Filament not extruding in bowden drive
March 05, 2015 09:23PM
I've tried converting my Prusa i3 rework from direct drive to bowden with e3d v6 hot end. I'm using this direct drive design and this e3d holder.
When (1.75mm ABS) filament is not inserted in the HE, it's moved fine by MK8 pulley thru the tubing. But as soon as I insert into hot end, it stops moving. What am I doing wrong? Could be because my PTFE tube is too long or something else? I'm new to this type of drive, so I'm in uncharted territory...
BTW, HE heats up fine, I'm able to push filament by hand and it's extruded.
Attachments:
open | download - bowden_issue.jpg (88.3 KB)
Re: Filament not extruding in bowden drive
March 06, 2015 11:30AM
From what I can see from the picture the length is fine, but you need to support the tube because those steep curves might cause problems, also a direct drive might be weak for your metal hotend.

Edited 1 time(s). Last edit at 03/06/2015 11:35AM by ggherbaz.
Re: Filament not extruding in bowden drive
March 06, 2015 01:24PM
Quote
ggherbaz
From what I can see from the picture the length is fine, but you need to support the tube because those steep curves might cause problems, also a direct drive might be weak for your metal hotend.
Thanks! I will try to add support and also tighten bearing so it pushes on filament harder. I know it worked for others with same hotened...
Re: Filament not extruding in bowden drive
March 06, 2015 04:39PM
If it works for others, then adjust the trim pot of the stepper driver so it supply more power to the motor and then play with the feedrate on the display.
Re: Filament not extruding in bowden drive
March 06, 2015 04:47PM
As ggherbaz wrote above, you may have to adjust the current supplied by the Pololu driver (I assume you are using a RAMPS controller) to the extruder stepper. This is explained very clearly in the wiki.

Also, make sure the fan that cools the E3D hotend is permanently spinning and cooling the hotend body. This is not a layer fan, so it should be connected to +12V and left on all the time the printer is working.
If the E3D hotend body warms up too much your filament will melt inside the hotend and jam it.
Re: Filament not extruding in bowden drive
March 06, 2015 05:14PM
Thanks guys, that's actually great idea. I will adjust stepper current and see if it helps. It was working fine with regular extruder, but I'm guessing bowden needs more power smiling smiley
Yes I'm using RAMPS 1.4. I have extruder set to 145 steps/mm. I didn't find calibration instructions for this type of extruder, so I assumed if it's similar to direct drive. With 145 steps when I extrude 10mm, exactly 10mm comes out from end of the PTFE tube.
Yes I have fan spinning when extruder is heated up, it's connected to D10. I'm using Repetier Host firmware, and it has setting for that specifically (I think they added it in v0.92). Fan stops spinning only when temperature goes below 30C.
Re: Filament not extruding in bowden drive
March 06, 2015 05:28PM
It also may be getting caught behind your hot end if it's not perfectly aligned. Remove the PTFE from behind the hot end and push some filament through. Back it out and try with a couple different pieces and see if it repeats. If your Bowden tube isn't properly seated in your connecter it may get caught in there too.
Re: Filament not extruding in bowden drive
March 06, 2015 05:29PM
I went through the same process, though I used my own extruder and hotend mount. The problem I had was that the filament hits the bowden cold end part on the edge when it comes out of the ptfe tube and the direct drive has trouble getting it over the threshold. I solved it by using a pencil sharpener on the filament. Works every time. Also resist the temptation of using the part of the filament that's already marked by the hobbed bolt, it will often be stripped when putting some force on it when it hits the hotend. Just cut it off, or at least 10cm so that when the filament hits the hotend the hobbed bolt has a solid piece of filament to grab on to.
Re: Filament not extruding in bowden drive
March 07, 2015 10:37PM
I've tried all suggestions, still no luck. I pretty sure it's something to do with the drive mechanism. It's just doesn't have enough power to push filament. It goes thru if I assist it with my hand, but nut on it's own. Gear just digs into filament. I'm giving up at this point. Going to switch to direct drive instead of bowden...
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