New SeeMeCNC Extruder

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Re: New SeeMeCNC Extruder

Postby Simon » Sun Jul 14, 2013 8:22 pm

We made our own edition of the Rostock 3D Printer originally designed by Johann C. Rocholl.

One of the elements we spent hours redesigning is the Bowden Type extruder. It's available on our Thingiverse, it's worth checking out: http://www.thingiverse.com/thing:113127.
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Re: New SeeMeCNC Extruder

Postby kbob » Fri Jul 19, 2013 5:52 am

vgordin wrote:Have you guys used this with 3mm filament?


The EZStruder is widely reported not to have enough torque to drive 3 mm filament.
Bob
"If you didn't code it, it will never own you." (-:
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Re: New SeeMeCNC Extruder

Postby flickerfly » Fri Jul 19, 2013 12:25 pm

kbob wrote:
vgordin wrote:Have you guys used this with 3mm filament?


The EZStruder is widely reported not to have enough torque to drive 3 mm filament.


Isn't torque more a function of the stepper or is it not biting enough with the teeth that impacts the torque? When my bed gets loose and the hot end is right on top of the glass my 1.75mm filament will end up getting eaten by the teeth and I have a bite in the filament and lots of plastic inside. I've found I can clean that all out without taking any screws out with some strong puffs and a q-tip while running the extruder dry.
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Re: New SeeMeCNC Extruder

Postby orcinus » Fri Jul 19, 2013 1:29 pm

It is a function of the stepper.
Most 3mm extruders aren't direct drive.

Using a planetary gear stepper might work though?
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Re: New SeeMeCNC Extruder

Postby flickerfly » Fri Jul 19, 2013 2:09 pm

Are steppers not available in the right size with sufficient torque? I'm trying to learn why that option is being passed over.
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Re: New SeeMeCNC Extruder

Postby cvoinescu » Fri Jul 19, 2013 2:45 pm

flickerfly wrote:Are steppers not available in the right size with sufficient torque? I'm trying to learn why that option is being passed over.


Exactly. 3 mm filament is about three times the area of 1.75 mm filament, so it needs three times more force to extrude. It doesn't matter that it also needs to move three times slower, it's the torque, and hence the force, that's the limiting factor. It also needs more pressure between the filament and the drive wheel, which increases friction. 3 mm extruders work very well with geared motors, ideally in the 4:1 to 25:1 range. For gear ratios above 15:1 or so, even a larger NEMA14 is enough. The very reliable Wade's extruder in its various incarnations has a gear ratio between 4:1 and 5:1 and is driven comfortably by a medium-size NEMA17 motor.

I think the largest NEMA17 motor with the smallest available drive wheel would just about do it.
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Re: New SeeMeCNC Extruder

Postby flickerfly » Fri Jul 19, 2013 2:50 pm

Thanks for the thorough answer. I see why 1.75mm is becoming more popular.
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Re: New SeeMeCNC Extruder

Postby fma » Fri Jul 19, 2013 3:34 pm

If I remember what nophead said about the needed force to extrude, it is in power of 4 of the diameter... So, much more than 3 times the power needed for 1,75mm...
Frédéric
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Re: New SeeMeCNC Extruder

Postby cvoinescu » Fri Jul 19, 2013 5:17 pm

I believe that's based on some over-simplification, or it may be true for the same linear rate of filament advancement, which is not the case. In practice, to extrude the same volume of filament per unit of time, the force is probably more than three times as much, but not a lot more.
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Re: New SeeMeCNC Extruder

Postby orcinus » Fri Jul 19, 2013 9:43 pm

Re: more popular...

The reason it's more popular is the extruders are simpler and cheaper.
3mm is still the king in Europe, though. You'll have a much harder time finding 1.75 here than 3mm.

Both diameters have their pros and cons.
1.75mm is more expensive, for one. It's more flexible and will buckle more easily. Allegedly (forgot the source), nozzle pressures are slightly lower for 3mm.

Then again, 1.75 extruders are lighter, so can technically print better quality at higher speeds.
And the melt zone can be shorter.

And, then again, 3 is better suited for bowden setups (less backlash).

etc. etc.
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