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Extruder problems

Posted by yiancar 
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yiancar
Extruder problems
June 01, 2015 08:48AM
Hello everyone,

I just finished assembly and the problem is that i cant extrude without giving some push to the filament.

the temperature of the extruder is correct( measured with a thermocouple) however the hobbed part of the bolt is a few mm of centre of the incoming filament. if i remove the extruder head the bolt manages to pass the filament to the other side but not easily. in addition my nozzle is 0.3mm.

Maybe the fact that the nozzle is to small and the fact that there is not enought torque due to the of centred bolt is the problem?


any ideas?
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nophead
Re: Extruder problems
June 01, 2015 11:14AM
Well 0.3mm will need a lot more force than the standard 0.4mm because it is an inverse fourth power law. You won't be able to to extrude as fast but it should work.

The bolt should be hobbed 25mm from the head and be centred exactly with the 6mm spacer. If not you could adjust the spacer by replacing it with M8 washers but you might need to invert the small gear if it is too close. The downside of that is you can't easily remove the hobbed bolt for cleaning if you have a filament jam.

[www.hydraraptor.blogspot.com]
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yiancar
Re: Extruder problems
June 01, 2015 01:50PM
Thank you, I'll have a look. also the fliament needs a lot of fiddling to go straight into the extruder, 99% i need to take the pushing bearing block out and guide it manually.

is this normal?
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nophead
Re: Extruder problems
June 01, 2015 04:14PM
No I simply load filament by turning the motors off and pressing it into the extruder while winding the big gear by hand. It should just grab the filament and load it.

Are you using 3mm filament?

Perhaps your springs are too tight?

[www.hydraraptor.blogspot.com]
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yiancar
Re: Extruder problems
June 01, 2015 04:52PM
no 1.75 the problem is that the filament does not go straight after the hobbed part, indication that its not centerred maybe?
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nophead
Re: Extruder problems
June 01, 2015 07:33PM
If you are using the standard Mendel90 extruder it only works with 3mm filament.

[www.hydraraptor.blogspot.com]
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yiancar
Re: Extruder problems
June 02, 2015 05:37AM
ups stupid me... I imagine I can change it in the config and reprint the extruder right?
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nophead
Re: Extruder problems
June 02, 2015 09:32AM
It might work or it might not close far enough, depending on the hobbed bolt. However you don't want a geared extruder for 1.75mm filament as you want to drive it 3 times faster with 1/3 of the force. Having it geared will limit your retract speed.

[www.hydraraptor.blogspot.com]
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yiancar
Re: Extruder problems
June 02, 2015 04:48PM
what do you suggest then?smiling smiley

any tried design?
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nophead
Re: Extruder problems
June 02, 2015 05:19PM
There are lots of designs about but I don't know if any are an exact fit for Mendel90. The two M4 holes 50mm apart used to be a reprap standard but not so much nowadays.

[www.hydraraptor.blogspot.com]
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yiancar
Re: Extruder problems
June 02, 2015 05:33PM
Thank you, Ill have a look, are there any known problems with using a bowden extruder?

I am just thinking that it would be much easier to implement one, and in the future upgrade to a dual setup
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nophead
Re: Extruder problems
June 02, 2015 08:01PM
I have never tried Bowden myself. I think there are problems with repeated retractions grinding down the filament. Cura likes to miss out retractions where possible because it is designed for a Bowden machine, whereas I prefer to always retract even when moving within an island or just a short distance.

[www.hydraraptor.blogspot.com]
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neildarlow
Re: Extruder problems
June 03, 2015 05:18AM
@yiancar The simplest solution is to use the recommended diameter filament.

I recently worked with someone who switched a Prusa i3 from a direct drive to Bowden extruder and he had so many problems he was forced to revert. The cost of buying new filament is less than the time wasted in correcting such an occurence.

Regards,
Neil Darlow

Edited 1 time(s). Last edit at 06/03/2015 05:19AM by neildarlow.

I try to write with consideration for all nationalities. Please let me know if something is unclear.
Printing with Mendel90 from fedora 25 using Cura, FreeCAD, MeshLab, OpenSCAD, Skeinforge and Slic3r tools.
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ideaHex
Re: Extruder problems
June 03, 2015 06:16AM
1.75mm filament seems to be a lot easier to come by in Australia. I use a jonaskuehling_gregs-wade-v3 (http://www.thingiverse.com/thing:18379) (mirrored) that I modified to accept 1.75 mm Filament and it works fine. I changed the following variables; filament_feed_hole_d = 2.25; and
filament_diameter = 1.75; in the scad file. I also had to grind flats on the idler bearing shaft to allow a little more clearance between the bearings so the extruder could grip the filament. It may not be the fastest printer but so far so good.
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yiancar
Re: Extruder problems
June 03, 2015 12:36PM
Quote
neildarlow
@yiancar The simplest solution is to use the recommended diameter filament.

I recently worked with someone who switched a Prusa i3 from a direct drive to Bowden extruder and he had so many problems he was forced to revert. The cost of buying new filament is less than the time wasted in correcting such an occurence.

Regards,
Neil Darlow

Thank you for the feedback, I am going to give it a try anyway as i dont see any other way to squeeze 2 hotends any other way in the future, except if there is a technic i am not aware about ?smiling smiley
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juanej
Re: Extruder problems
June 13, 2015 05:53AM
is there any other solution to this? I bought a E3D v6 lite for my nophead's mendel90 and now I'm back to the J-Head which is not working as good as it used to.
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hsbontop
Re: Extruder problems
June 13, 2015 04:31PM
Configured nophead's scad to work with 1.75mm and switched to a 1:1.2 gearing for additional speed. Currently using e3dv6 with great results. Scad/stl can be posted on thingiverse.
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juanej
Re: Extruder problems
June 13, 2015 05:11PM
can you elaborate please?
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hsbontop
Re: Extruder problems
June 14, 2015 11:26AM
Quote
nophead
If you are using the standard Mendel90 extruder it only works with 3mm filament.
I changed the scad to work with 1.75 mm filament.

Quote
nophead
It might work or it might not close far enough, depending on the hobbed bolt. However you don't want a geared extruder for 1.75mm filament as you want to drive it 3 times faster with 1/3 of the force. Having it geared will limit your retract speed.
I replaced the original 11:39 gears with 23:27 to compensate for the lower speed.

Edited 1 time(s). Last edit at 06/14/2015 11:56AM by hsbontop.
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hsbontop
Re: Extruder problems
June 16, 2015 05:13PM
Stl's posted here http://www.thingiverse.com/thing:884248
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