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Adrunodro

Bumps at the beginning of the layer or travels

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Posted · Bumps at the beginning of the layer or travels

Hi guys,

I have recently got Creality CR 10S and my models are having some problems I don't know how to solve. They have some little bumps on the surface and in the slicer I can see they all are likely on the beginning of the layer or on the end of a travel movement. Halving the speed and acceleration of travels and the acceleration of walls some improvement can be seen but I can't get a perfect result. Y have tried to tense the belts but it didn't work. Does someone have any advice for me?

IMG_20180923_233039.jpg

IMG_20180923_233410.jpg

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Posted · Bumps at the beginning of the layer or travels

I have seen in CURA that the position of the bumps matches the beginning of the outer wall line. I'll upload the CURA project when I get home.

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Posted · Bumps at the beginning of the layer or travels

If this is printed with multiple models at once, or with priming tower or so, it could be that the nozzle leaks while traveling through the air, and then deposits that blob onto the model when arriving at the edge? If this is the case, printing slower and cooler should reduce the effect (=less pressure in the nozzle, and filament is less liquid), but it is hard to eliminate totally.

 

If this model is printed alone, without the nozzle traveling elsewhere, the cause must be something else. Maybe settings? But I am not using the latest Cura version, so I can't say anything on that.

 

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Posted · Bumps at the beginning of the layer or travels

I printed it alone and without prime tower. Could you tell what version are you using? Are you using a CR 10 as well? 

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Posted · Bumps at the beginning of the layer or travels

Try turning off "outer wall wipe distance".  (set to zero).  Let me know if that helps.  I'm a bit skeptical about that feature but haven't messed with it.  Let us know.

 

Also you can try cutting the speed in half just to see if that helps.  That often helps.  You can do it in the TUNE menu.  Not just the outer shell speed but all the speeds as if it's printing faster on inner shell then it tends to over extrude when it hits the outer shell.

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Posted (edited) · Bumps at the beginning of the layer or travels

Hi Gr5,

I have tried both in the same printing (Tune>Speed>50%&outer wall wipe distance=0) and the result isn't good. I thing outer wall wipe distance affects at the end of the outer line but in my case the problem happens on the begening of the outer wall and the nozzles drags the over extruded material so now I think the problem is over extrusion as you said. I'm attaching the project, I thing the artifacts take place on the layer 18,20,26  on the right side of the benchy and 14,15,16,17,19,21,23,24 on the other side

IMG_20180924_194000.jpg

IMG_20180924_194009.jpg

Test_6_Outer_wall_Wipe_0.curaproject.3mf

Edited by Adrunodro

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Posted (edited) · Bumps at the beginning of the layer or travels

I have printed another attempt without retractions and the result looks as previous one...

Edited by Adrunodro
my crappy English

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Posted · Bumps at the beginning of the layer or travels

I have got a pretty decent print by changing the place where nozzle begins the outer layer. Problem isn't solved but it's less obvious. The setting is something like Hide Seams, I honestly think that this setting has an internal mistake as when I set "Hide" it places the seam anywhere and when I set "Expose" it place the seam in a corner, where bumps are more difficult to detect. This behaviour is the opposite of the one that is described in the help. 

IMG_20180925_145525.jpg

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Posted · Bumps at the beginning of the layer or travels

I think "hide" uses a random place to start the new layer and therefore it should be hidden because it is distributed over the whole object, ever layer in another place.

 

But depending on the object it could be better to place it explicit in a corner.

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Posted · Bumps at the beginning of the layer or travels

I get the same result on the Ender 3. I tried different settings such as going as high as I can on Coasting and a negative Retraction Extra Prime Amount. None of it seems to help so far.

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Posted · Bumps at the beginning of the layer or travels

So if you look 2 and 3 photos above at the side of benchy - those look like play/backlash issues where sometimes the head moves farther than others.  In other words an intermittent hardware issue.  I could be wrong - it could be overextrusion for example due to speed changes (I like to set ALL printing speeds the same to avoid stuff like that).

 

play/backlash can be caused by high friction (one drop of light oil on all the rods helps and feel the friction with power off - compare X to Y) and it can be caused by loose belts (pluck the belt with head in corner - for a UM2/Um3 it should be around 90-130Hz.  Dont' know anything about creality printers.

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