The END OF OOZE

Posted on Slic3r issues on Github: Feature Request: Ooze Retract While Traveling. The end of ooze!

A small continuous retraction while traveling keeps negative pressure and eliminates oozing. This is very easy to accomplish:

Add an option to Printer Settings, Extruder1, Retraction: Traveling Ooze Retract Length. This is the amount to retract while traveling. This length is added back when un-retracting.

I wrote a post processor that I am using to test many techniques I'd like to see in Slic3r (see Feature Request: Coast #3014) and tested Ooze Retract While Traveling with my .571mm bore all-metal hot end with very long (850mm) Bowden tube. It always oozed, and now no more ooze! I was able to reduce the retract length from 6.8mm to 4.6mm + used 1.7mm of ooze retraction.

I'm posting it here in General because it's so simple - I hope all slicers will incorporate this technique!

A side note: too much retraction with an all-metal hot end can hinder the beginning of the next extrusion (see discussion in issue 3014).

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!

Interesting approach. I've seen reports that slowing down the retraction speed helps. This would seem to take that concept one step further. I wonder if you would get basically the same thing by slowing the retraction speed way down, or if it is still beneficial to have a quick retract followed by a slow "maintenance" retraction. My guess is that the real world behavior is an exponential of some sort so your two speed retraction system might do a pretty good job of following the curve of pressure decay. And it would be quicker overall than a single slow retract.

Good points.
I've done a good deal of testing with retraction (including testing retraction while coasting to the end of a line, see link above). Slowing down retraction isn't the answer - what this does is create a larger blob at the end of the line as the nozzle is stopped when the retraction is happening - the longer the retract time then the larger the resulting blob as the pressure is removed.

You are right, the two stage retract is faster - for one thing the initial retract can be slightly less, and the Ooze Retract while traveling takes no extra time. The un-retract takes the full time, but in my case the total un-retraction needed (regular + Ooze Retract) was less.

I am also testing early un-retracts (starting the un-retract x mm before the next print position).

Edited 2 time(s). Last edit at 09/28/2015 07:31PM by Paul Wanamaker.

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!

I am withdrawing the feature request.
After much further testing I find that I was incorrect in my assumptions.
A well tuned retraction amount does the same and better than a shorter retraction amount + an ooze retract while moving (for my printer) - there is less stringing. Notes in the Github link.
Sorry all.

Thanks for the research Paul, I've been optimizing my bowden setup too. I use a 550mm bowden tube, 2000mm/s2, 65mm/s and 4.5mm length retractions. No blobs and some minor stringing with flex and nylon filaments none with abs and hips.
What's also important is that there's no movement in the bowden tube and the connectors should be tight.

There is no reason to appologize Paul. It's inquiring minds like yours that advance the art. Keep up the good work.