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quack3d

Under extrusion after every layer change

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Hi.

 

I've made a small cylinder with 0.5 mm walls and I try to print it in Cura with my ProFab3D Mini V3 (essentially a Monoprice Select Mini v2). Unfortunately I'm getting under extrusion after every layer change. I'm trying layer heights at 0.3 and 0.35, changed layer width, z seam alignment, optimize wall printing order, different temperatures, different filament, different flow, different print speeds (usually try 20 mm/sec on outer wall), jerk, acceleration, disabled coasting, etc. Nothing seems to work.

 

I've tried 4-5 different Cura versions, and 15.04.06 seems to not have this problem. However, when printing it in that version the width of the wall is thicker than it should be.

 

And for some reason it prints beautifully in Slic3r, but with a more noticeable Z seam. The toolpath is different between Cura and Slic3r. Where Cura goes back and forth from the seam (after enabling Optimize Wall Printing Order), Slic3r prints in one direction round and round the circle.

 

Suggestions?

wMfXZW3.png

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I was going to say try 20mm/sec but you did.  Wow - even at 20mm/sec you get that kind of underextrusion?  

 

What are the jerk settings, acceleration settings, and what is travel speed?

 

On UM series printers typically jerk=20mm/sec, accel=5000mm/sec/sec and travel speed at least 150mm/sec.

 

You want it to change layers as possible which means you want it do decelerate as fast as possible (basically stop instantly and change layers and start up again) with the fastest possible Z acceleration such that the Z axis just "clicks" and then starts right back up without losing a beat.

 

Right now I think it's pausing at the layer change, over extruding, then underextruding as it speeds back up.  Thinner layers should help (such that the nozzle pressure is lower).

 

Also look at the "spiralize outer contour" feature which doesn't need to change layers.

 

Could you show a picture of your model?  Ideally you want to give cura a model of a solid cylinder and choose spiralize which will only print the walls like this.

 

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@obewan The suggestion to use Retract at Layer Change with Retraction Extra Prime Amount kinda helped. I had to set it to 1 mm3. However, the wall is thinner in the beginning (where layer starts) and ends thicker. 

 

@gr5 At the moment I haven't enabled acceleration or jerk control. I have no idea what to try there really and in Slic3r acceleration is set to 0. It does look like it's using too much time changing layers like you suggest. It seems faster in Slic3r where I don't have this problem. I've already tried the Spiralize Outer Contour and it printed beautifully (except for the first 3 layers for some reason), but it's not something I can rely on for all kinds of prints obviously. The model is attached.

Cylinder.stl

Edited by quack3d

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Here's my take on this. It's (yet another) attempt at printing a wall that is not a multiple of two line widths wide. Cura really doesn't do walls that are not multiples of two line widths wide very well at all. As a workaround, enable the wall overlap compensation and also set "Minimum Wall Flow" to something like 30. Probably setting Outer Before Inner Walls is worth doing as well. That combination should suppress the second traversal which cannot be helping. YMMV.

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2 hours ago, quack3d said:

t I haven't enabled acceleration or jerk control.

good.  Don't.  Those will help with "ringing" but other than ringing it will make quality worse.  Especially under and over extrusion issues will be worse.

 

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I tried enabling just Compensate Wall Overlaps. That didn't help. Enabling Outer Before Inner Walls helped a bit but not completely. Best workaround so far is Retract on Layer Change + Retraction Extra Prime Amount to 1,5 mm3. 

 

But I still can't find the Minimum Wall Flow setting. The only 'Wall Flow' I find is 'Bridge Wall Flow'.

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There is also the scalable extra prime plugin that you can install.  It allows a range of extra prime based on distance traveled when not extruding and you can optionally enable extra prime for all movements... not just retractions.  You really need a few prints that exercise movements (without extrusion) to close, medium, and far distance to get it dialed in which can take some time.  Different types of filament ooze out at different rates though.  I tend to just print regular PLA of the same brand though so it works for me.  Maybe that feature should have settings per filament chosen.

 

EDIT: Note that the scalable extra prime plugin doesn't work (doesn't change extrusion amount) until you use an object that has somewhere around 15 or 16 layers (don't remember the exact number) for an object for some reason based on my testing.  I don't know if that is on purpose or a bug.

Edited by Adam324

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