Settings for Bowden Extruder (Oozebane?)

Hey!

SUMMARY: (Does anybody have a good skeinforge solution to the blobbing caused by a bowden cable? )

I've been getting awesome prints with skeinforge and a standard wade style extruder for a week or two now, and I just built a bowden extruder/ultimaker style machine. Everything seems to be working well, except I get massive blobs of plastic where the layers change.

I've tried using oozebane to account for the on/off delay of the extruder caused by the tube, and have gotten it to work a little bit. My problem is there are a few seconds worth of ooze when the extruder isn't reversed, but reversing alone doesn't solve the problem. Unfortunately oozebane and reversing do not play nicely together for me.

With both options on, the nozzle stops xy motion, reverses the filament extruder, and THEN finishes the last 6mm of path where oozebane kicks in. Ideally the extruder should be simultaneously reversing the feed and continuing on the oozebane path.

I'm printing at 120mm/s with a 30cm long cable, 1.75mm ABS filament, 2mm ID PTFE Cable, SF 41.

Thanks!

I run a bowden and had the same issue with blobs on layer change. My solution was to turn up the z speed to 5mm/s and no more blobs.

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I just reached 120mm/s with my bowden [forums.reprap.org] one of the things I did to get rid of the blobs at those speeds was to set my maximum E speed in the firmware to 600mm/s.

At least in teacup if you set the E_startstop_steps to 200 it will retract on its own at the above set speed of 600mm/s by 200 steps every time it goes from an extruding move to a non-extruding move and add it to the beginning of the next extrude move. You have to set the retraction to 0 in the dimension tab of skeinforge or it will conflict.

I assume this is the same thing that the retraction settings in skeinforge do, but when trying to use them I found it could not react in time and happened later because it was another line of code. It may still work as long as you set your E max speed in the firmware to the highest speed you can run your extruder at when not extruding (600+). If it is not set high enough you will still have ooze where it pauses to retract.

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I'll have to try that. I upped the Z to 8mm/s and it helped, but was still a problem.

I assume 600mm/min not 600mm/s?

No 600mm/s 36000mm/m

That is as fast as my extruder will turn without the hotend attached but with the filament in it. I use teacups old acceleration set to 50,000 and its default is 500,000.

I went from having it set at 120mm/s (7200mm/m) to 200mm/s then to 400mm/s and found it improved the blobs until I reached what is my bodged extruders reliable limit of 600mm/s (36000mm/m). At 200 steps of reversal it still takes 166.66 milliseconds to reverse. I think I will now try reducing the E_startstop_steprs to 100 but I am not sure if that is enough to take up the slack and pull the ooze back.

Edited 1 time(s). Last edit at 05/20/2011 12:51AM by Sublime.

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OOPS just realized you are using SF41 and I am using 39 so my setting are extruded length. Divide them by 30 to get the input length. 600mm/s extrude = 20mm/s filament input?

So set you max at 20mm/s (1200mm/m)

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Just realized I was wrong again because you are using 1.75mm filament not 3mm so I don't know the math to convert it from extruded to input.

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Did you have to change anything in teacup besides e_startstop_steps to do firmware reversing? It isn't doing any reversing just increasing that number to 200. I have a feeling I'm missing something, though I am running an older version of teacup.

No I didn't change anything else. You can not have oozebane on or reversing enabled in the dimension tab. I am using [github.com] with the ramping set to 50,000.

I checked a Gcode file I've created and it has no negative E movements.

I also use relative E movements.

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I've got no oozebane nor reversing. I don't have any acceleration enabled, either. I wonder if some form of teacup acceleration must be enabled for it to work.

Maybe, The old teacup including the one I use has the ramping acceleration set to 500,000 originally but it makes for painfully slow builds. I went down from 500,000 to 250,000 then 125,000 then 75,000 then 50,000 and even faster but found it is to easy to skip steps any faster than 50,000. At 50,000 it accelerates fast enough that it almost seems like it is turned off.

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