foehnsturm

If I did math right: approx.140 rpm and 950 steps / s (half stepping)

A short extrusion test video. With years old UM silver PLA @ 210°C, underextrusion starts at 115 mm/s (9.2 mm3/s). But it's not the stepper skipping steps but filament slipping. If I increase the idler arm pressure by hand it would go beyond 140 mm/s. 100m/s @ 0.2 layer is ok for me but more should be possible with a stronger idler arm.

Stepper: SY20STH42-0804A (http://cncshop.at/index.php?a=4076&)

I still like the flexdrive because it realizes direct extrusion with almost no additional weight. However, I had some extrusion issues with short paths and frequent retractions in between. Perhaps some torsional flex, perhaps my setup wasn't dialed in perfectly. It would be very interesting to hear some other flexdrive experience (Team Ultimaker ?!). Compared to this, the NEMA8 direct drive gives you absolutely on spot extrusion control (retraction distances < 0.5mm). It's even possible to print flexible filaments with retraction on, because the tiny movement doesn't cause any unwanted filament jam.

FlexiFil and his friend Lay-Fomm who has to sit in water for the next days ...

... ugly, I have to admit. But as it's a small motor it's not very loud.

I'm still using the http://umforum.ultimaker.com/index.php?/topic/3890-the-crossflow-fan-approach/?p=30643.

.. works very well with FormFutura FlexiFil: 0.8 mm shell, 0.15 mm layer, no infill, 40 mm/s, retraction 0.4 mm @ 5 mm/s, 215 °C

I printed my extrusion test cylinder again, ColorFabb PLA @ 206°C: Perfect extrusion up to 9.6 mm3/s (120mm/s * 0.4 nozzle * 0.2 layer) My conclusion so far: a worm geared NEMA8 direct extruder is strong enough. The additional 100 gr weight is partly compensated with the absence of fans or heat sinks on my print head. The head still remains substantial heavier than the standard head though. However, the possibility to use any filament and the absence of any strings may be of more importance. .. yes, the motor is intentionally tilted :wink:

I just finished the first larger print with the new setup with the stronger NEMA 8. 3 hrs, ColorFabb XT @ 240 C, 0.15 mm layer, 40 to 70 mm/s Close to perfect results. The additional weight is almost exactly 100 gr ( stepper 80 gr, worm gear 10 gr, drive gear and bearings another 10 gr) Don't know about the UM2 or UM+ electronics. But the only thing to adjust should be the stepper current (HW on the UMO, SW on the UM2 and UM+ I think).

This is actually already underway http://www.brewie.org/ Will be cheaper and of more practical use compared to an UM3

I'll upgrade to a NEMA8 with 300gcm and 80g weight (SY20STH42-0804A). If I remember correctly, steps/e on the UM2 is set to 282. So one might consider to operate the NEMA8 in full stepping mode which gives 380 steps/e. Additionally, as I read somewhere, half stepping gives the lowest torque output (but differences are within 5-10%). At the moment, a BOM or detailed project description is a little complicated: I machined down the stepper drive shaft from 4mm to 3mm, removed half of the MK8 drive gear and glued it etc. There is really not much room as you can see. For the next iteration I'll use this worm gear http://www.ebay.de/itm/Schneckenrad-Schneckengetriebe-Schnecke-Modul-0-5-Messing-Stahl-/191027866545?_trksid=p2054897.l4275 (German)

Hi Jeff, Problem still solved? Since yesterday I see exactly the same problem on my UMO, with exactly the same sound. The displacement is random from 5 to 30 mm. It starts to occur within a certain z range and happens at relatively slow speed. Disassembled and cleaned all rods, the printhead moves easily, tightened all screws. :?:

I tried the normal print profile the last two days and I would say yes. However I made the inner shell speed a little slower and the outer shell speed a little faster because I think the extruder lag might produce some uneven extrusion with that abrupt speed changes. BTW: the new top/bottom surface speed worked well for the bridging test I did today.

I did some test prints today. https://www.youmagine.com/designs/make-2015-3d-printer-shoot-out-test-geometries Extrusion temp seems to be a little high but for a first try I'm quite satisfied with this. Sliced with Cura 15.01. layer height: 0.1 mm (bridge 0.15 mm) speed: inner shell 60 mm/s, outer shell 40 mm/s (except resonance test), top/bottom 30 mm/s I had to learn about max revs/min of steppers. With a 1:40 worm gear 45 mm/s would transform to 5400 revs/min for the extrusion stepper .... Settings are now: 0.3 mm distance @ 5 mm/s

I can't see a big difference so far. In theory it should be worse than a UMO or UM2 but way better than direct extruders with bigger steppers. BTW, can anyone post the weight of a UMO or UM2 print head?

I did some extrusion tests. 5.8 mm3/s is the save limit at the moment. Which is very much ok for most prints. Above 6 mm3/s filament starts to slip. Increasing spring pressure helps but soon the stepper starts skipping steps. Right now it's a NEMA 8 with 1.8 Ncm holding torque. I'll change to a NEMA 8 with 3.6 Ncm. If everything works as intended, it should be possible to get a direct driven extruder capable of 10 mm3/s with only approx. 100 grams additional weight.

Hi, I'm very sorry but there are there are not enough inquiries for are reasonable production lot (which has to be some 100 pulleys).

Hi UltiArjan, No spring pressure adjustment so far. But that shouldn't be a big issue, Yes, it's one bolt for the bearing arm. For the steppers: As far as I know, voltage isn't important but current. Just adjust the stepper driver to the desired current (which should be equal or lower than the stock setting). http://reprap.org/wiki/Pololu_stepper_driver_board. Most steppers can be operated in bipolar (4 wire) mode. First print with Formfutura FlexiFil. There is still some room for improvement (layer adhesion).

After several months without any 3D printing at all I finally found the time to fix some issues with my latest project. So this is my modular printhead, now fitted with a direct extruder: a NEMA 8 stepper with a 1:40 worm gear, MK8 drive gear, 0.55 amp stepper current, microstepping set to 2, 760 steps/e. As expected, retraction works like a charm. Torque hasn't been an issue so far but the weakness of several idler arm designs. Right now it's reliable running with approx 70 mm/s @ 0.2 mm layer height. I didn't try to push it further as i'm printing some christmas gifts. Please don't look at the wiring :oops:

There is an improved version of the original mount on https://www.youmagine.com/designs/modular-printhead-ultimaker-flex3drive-merlin now. Less parts and print-optimized.

@UltiArjan, that's what I intended to do as well, so I will be interested in your pratical experience... But I postponed the order because their software only supports Windows right now, Mac support is announced for the first quarter 2015.

It's a heavily modified UM original: Merlin hotend, crossflow fan, Flex3Drive flexible shaft. Here is a The Merlin hotend uses airbrush nozzles which are available from 0.2 to 0.4 mm and I have had manufactured my own batch with 0.6 to 1.0 mm.

Simple Downlight Body: ColorFabb Woodfil Coarse (which sadly never made it to bulk production) and BioFila Linen Diffusion disc: ColorFabb XT Light shade (inside, not visible): Formfutura Flexifil Printed with a 1 mm nozzle (diffusion disc 0.4 mm) Light source: LED panel 100x100 mm, 2000 Lumen (equals approx. 120 W halogen)

the ?door? in first video: