Custom Direct Driver Extruder

Hi Everybody!
After seeing some of the great modifications people have made to their Tantilli (sp?), I was inspired to design a direct drive extruder and thought I would share what I've made so far:

Extruder

The design uses 3mm filament and a Mk7 drive gear. It also uses a 608 skate bearing as I still have a ton laying around from the Tantillus construction. I tried printing out a test cube but the result was quite poor:

Test Cube

I'm still playing with the steps but started off at a baseline of 100 (the above image was printed using a value of ~125). I'm having a tough time dialing in a good e_step_per_mm as 125 seemed to be pushing too much filament into the hot-end, producing what looked like jamming and loss of grip at the drive gear but 100 didn't seem like it was providing enough... oh well, I'll keep at it.

Cheers!

Looks good. I like that it is so minimal and does not use any special parts.

From what I have read it is very hard to print 3mm filament with a direct drive extruder. The common recommendation is to not even attempt it and to only use direct for 1.75mm and to use a geared extruder for 3mm.

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Yeah, after a couple more test prints, I would have to agree that a direct drive extruder, at least when using a normal NEMA 17 motor, might not work out that well for 3mm. The bottom solid layers of the cube turn out well but once things start to speed up for the sparse infill, extrusion gets inconsistent at best. I might try one or two more test prints just to make sure I'm not missing anything but then it's back to the drawing board

You could print at the same speed for all parts of the model. That is how the Ultimaker and Cura do there printing. The only reason we speed up for the infill is to save a little bit of time.

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Definitely worth a try then... I'll report back

EDIT:

So after a few more test prints, I've decided to go back to a gear-driven system as I was never able to get through the sparse infill with any usable results.

Edited 1 time(s). Last edit at 07/23/2014 01:41AM by Nick101.

If you want to keep that simple design the planetary gear stepper works a treat with that set up.

http://www.omc-stepperonline.com/gear-ratio-51-planetary-gearbox-high-torque-nema-17-stepper-17hs191684spg5-p-40.html

Cheers
Keith

Quote
Robonz
If you want to keep that simple design the planetary gear stepper works a treat with that set up.

http://www.omc-stepperonline.com/gear-ratio-51-planetary-gearbox-high-torque-nema-17-stepper-17hs191684spg5-p-40.html

Cheers
Keith

Just be aware that motor has an 8mm shaft and you will not be able to use the mk7 gear. You would need something like a "mini hyena" to fit over the shaft.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

Good point, I think I pointed to the wrong motor but 5 to1 gearing is good, I think you can get the motor with the right shaft. The other option is get a hob that fits the 8mm shaft.

I am printing ABS for the first time today. Its stinky and my bed takes ages to get to temperature. Material requirments suck sometimes. The tantillus is printing good though. Printing on blue painters tape and the machine is still runninng nicely on 12 volts.

Cheers
Keigth