Direct Drive Bowden Extrustion Speed

Just finished building my delta with direct drive bowden, using a 0.4mm e3d hotend and 1.75mm filament.

What sort of extrusion rates are people achiving with this sort of setup?

At the moment I am using PLA and hotend temp of 180 and I can only get to 3mm/sec. This is only 6mm3/sec, which is half of what I used to get with my 3mm geared non-bowden setup on my old i3.

Iv currently got the trim pot set to 0.5V and the stepper just keeps skipping. What do you normally have the trim pot set to with this sort of setup?

I recently posted this [forums.reprap.org] which you may find helpful.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Why don´t you raise the temp? I´m printing PLA at 200-210°C all the time.
I got skipping once, when I tried to print bridges at 195°C. But that´s all related to the filament.
-Olaf

180C is possibly a little low for PLA, although I often use 180C after the first layer. As for the trimpot setting, I suggest you adjust it to run your extruder motor at 80 to 85% of its current rating, if your driver can do that without overheating. The corresponding voltage will depend on the value of the sense resistors in the driver modules, which may be 0.05, 0.1 or 0.2 ohms. Using electronics with software control of stepper motor current makes this sort of adjustment much easier.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Im a little reluctant to just raise the temp because im pretty sure I should be able to get much higher flow rates with this filament at 180C. Also from past experience the print quality starts to deteriorate when the temperature is increased.

With exactly the same filament at 3mm and using a geared cold end I could get just over 12mm3/sec before the hobbed bolt started stripping the filament, whereas with this I can just about get 6mm3/sec before the stepper skips.

Im beginning to think the direct drive setup just doesn't have enough torque to match the geared setup. Im gonna try switch to a slightly more powerful motor and use dc42's 85% suggestion and see how I get on, but im not hopeful ill ever be able to achieve 12mm3/sec again.

First thing on the list of thinks to print when its up and running is a new geared extruder!

Lesson learned, DONT use cheep motors for direct drive extruder!

Switch from a 36Ncm cheep motor to a 40Ncm wantai motor and the speeds are much better! Still not quite the same flow rate as the direct drive but closer.

Geared extruder is still first thing on the list of things to print tho.

Whats eveyone elses thoughts on direct drive?

I´m using an all metal MK8 clone with a relative big drive gear ( IIRC 13mm dia, non hobbed ) My stepper is 0.4A and barely gets warm, because of the good heatsink and cooling.
I was able to print at speeds, where my acrylic frame was way beyond its comfort zone ( 100mm/s with 6000mm/s^2 acceleration ), but the extruder never had any issues.
-Olaf