, the retracting filament might behave more like a piston and reduce pressure in the heater block/nozzle. Maybe the viscosity of the molten plastic is too high to be sucked up by a small change in pressure. I think it's going to depend on the plastic being printed, the temperature, the diameter of the nozzle, and the length of retraction.
O-ring(s) could be put in the cold end of the hot-end (or at the cold side of the heatbreak) and would fit tightly around the filament. It would increase the drag on the extruder motor, but they seem to have plenty of push/pull capability, especially those with gear-reduced filament drive. The ring(s) would probably wear out with use and require periodic replacement.
Hmmmm....
i tried putting o-ring on the cold end side . honestly , there was no difference .
I did not actually print like this , just tested the oozing amount , so maybe in actual printing it will have some effect .with idex printers , i think the best solution is to use silicone wiper under the nozzle just before the second head moves to print .so tool change macro should include purge - retract - wipe - print
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@hackinistrator said in How do I get rid of plastic dropping out of the nozzle?:
purge - retract - wipe - print
Well that's my current procedure. The problem is the step "wipe - print" where the head moves from the wiper to the print object. On the way there, plastic oozes out of the nozzle. I already tried changing the retraction in 0.5mm steps from 1 to 6mm (direct drive) with zero effect.
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@techni Try purge - wait a few seconds - retract - wipe. Use G4 Sn to wait. Alternatively, try purge - wait - retract - wait - wipe.
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@techni You have stated that you don't want to use a prime tower, but would you consider an ooze shield?
Depending on your slicer you can either generate an ooze shield or extend your skirt upward to keep it the same height as your object. If all your filament changes happen outside that perimeter the ooze will usually get scraped off by the ooze shield instead of sticking to your print.
Depending on your model geometry an ooze shield can represent a lot less plastic waste than a purge tower.
The IceSL slicer has a specific option to generate a close-contoured ooze shield which wastes as little plastic as possible while still being easily removed after the print finishes.
