Extruder problems

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Extruder problems

Postby fma » Wed May 07, 2014 10:48 am

Hi!

I'm designing a direct-drive extruder for 1,75mm filament, for a friend, and we have some issues. First, I have to say that I'm using such extruder for more that 1 year with success, but I only used ABS so far. Our problems are with PLA...

What happens is after some time, the filament is not pushed anymore. This happens when there is some retract. And I don't know if it is because we don't push enough on the idler, of if we push toot much! The gear is a MK7 from reprap.me. The notch is not very deep; could someone send a picture of a filament which as been pushed through such MK7 direct drive gear?

Thanks for your help.
Frédéric
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Re: Extruder problems

Postby cvoinescu » Wed May 07, 2014 4:22 pm

What's the hot end? Many all-metal extruders have trouble with PLA (which can sometimes be fixed with extra cooling on the barrel and/or cold end). Retraction and inactivity or slow extrusion can cause problems. Hot ends with a good thermal break, e.g. a PEEK or PTFE barrel, work much better with PLA. A well designed bore also helps: the J-Head, for instance, is trouble-free with PLA even with retraction or long inactivity times.
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Re: Extruder problems

Postby fma » Wed May 07, 2014 4:33 pm

The hotend is a E3D. Is has a fan on the cold end...
Frédéric
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Re: Extruder problems

Postby cvoinescu » Wed May 07, 2014 8:29 pm

I have one but haven't had a chance to use it yet*. It looks well made, but that doesn't mean it doesn't have the usual problems of the all-metal extruders with PLA.

* I know, wasteful to buy something and then not use it, but my spare time dried up more or less unexpectedly.
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Re: Extruder problems

Postby Coin3 » Thu May 08, 2014 3:21 am

I have been having the same issue with my E3D hotend & direct-drive extruder. It also seems to occur with the T-glase and Bridge nylon filaments that I just got.
I'll definitely be doing some research... the E3D forums seem like a good start: http://forum.e3d-online.com/
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Re: Extruder problems

Postby fma » Thu May 08, 2014 5:37 am

Ok, thanks!
Frédéric
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Re: Extruder problems

Postby evil2002usna » Tue May 13, 2014 11:34 pm

I use the micron eme extruder from ebay with its stainless steel raptor style drive gear. I can tighten the idler pretty tight and it keeps driving. I think the key is to have good idler tension, but your drive gear has to have alot of bite as well otherwise it slips on any resistance. I would look at a more aggressive drive gear

http://m.ebay.com/itm/181362261408?nav=SEARCH
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Re: Extruder problems

Postby fma » Wed May 14, 2014 5:27 am

Are these gears sharp enough? The teeth seem very flat... I plan to use a Hyena gear, or maybe this one:

http://www.ultibots.com/micro-extruder- ... m-filament

especially designed for 1,75mm filament.
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