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chrismrutherford

Retraction settings for ultimaker2+

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Hi, I'm printing one of the 3dlabprint planes, which is mostly hollow with some support structures.  Using the default settings and a speed of 60mm/s I had some under-extrusion problems leading to weak layers.   I have increased the flow % to 105 and also increased the PLA temperature to 215 degrees, and also slowed the print to 40mm/s and things are much better.  The 3dlabprint guide states the following:

Retraction

This very depends on your printer quality and filament.

If you find underextrusion at layer startpoints increase “extra restart distance” this value add some extra filament after retraction, 0.5-0.2 works (if your slicer is able to) 0.7mm retraction for non-bowden extruders usually works , for bowden 4-6mm is OK, we need retraction for all spots not only for outer perimeters!

Sometimes a little bit of vegetable oil applied before print on filament helps (200mm)

Does anyone know where I would make these changes, either in cura or ultimaker settings?  I'd like to see if these make things better, or allow me to increase the speed with out reducing strength.  Even with my current settings when printing steep angles there are some slight weaknesses between layers.

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Those problems have nothing to do with retractions. That's simply that the layer height is too high for the angle at that particular part of the print. The previous layer isn't providing any support for the next layer so it just floats in the air. If you look at the picture found here I think you'll see what I mean: http://support.3dverkstan.se/article/30-getting-better-prints#slopes-and-stair-stepping

What layer thickness are you using right now?

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You should check layer by layer the cura preview and see if it's printing on the air, or there's any error on the stl.

Also, just incase, what cura version are you using? Because if you use the new cura and statt to adjust Coasting, then you can get an effect like that if too high, but that would show on all the layers.

Um2+ uses a tfm/ptfe coupler, so the retractions ain't a problem up to around 5mm or more. As far as I know um2+ uses 3.5mm retraction or 4.5?

Anyhow, if it's your first time with um2+ first try a default normal profile and default settings. And from there start to adjust stuff. If there's really something wrong there it will be easier to debug it.

Oh also check that the size of your filament it's really 2.85mm, and if it isn't edit the filament size on the advanced settings menu on the printer.

Edited by Guest

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Here is a comparison of the layers with the photo.  

point15mm.thumb.png.a9c9565a50c648b7c20b4a3264c53685.pngpoint25mm.thumb.png.298b7efa4eab810e2c9d42beb70e32e5.png

The cura mesh with 0.15mm (1st image) layers seems to have tighter contours than the one with 0.25mm (2nd image), which I'm assuming would be less of a problem for the printer.  Both images contain the same photo. I'll try a print later with 0.15mm and compare.

Edited by Guest

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It's simply an issue with how you're slicing the object. Take a look at this image:

layer_height_example.thumb.jpg.93e608e347aa80ded492500556f1f114.jpg

I used a simple cube as an example and tilted it to get a similar angle as you have in your model. The first layer view is with a fairly thick layer height (0.2 in this example). As you can see, every individual line is hanging in the air, it has no support from previous layers. In the 3rd image from the left I've halved the layer height, the lines are close together, almost touching but there's still tiny gaps which would lead to the same problem you're having.

In the last one I halved the layer height again and you can see that the lines are fusing to each other, supporting each other.

Normally cura would print solid infill to help the lines in the first image hold together. It will then look like this:

infill_line_support.thumb.jpg.6c32634b90350ff1254b77fd59ae8ded.jpg

But it looks like you've enabled "Surface mode: Surface" so that you only have a single line for the skin of your model. This effectively disables that "safety" feature in cura I just mentioned.

I hope that makes some sense.

layer_height_example.thumb.jpg.93e608e347aa80ded492500556f1f114.jpg

infill_line_support.thumb.jpg.6c32634b90350ff1254b77fd59ae8ded.jpg

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If you level properly you can print with a better adhesion and his layers are split, and the first layer is important, but whatever.

 

Look at the pictures. Look at the brim, it shows near perfect bed levelling.

The issue is presenting itself a few mm up in the print. Bed levelling only affects the first 2-3 layers, after that it no longer has any influence on the print.

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