Problem with filament restarting after retraction

Hey everyone... Have a question... Today I printed some calibration cubes and found that they were slightly undersized. I calibrated the extruder and came up with a new steps_per_unit number. After making the change to firmware, I reprinted the calibration piece and found that while my measurements were pretty much spot on it now seems to be taking longer than normal to start extruding filament after a retraction. This is evident when doing one or two perimeters on a smallish piece. The only things I have tried was to reduce the retraction amount from 1mm to .5mm and reduce the retract acceleration from 2000 to 1500. I have also check my mechanical setup; gear mesh on the extruder is good, everything is good n tight, hobbed bolt is clean and aligned with the hole etc... The changes I made helped a bit (starts sooner but still leaves gaps) but now I'm getting more stringing between walls. Just wondering if anyone here might have an idea on what I could try next as I'm at a bit of a loss on what has caused this.

Pic one: First print, good quality but cubes were undersized by about .5 mm. Used two perimeter walls.

Pic two: After calibration, perfect sizing but have gaps between walls and fill because only one of the two perimeters gets printed. Takes about one lap around the part to get things flowing consistently again. It's very apparent after a change in Z

Pic three: just to verify, set walls, top and bottom to one layer. problem becomes more and more evident the higher you go and the smaller things get.

Thanks for any help that can be provided.

Andy

Depending what slicer you are using, there may be a setting for extra length after retraction. I know it is in Slic3r cause I had to use it the other day for the thin wall calibration cube I was printing.

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Quote
gmh39
Depending what slicer you are using, there may be a setting for extra length after retraction. I know it is in Slic3r cause I had to use it the other day for the thin wall calibration cube I was printing.

Hey, thanks for the reply. I was using Slic3r, latest version.. whatever it is. I tried using the extra length after retraction feature and it did help a little but not much. I spent about two days working on the issue with little success. As a last ditch effort I decided to try and experiment with Cura, which I had little experience with but had heard good things about. After slicing with Cura as my slicing program, my problems disappeared. Not only am I getting very clean cutoffs and restarts of the filament but I'm able to run at a much higher speed than I was ever able to in Slic3r. My results have been fantastic. I'm very happy with this slicer and I think it's going to be my new primary. In addition to this, it does a much better job at generating support material. With slic3r, I would get alternating support structure/main structure layers making the object unprintable. This doesn't happen in Cura. IMO, Slic3r is a little too buggy for me.

Here are some pics of my results. First is natulus gears sliced with Slic3r, pretty much default settings. Second is the same thing, again sliced with slic3r but with extra length after retract enabled. Third is the gears sliced with Cura, same basic settings as Slic3r. Not only did the Cura version come out better but it printed in about half the time. This is the first object I have been able to print with my printer at 100% feed rate.

Oh, and buy a cutting mat theres always tears in my heart when I see someone use their desk as a cutting surface

Ontopic:
Cura isn't perfect, but for me too, it works twice as fast and gives 'nicer' results.
This was for me the best addon to Cura: [wiki.ultimaker.com]

That plugin can configure the bed temp after # of layers to change. Keep in mind that the script needs a small change in order to work with the latest version of Cura, the change in the script can be found in the comments below on the wiki page of the plugin!

Edited 2 time(s). Last edit at 02/01/2014 06:33PM by Ohmarinus.

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Ohmarinus
Oh, and buy a cutting mat theres always tears in my heart when I see someone use their desk as a cutting surface

Its not a desk, its a work bench. :-) A cutting mat that size would cost a fortune.... If that bothers you, you should see the solid oak end table I have my reprap bolted to.

I'll check the plugin out... Thanks for the tip.

Haha, okay, but close to where I live they sell A3 cutting mats for 1.70 euros, doesn't have to cover the whole table ofcourse

Oak table with a reprap bolted to it!!! The horror