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Retraction Setting

Posted by academicdave 
Retraction Setting
February 24, 2014 10:36AM
I am having trouble getting a good print when the area being printed is small, i.e. small diameter cylinders. It seems to me that i have to much plastic, and the plastic starts "piling" up too much on one side, like there is extra.. It happens only when the area is small. For prints like a wall I don't get this problem. I am wondering if I should set the "Retraction" length higher (using Slic3r). Right now I have it at 1.68. I don't think that it I am extruding too much plastic all the time as when I print the .4 calibration wall I get very near .4, like .41 for most of the wall. Below are some pictures of what happens.

Photo One
Photo Two
Photo Three

And a different piece that gives a really clear picture:

Photo Four

Should I up the retraction length? It already seems high to me, or is there some other problem here?
Re: Retraction Setting
February 24, 2014 12:53PM
Maybe it also has something to do with the layers not getting cooled down enough? I'm a newb but I have had this sort of problem when printing small layers. It helps to print multiple objects to increase the layer/cooling time. Still the pictures do you show a lot of stringiness so there does indeed seem to be too much oozing going on. I recently asked about retraction length on the the forum and 1-1.5 mm should be enough if printing at 185C or a little above, to prevent oozing. What temperature are you printing at? How did you arrive at that retraction length value if I may ask?


Re: Retraction Setting
February 24, 2014 01:52PM
I print at 185, and even in the first few pictures, where it is printing lots of small sections I still have the problem, ie there is plenty of time for the piece to cool. I am pretty confident that it is not a cooling problem, that there is just too much plastic.
Re: Retraction Setting
February 24, 2014 02:42PM
Ah ok, I hope some experts can chime in here.
Re: Retraction Setting
February 24, 2014 02:49PM
It looks to be an overhang problem.

A couple questions;

What material is it PLA or ABS?
Is the fan on 100% speed during the print?
How many perimeters are you printing with?
Re: Retraction Setting
February 24, 2014 03:40PM
Fan at 100%.

Have to check later but I think just one perimeter.

I think it does happen more at overhangs, or more precisely you can see it more at overhangs, but I do notice it at other times as well. Now this may or may not be related, but when I print a hollow box with random starting points there can be some "strings" that dangle inside the box. And if I stop infill mid print you can see some extra strings as well in the hex pattern. But maybe these are separate issues? Is there a way to just test overhangs and a method for testing retraction? You can see in the image below the "strings" I am talking about, one left in the corner. I cut most of them out, probably like 5-6 of them, some stretching across the width of the box.


Just checked, yes its 1 Perimeter.

Edited 3 time(s). Last edit at 02/24/2014 05:41PM by academicdave.
Re: Retraction Setting
February 24, 2014 06:09PM
When you print overhangs, you need to have more than 1 perimeter. For steep overhangs I usually use 3 perimeters, this should help prevent the previous layer from curling up. Lower layer heights also help with overhangs.

The strings you are talking about are probably from retraction or too much filament being extruded. Make sure you calibrate your E-steps and measure your filament diameter at a few different points.

In order to check retraction and overhangs you can print the following calibration piece from thingiverse. There are others you could search for as well.

Re: Retraction Setting
February 24, 2014 07:53PM
Thanks that was tremendously helpful. I printed up that piece, changed some settings in Slic3r and after a few itterations managed to get the following print. The 35 degree overhang is fine and just a minor mistake in the 45. 55 and espeically 65 did not turn out great. Is that too much to ask for or is there a way to get this even better?

Re: Retraction Setting
February 25, 2014 11:10AM
Good overhangs more than 45deg are harder to achieve but they are possible. You can try lowering temperature by 10C which should help, and using a high end filament will also help (Colorfabb).

Re: Retraction Setting
February 25, 2014 02:38PM
Excellent. Thanks so much I have been trying for a while to figure out what my issue was and this has definitely really improved the quality of my prints.
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