Weird layer lines due to surface mode

[stenkluts 2]

Hi Guys,

 

I'm trying to slice an incredible big print with 10mm nozzle and 3mm layer height. The problem is that during printing i see that the layers are not even in some parts. some are wider than others. first i thought it was the machine, been at it for a week now and checked everything. So i turned to the slicer. i found that when i turn surface mode 'on' (surface) it produces a nice clean print, but i cant do infill (not even custom infill). Does anybody know another way to solve or use this with (custom)infill?

 

You can see it clearly in the pictures, i didnt move the camera, just re-sliced.

The object is a .OBJ bc of the resolution, with STL it does an even worse job.

 

Hoping someone can help me out!

Kind Regards,

 

Surface mode: Surface

 

 

Surface mode: Normal (defoult)

[Slashee_the_Cow 382]

If you could share the Cura project file (.3mf, in Cura get it set up then go to File > Save Project) that would really help. It looks like the sort of thing that's almost impossible to diagnose based on a couple of screenshots.

 

If the file is too big to post to the forum, it's probably best if you upload it to a cloud storage service like Google Drive (or whatever you use, if you already use one) and post a link.

[stenkluts 2]

Unfortunately i cant share the .3mf file as the model i use is sensitive. I tried to recreate the problem with another model but i couldnt. so it's probably a foult in the (smoothness of) the model. 

 

I do think its still weird the slicing tolerance of the 'Surface mode' makes such a huge difference in smoothing out polygons.

[Slashee_the_Cow 382]

A screenshot from an angle showing a cross section with both the outer wall (with errors) and what's inside could help. Unfortunately without having a project file to mess with numbers in until we get the desired result it's a lot harder to troubleshoot. Here's some ideas, anyway:

• Have you tried setting Special Modes > Surface Mode to Both to see what result that gives you?
• Make sure Mesh Fixes > Maximum Resolution is fairly low (I usually use 0.1mm, but feel free to go nuts and go to 0.001mm or something if you want) - assuming your printer can handle it, it's there because if you try to be too accurate with some printers it produces too many instructions and the printer can't keep up, and I don't know what whatever you're working with can handle.
• Set Walls > Minimum Wall Line Width to whatever the thinnest your nozzle/printer can handle is. I can tell you what it is for a 0.4mm nozzle easily... never used a 10mm nozzle. If you apply the same guideline for line width (60-150% of nozzle diameter) then your minimum width would be 6mm. Cura isn't really designed to handle things at that scale (it can be hard to get a 1mm nozzle print to come out nicely) but that doesn't mean it can't do it (theory is the same, maths are just bigger numbers).
• You could try setting Walls > Outer Wall Inset in a little bit ("a little bit" depending on your line width, but if I do it I usually go by a quarter of my line width - too high and you'll just get overextrusion messing things up) but obviously this affects the dimensional accuracy of the model... I don't know if you can perfectly counteract that by setting a horizontal expansion of the same size or not.
• Try playing with the different settings for Experimental > Slicing Tolerance and see if any of them make a difference.
• Based on the way the lines are oriented, I'm guessing this wouldn't help, but while we're trying stuff: open the Marketplace at the top right, find the plugin called "Arc Welder" and install it. Restart it, and then enable it at Special Modes > Arc Welder. It converts circles from a bunch of short straight lines like they usually are into G2/G3 circular moves (if your printer can handle those).

It's not necessarily unusual that setting Surface Mode to Surface smooths it out. Surface makes Cura generate a cross section of the model at each layer and then only uses closed loops to generate a surface. This means that the outer walls will never be affected by any other part of the model because there are no other parts to affect it.

 

There's still the possibility that the model file isn't at fault just because you can't replicate it on another. See if you can make sure your model file is valid (if you're using Windows, Microsoft's "3D Builder" app is actually really great at detecting and fixing broken models).

[stenkluts 2]

Thank you for the extensive reply @Slashee_the_Cow.

 

The model is a solid one, printed with just 1 outer layer.

I use 2 erasers to put 2 single lines of custom infill, but the problem is there with and without that infill.

 

- Special modes, 'Normal' gives the same result as 'Both'

- Mesh fixes, i played alot with this setting earlier. tried it again and very high and very low and everything in between does not make a difference.

- Set walls minimum line widht, tried to play with this but also no change.

- Outer inset didnt change anything as this is the only wall.

- Experimental, slicing tolerance, didnt change anything. (also played around with Minimum polygon circumference)

- Arc Welder, i have used and tried this before. But our post processor doesnt take it well so i cant use arc welder. Also the screenshot are from straight lines. 

 

Handy to know how surface mode slices the part, that way of slicing should always be an option (but then with infill ofc haha)

 

If you have any other ideas let me know, in the meantime i will try and keep on fiddling with it.

Again, thank you for your extensive information.

[Slashee_the_Cow 382]

It's a bit of a stretch, but there is always the "manual" (read: very tedious 🙄) way of doing it: slice it once with the surface mode to set to surface, and one with it set to normal, save them as separate files. Load both gcode files and for each layer individually (hence the tedious part), copy everything which isn't an outer wall (don't worry, there's comments in the gcode files saying what kind of feature it's working on) and paste it after the wall in the gcode file from surface mode. Hence how tedious depends on how many layers you've got. Open your combined gcode file in Cura first to see if the preview looks good (it's not always great at displaying files which have been edited by hand, but if you do it layer by layer it should manage it).

 

If I can think of any more sane ideas I'll be sure to let you know 🙂

[stenkluts 2]

@Slashee_the_Cow Haha i actually like this idea, Maybe i can write up a python script for it. Once we have the perfect gcode, we will be loading it in hundreds of time. i will discuss this with my engineer and keep you updated on here! Today we are actually starting a print that is 5.8m long, 2.4m wide and 1.5 high of this model. if it succeeds i will share pictures.

[stenkluts 2]

@Slashee_the_Cow i have tried it on cura 4.13.1 and played around with the resolution settings. Looking at the slicer it looks nice and clean, with the custom infill. Surface mode set to Normal. I do still have to test it on the big printer, i will do tomorrow.