This engineer claims 100 grams direct extruder. I want one

I'm using acceleration of 2000mm/sec^2 and 2mm retraction at 40mm/s. This works fine, despite your doubts. But it's still stringy...
IIRC, dc42 claims 15000Hz for the Due_RRF firmware for steps, so I tried 60mm/s retraction with occasionally failure ( 1 out of 20 )
It usually was the extrusion part after a successful retraction.

I'm willing to try your "lame" settings, maybe I get a nice surprise
-Olaf

BTW, the RAPS128 drivers at 16/1 microsteps can keep the stepper much colder than the A4988. I guess it's the faster current control loop?

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dc42
What is the inductance of your Nema 11 motor? Can you get a variant that has a higher rated current but lower inductance?

My apologies, it is of course the NEMA14 like it's supposed to be with 7.5 mH. There is a slightly bigger and heavier NEMA14 pancake with 5 mH available, but the longer housing would reduce the deltas bed radius even more. ( collision with the rods at some places)

We're getting there!

The suggestion to use less retraction length and speed helped a lot against stringing. But the blobs got worse...
I tried it one more time with 1mm retraction at 30mm/s, but the blobs didn't disappear.
If I find the time today I'll try 1.5mm at 35mm/s. There must be a sweet spot, still undiscovered.

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o_lampe
The dodecahedron was printed at 60mm/s & travel at 150mm/s. I thought, the faster travel the less stringing.

That has also been my experience. I can't see anything in your settings that looks questionable at all, everything seems within the ballpark of where I would have put it.

I'm glad to see that you're getting closer to a good set of numbers. I bet it's frustrating to trial something that, at first glance, should give amazing prints, but it doesn't perform as well as expected. Good luck with the tuning.

Edited 1 time(s). Last edit at 08/06/2016 10:03AM by nebbian.

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o_lampe
IIRC, dc42 claims 15000Hz for the Due_RRF firmware for steps

15kHz is the step rate at which the firmware switches to double stepping. The maximum step rate with just one motor moving is about 300kHz on the Duet Wifi, using firmware 1.15 beta. On the Duet it is probably about 200kHz.

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o_lampe
BTW, the RAPS128 drivers at 16/1 microsteps can keep the stepper much colder than the A4988. I guess it's the faster current control loop?

It's much more likely that they are cooler because you are running them at a lower current.

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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].

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o_lampe
We're getting there!

The suggestion to use less retraction length and speed helped a lot against stringing. But the blobs got worse...
I tried it one more time with 1mm retraction at 30mm/s, but the blobs didn't disappear.
If I find the time today I'll try 1.5mm at 35mm/s. There must be a sweet spot, still undiscovered.

Good to hear - seems to get better!

E3D's docs says:

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E3D
Excessively long retractions will cause issues by dragging soft filament into cold areas. E3D-v6 hotends need less retraction than most hotends. For direct extrusion systems you should use anywhere from 0.5mm-1.0mm, for bowden systems you might want to go up to 2mm. Retraction beyond 2mm is likely to cause issues.

Not sure, but maybe the severe blobs are caused by air being sucked into the hotend during retract, mixed inside to a nice foam and then extruded onto the print. I'd suggest to start from retract=0 upwards and see, how the stringing and the blobs behave.

Edited 1 time(s). Last edit at 08/06/2016 03:54PM by powdermetal.

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nebbian
I bet it's frustrating to trial something that, at first glance, should give amazing prints, but it doesn't perform as well as expected.

I was calling for trouble when I started testing a brand new extruder on an uncalibrated delta, so I partly expected to waste a full spool of filament for tuning.

Maybe it was all false alarm: I noticed the blobs mostly appeared on the lee-side of my part cooler. When I placed another fan there, the print got much better.

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dc42
It's much more likely that they are cooler because you are running them at a lower current.

I tested the extruder on a RAMPS with the ramps-test code.
The A4988 was set to 0.26V which is 0.32A and the stepper got too hot to touch. ( Crappy ramps-test code? )

Now it runs at 0.52A and stays cool with the RAPS128.

Ping.........!

Anybody advanced any further with this project?
I heavily modified the casing drawings to arrive at something suitable for my Kossel where the E3d hangs underneath the spider but a load of other diversions mean that I don't yet have a fully operational unit - but I am interested to hear how others are getting along.

Having recently moved house, my workshop is slowly getting back to being operational again (the 03D stuff sits in the office!), and this included a CNC mill and lathe which I intend to use to try some of the components in aluminium - especially the outer gear casing and probably the pin carrier and shaft. Update will follow when I get somewhere closer!

Regards,
Simon

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Simon0362
Ping.........!

Anybody advanced any further with this project?
I heavily modified the casing drawings to arrive at something suitable for my Kossel where the E3d hangs underneath the spider but a load of other diversions mean that I don't yet have a fully operational unit - but I am interested to hear how others are getting along.

Having recently moved house, my workshop is slowly getting back to being operational again (the 03D stuff sits in the office!), and this included a CNC mill and lathe which I intend to use to try some of the components in aluminium - especially the outer gear casing and probably the pin carrier and shaft. Update will follow when I get somewhere closer!

Regards,
Simon

We have hijacked this thread for quite a while with this thing and I just gave the discussion it's own home - please proceed to the dedicated Cycloidal Extruder Drive thread - see you there...

I have followed with great interest the whole thread and this is exactly what I was after: a concept that would crystallize into something real. I am a big fan of the cycloidal drive so this is so much more interesting to me.

While I hope this thread will continue to have folks show off their lightweight extruders concepts and prototypes, I am glad that your design got a well deserved new home.

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RepRap Lander concept on Concept Forge
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