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Filament stuck in hotend after first print - unable to cleanly start more prints

Posted by leif 
Filament stuck in hotend after first print - unable to cleanly start more prints
December 08, 2017 08:30AM
Hi all,
I am pretty new to 3d printing here, so please close window before you get anoyed or ask me to search wiki smiling smiley


Note: Over the last year, I have built myself a delta mini kossel based mostly off DC42 design of the large delta built. Its got an E3D v6 hotend with smarteffector and a duet wifi controller. I have E3D PLA using it on 220deg C.

The printer calibrates well, but now starting to print my issue is really that the filament gets stuck in the hotend between prints and I am unable to cleanly start more prints

I have loaded filament manually at 220 after homing and calibrating bed. I run out 10-20mm and then start print. After print is finished, I stop printer and it cools down. My question is, should I really after print run filament out again 10-20 and pull it quickly out manually to have it ready before cooldown?

I read somewhere that people just let the printer cool down and start next print later on, which is what I have been trying to do. However, this is not working well for me. Filament is stuck and I then need to clean out nozzle and heatbreak, which I did by torch initially .. which is possibly exessive and should probably not be done this way smiling smiley :/ well, I learn many things lately.

Question is really, how do you guys manage the filament and printer between prints? I usually get 1-2 hour of playtime before evening and then proceed next day. So I would like to have printer in shape to start printing again next day when next print is planned.


Leif

Edited 1 time(s). Last edit at 12/08/2017 10:14AM by leif.
Re: Filament stuck in hotend after first print - unable to cleanly start more prints
December 08, 2017 10:23AM
First of all, do you have the E3D fan running continuously while the printer is on? It needs to run constantly to keep the heatsink cool - the only bit that should be hot is everything below the heat break. This keeps the plastic below the heat break molten, and unmelted above it.

Apart from that - I take the filament out when I've finished printing, then let the fan cool the hotend down to room temperature before I switch off the printer. Sometimes I leave the filament in, but I always make sure that the temperature is at room temperature before turning off, otherwise the heat will soak up to the parts of the hotend that are meant to be cool and solidify where it shouldn't.

Edited 1 time(s). Last edit at 12/08/2017 10:26AM by David J.
Re: Filament stuck in hotend after first print - unable to cleanly start more prints
December 08, 2017 10:27AM
It would be best to find the cause for the clogging. I suspect there is a gap between nozzle throat and heat barrier? The filament would fill this gap, cools down and blocks the hotend next time. Or maybe there is no PTFE tube inside the heat barrier?

If there is no mechanical reason, just retract filament a few mm at the end of a print. Also unretract the same amount in the beginning of a print. Use the start/end-gcode of your slicer for that.

;end code:
...
G92 E0
G1 F100 E-5
G92 E0
...
Re: Filament stuck in hotend after first print - unable to cleanly start more prints
December 08, 2017 12:27PM
As DavidJ pointed out 2 posts ago, it is very important to keep the hot end heatsink fan running until the extruder is cool enough. I wait until the extruder temperature is below 45C before I turn the printer off.

Also, if you are using an E3Dv6 or other all-metal hot end, don't retract too much filament in your slicer ending script.


Delta printer calibration calculator, mini IR Z probe, and colour touch screen control panel: [escher3d.com]

Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
Re: Filament stuck in hotend after first print - unable to cleanly start more prints
December 08, 2017 03:42PM
Thanks for all the great answers,
Firstly, I have been reassembling the hotend tonight and think I have idea as was pointed out by o_lampe. I have never hot-tightened the nozzle and so perhaps a gap has caused the filament to get stuck here. Also, not having waited until low degree before turning off. I have just set up machine again tonight and so will run a few tests to check if I have improvement. During reassembly I changed the heatbreak to a titanium one and also set up a lower tollerance ptfe tube from E3D.

Lastly I might ask for help later on how best to secure my hotbed to the lower frame as currently it is a bit "taped in place" smiling smiley See current setup in image below :p



Edited 2 time(s). Last edit at 12/08/2017 05:08PM by leif.
Attachments:
open | download - IMG_4755.jpg (169.3 KB)
Re: Filament stuck in hotend after first print - unable to cleanly start more prints
December 09, 2017 02:38AM
It hasn't been a subject yet, but the position of the Titan extruder could be improved by placing it in half height to one of the towers. Bowden tube length matters!
Re: Filament stuck in hotend after first print - unable to cleanly start more prints
December 09, 2017 04:57PM
Always hot tighten the nozzle to the heatbreak as hot as your setup allows I do mine at 270 deg C. Heatproof gloves help. I also put heatsink compound between heatbreak and heatsink, nothing between heatbreak and heater block, and copper grease between the nozzle and heater block.

As for bed mounting if it has holes i the aluminium bolt it directly to the frame with t nuts as one option. I designed these mounts
[forums.reprap.org] for my kossel Xl which you could adapt to your setup they're in my listing for the printer on thingiverse, they're quite stable, add a little cork insulation between them and the bed. [www.thingiverse.com]


Simon.

[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters. PT1000 cartridge sensors plug straight into duet boards and others.
Published:Inventions
Re: Filament stuck in hotend after first print - unable to cleanly start more prints
December 09, 2017 05:00PM
Quote
o_lampe
It hasn't been a subject yet, but the position of the Titan extruder could be improved by placing it in half height to one of the towers. Bowden tube length matters!

Place it on a swivelling bracket and you can reduce your bowden tube to much shorter, remember the detrimental effect of bowden tubes increases non linearly with length so every centimetre you remove has a big effect.


Simon.

[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters. PT1000 cartridge sensors plug straight into duet boards and others.
Published:Inventions
Re: Filament stuck in hotend after first print - unable to cleanly start more prints (SOLVED)
December 12, 2017 06:46AM
Thank you all for the great comments smiling smiley The extruder is now working great and I have printed out a few parts (low poly picachu smiling smiley and a pendant from Harry Potter over the weekend(I am trying to have my daughter of 11 to be more insterested in STEAM subjects and 3d printing and Lego robots would be a great start of this perhaps).

For the solution, I think a combination of securing the nozzle properly and having the right technique with pulling out filament and waiting to turn off the printer until proper temperature was reach solved it all completely.

I have also shortened the bowden tube by around 5cm, however to move it midway as suggested, I have not been able to find a suitable swivelling bracket for the extruder. @DJDemonD I did find the bracket from @dc42 (https://www.thingiverse.com/thing:2464289) which I will print to place extruder even closer, however it is not swivelling as suggested and perhaps I can remix it or if anyone have an idea for design which could work well for a 2020 extrusion for the titan I would be most gratefull smiling smiley
I've done a swivelling extruder by making a small piece which fits across the face of the titan extruder and is secured with two of the four screws that hold the titan together, the unit then lies on its side with the bowden tube emerging perpendicular to the delta towers. This bracket is attached with a keyring clip to a metal angle bracket which is fixed to a 3d printed hinge and then to one of the towers. This allows the hotend to swivel about as required, its only a proof of concept for now. There are more sophisticated swivelling/pivoting designs but not many that are shared.

[forums.reprap.org]


Simon.

[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters. PT1000 cartridge sensors plug straight into duet boards and others.
Published:Inventions
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