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yellowshark

How to remove these Cura artefacts?

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Hi, hoping someone can help me with how to stop these artefacts appearing on the surface of the semi-dome shown in pic 1. The primary settings were

Layer height- 200; speed – 60; temp – 220; extruder nozzle - .4; wall width – 1.6; infill – 40%; retraction speed - 40; retraction amount – 5.5; fan - standard setting ; filament – Faberdashery

DS1

I wondered if it might be blobs arising from retraction , so as seen in the next pic I doubled the wall width to 3.2, but with no effect. (in retrospect a flawed thought process)

DS2

What I did see though was that the horizontal line at 90degrees to the wall was clearly causing the artefact. This line results from Cura ending one wall and moving outwards to the next wall

DS2a

So remembering that Slic3r had the option to start the external perimeter before the internal perimeters I tried it in Slic3r with the same settings; thinking that as the “line” was moving away from the external perimeter rather than towards it, it might improve.

As you can see a vast improvement. (whether that was moving to outside in or just swapping to Slic3r I do not know)

DS3

So I am wondering if there is anything I can do in Cura (14.01) to get a quality similar to Slic3r? The one thing I do not really want to do is to change the layer height and print speed.

And also the top of the sphere is bad too – this is the first time I have printed a sphere geometry. Is there anything I can do to impove this?

DS5

This was printed in Cura with changed settings of layer height 100; speed 30 temp 210

 

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And also the top of the sphere is bad too – this is the first time I have printed a sphere geometry. Is there anything I can do to impove this?

 

From this thread:

http://umforum.ultimaker.com/index.php?/topic/3713-cura-13112-ignores-minimal-layer-time/

lluminarti says:

Expert -> Open Expert Settings -> Cool Head Lift

I can confirm that this setting greatly improves the look of the sphere top! Almost no blobbing.

 

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The warts look to me like the classical blobbing problem caused by pressure increase/decrease in the extruder. For example, Sailfish firmware has the JKN algorithm to compensate for this: http://www.makerbot.com/sailfish/tuning/

Now what you can do is make sure the infill and perimeter speeds are the same. If you can, increase the acceleration for travel moves. The workaround in Slic3r of changing the perimeter order is sometimes effective as you see but it's sort of masking the real problem.

About the top of the sphere there are lots of options to help with that. You can increase the minimal layer time, make sure max fan speed is 100%, and decrease the minimum speed. You can also print two objects at the same time, thereby giving more time to cool.

 

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