The dreaded Bowden OOZE! I've recently changed my extruder from Direct-drive to a bowden

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(Chris Wilson) #1

The dreaded Bowden OOZE!

I’ve recently changed my extruder from Direct-drive to a bowden style extruder. My prints are looking much better from the elimination of weight on the Z Gantry (The extruder setup was quite heavy.) however, I’m faced with the issue of ooze. I understand the relation between hysteresis and distance between the drive gear and the hot-end. I’m wondering if anyone’s managed to come up with a solution?

I’ve tried extending my retraction length (up to 7mm) and increasing the speed (up to 60mm/s) but it doesn’t seem to have any effect. I’m also getting blobs at the perimeter seam, I’ve adjusted my jerk settings, checked my extrusion steps/mm which are all within tolerance.

I’ve also read theres a setting in Marlin’s Configuration_adv.h:

#define FWRETRACT // not fully tested

is this an option? Has anyone enabled this setting, then enabled firmware retraction in Slic3r?

anyone have any suggestions? Sorry for the poor picture quality.

Thanks in advance,

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(Ryan Carlyle) #2

I’d stick with smaller retraction distance at higher speed/jerk as long as you don’t go over Marlin’s step generation limit of 40khz. It’s the quick yank that clears the nozzle orifice, not the distance. There’s really no good reason for 7mm unless you’ve got several feet of tube.

And make sure there is ZERO play in your bowden fittings – eg print some clips to keep the pushfits immobilized.

(Chris Wilson) #3

@Mark_Rehorst Good question - I don’t know off hand (at work) - I’ll get a length this evening. I ordered 1.5M, but obviously I didn’t use it all - I think about half? I know I can definitely shorten it, but I’m waiting for the E3D V6 to show up before I finalize lengths. If I were to guess, I’d say 650 - 700mm?

I’ve also since shortened the retraction length as I found increasing the length didn’t really offer any noticable change. I didn’t see any binding or jamming in the heat brake when I had retraction that high though.

(Greg son) #4

What is your travel speed?

(Ryan Carlyle) #5

I run 2.5mm at 100mm/s through a ~400-500mm tube with an E3Dv6 and 5:1 geared stepper. Depending on your motor torque and such, slower speeds might actually be better. Try something in the 2-3mm range and play with speed and jerk and see what happens.

(Chris Wilson) #6

@Greg_son

Perimeters: 60mm/s
External Perimeters: 25mm/s
Infill: 50mm/s

Non-print moves: 90mm/s

(Greg son) #7

With bowden you actually can go faster on travel speed, try 120

(Chris Wilson) #8

@Ryan_Carlyle Thanks, I’ll give that a shot.

(Chris Wilson) #9

@Greg_son You mean on non-print moves?