Issue with all spherical internal walls towards top

[cloakfiend 995]

Hi folks, Not sure if anyone has noticed, that when I print pretty much anything hollow that has a spherical or curved top, the abrupt internal layer arrival towards the top drastically increasing time for the next layers ending in ruining the perfect surface. Its such a pity, can anything be done about a gradual wall building up slowly to prevent the sudden additional cooling time. I've noticed this for a while now, it affects me more as I tend to print in 0.06 so those printing in .01 layers warp less.

[burtoogle 513]

Hi, try increasing the top skin removal width setting...

 

[cloakfiend 995]

Hi yes im giving that a go now, but all it appears to do is move the sudden skin higher up the slant. I was after a slow incremental increase option? If there is one. Its the sudden increase in time that causes the layer line. The top skin is just not there one minute and massive the next layer. It needs to be graduated in for better overall layer quality! Ill see how this one goes....

[burtoogle 513]

Ah, sorry, I didn't really understand your original request. Don't know how to achieve what you're asking.

[cloakfiend 995]

Thanks for the tip anyway. At least i know what the setting is called. It should really be graduated into the size it becomes. Hopefully cura will fix this? Eventually. Lol.

 

Its even there after light sanding.

 

[eldrick 65]

Try Variable Layer Height.

 

[JCD 28]

You're using a 0.06mm layer height, are you sure that this size is correct accordingly to the stepper motors and mechanical transmission of the movement on the Z axis (for the gap appearing where you put an arrow)

 

take a look at http://doc.3dmodularsystems.com/what-is-the-best-layer-height-for-your-printer/

[cloakfiend 995]

Hi yes im giving that a go now, but all it appears to do is move the sudden skin higher up the slant. I was after a slow incremental increase option? If there is one. Its the sudden increase in time that causes the layer line. The top skin is just not there one minute and massive the next layer. It needs to be graduated in for better overall layer quality! Ill see how this one goes....no luck

I always get this weird line from the topskin regardless and its only because of the sudden different in time from one layer to the next. If it was gradual the line simply wouldnt be there.

 

...and I pretty much only print 0.06. Um2 and s5. This is my only issue!

Edited March 1, 2020 by cloakfiend

[cloakfiend 995]

This really should be looked at. It means there is always a visible line the moment the top skin kicks in becausecit doesnt ease in. Its just not there one minute and blam! Massive the next. Is there a way to graduate it in size manually over a few layers in cura?

[cloakfiend 995]

The topskin produces much cleaner tops with it than without it, so having the topspin is needed, but its a shame it doesn't ease in from one layer to the next as this would fix the visible line on the surface. Its not a matter of layer height, thats entirely unrelated. its a matter of layer time taken from one layer to the next.

[eldrick 65]

" I was after a slow incremental increase option? If there is one."

 

Yes, there is, such a setting. It is found at the bottom of Cura's settings, under Experimental, and is called Use Adaptive Layers..

[cloakfiend 995]

Hi @eldrick thanks for the info! could you elaborate on the 'Adaptive layers' setting how it works and what i'd need to set to make the top skin ease in instead of simply arriving on one layer. It would make my cute kitten models much easier to post process!!

Thanks.

[JCD 28]

I do'nt think adaptative layers option is the solution as the settings of cloakfiend at 0.06mm is already at the minimum avaiable

 

My analysis is  :

 

1) We have an  hemisphere to print (radius of 30 mm, 30mm high) and the higher is the layer, the thinner is the wall. THis is why at a moment Cura change the skon making from wall to top skin

 

2) on the picture below a drawing representing a zoom of the skin at the location of the change (and where the gap occurs)

the sphere is in green, the 394th layer with the gap is in blue.cyan, the white rectangles(0

4mm wide and 0.06mm high) are the filament printed.

The red rectangle is where there is a change in the quantity of overlapping prints. Below this layer, the outer wall has 5 overlapping prints and on higher layers it's only 4. If we continue higher, there would be 3, then 2 and so on with a lower skin quality and maybe even holes

 

 

3)this is why Cura change to the top skin printing

After my slicing tests, the higher the ratio wall_thickness/top_thikness, the later the  wall>>top change occurs.

The simplest would be to put the top thickness to 0, but due to the text above quality is poor

 

4) the other way is to make the wall thicker, but it will use a lot more material. The solution is to use 4 support blockers (with modify settings with overlap... option).

The picture below is the test I did with a the begining a 3 lines wall and then, with the support blockers, 4, then 5, 6 and finally 7 lines wall. Also check the outer wall before inner walls options in the skin settings (at least for the blockers) to get a better transition anytime the number of walls is increasing

 

Edited March 6, 2020 by JCD

[geert_2 557]

And what is the effect if you make the wall thicker? (Or thinner, to exaggerate the effect?)

 

I also have noticed that any sudden changes in layer-area to print, or in wall thickness, do show up as horizontal lines.

 

Try this on a small cut-out of your model, at the place where the problem appears. So you don't waste too much time and material.

 

[cloakfiend 995]

Reimporting the same model sounds long. And then doing all that box stuff. That top skin needs to be programmed to ease in oversay 5 or 6 layers. Maybe more. Its the only thing wrong with cura at the moment. It means you will never be able to print a perfect hugh res semi sphere without using filler. Which is exactly what i needed to. Make a sphere fron two semis. 0.06 has many benefits to lower reses and i think its neglected in cura. Everyone seems to love 0.1? 0.06 was the sole reason i bought one back in the day. I alread have 3 wall. I dont want mess around with 4 or 5 to fix an issue that shoukdnt be there. 

[JCD 28]

Maybe a different workaround is not to let Cura solve the problem of printing an hemisphere without support, but to directly print an "empty" hemisphere.

 

I build in FreeCAD such a model with a shell thickness of 1.2mm (3 times 0.4)

 

 

When Cura slice it with a wall thickness of 3lines, at the befinning there are 3 lines, like in the picture below at layer 155

 

 

Then automatically Cura adds the extra lines, while printing in the upper layers below the 314 and 444 layers

 

    

 

 

When arriving at the very top, the inside overhang is larger, so to avoid printing without support, you need to uncheck the "outer before inner wall" setting for the slicing

The picture below show the way the printing is done at layer 479 (the very top layer is 500), at the begining of the layer printing, as there are 3lines wall, Cura prints the most inner wall over the outer wall of the former layer, so there is no building "in the air"

 

 

then ....

 

Edited March 6, 2020 by JCD

[cloakfiend 995]

That all sounds great but cura should always ease in massive differences in print time per layer as i print many things most hollow some not. But i tend to design on the fly. So basically i always get the below lines near the top of the curved surface its just a pity because this could be fixed with easing the skin in thats all. Instead i have a ton more zen sanding to do. Lol

Various settings to no real removal of the visible line.

[cloakfiend 995]

Hi all again. Just thought id add that if you use 1% infil it helps a quite bit. But not perfect.

 

Still needs to be eased in in cura in my honest opinion. Anything else is a ball ache. And it would mean perfect printing. Currently top curved hollow surfaces all suffer, and if you have any detail in them you wont be able to sand it out.