Feature request: hilbert curve top/bottom pattern

[bzed]

hi,

I know that hilbert curves as top/bottom pattern result in an insane amount of printer movements, but the result just looks great. please implement it like slic3r does :)

https://imgur.com/gallery/SLdeM

thanks,
bernd

[Ghostkeeper]

You like it just for its aesthetics, do you? It doesn't seem useful in any way and would certainly give quite some trouble with overhang above infill...

You could also use Cross infill at 100% for a door such as that, and remove the top skin so that the infill gets exposed.

[Ghostkeeper]

Our project manager just removed this feature from our planning because it's older than 12 weeks.

[BagelOrb]

It might be an option at some point in time, because it might be a side product of the research I am currently doing at Delft Technical University.

Ultimaker won't spend time on this, though.

[BagelOrb]

Actually I already implemented it, but it will take a while for it to actually appear as an infill option in Cura.

[zarthcode]

Just wanted to chime in, I have found that using the hilbert curve is superior to rectangular for the bottom infill for my particular setup when using PETG with thin layer heights.

[mbartlett21]

@BagelOrb When will this be in Cura?

[BagelOrb]

Well. I've implemented the Hilbert curve itself, but not as an infill option directly.

I do see how the Hilbert curve might work well for 100% filling with minimal working. It should work better than the CrossFill pattern, since CrossFill doesn't support 100% dense filling.

However I really don't have the time for this. Perhaps you can find somebody in the Cura team or somebody from outside who would be willing to make the final step from my implementation, which is at https://github.com/Ultimaker/CuraEngine/tree/fractal_dithering

Specifically the file https://github.com/Ultimaker/CuraEngine/blob/fractal_dithering/src/infill/SquareSubdiv.h

[MRAAGH]

You like it just for its aesthetics, do you? It doesn't seem useful in any way and would certainly give quite some trouble with overhang above infill...

The hilbert curve is very useful for the initial layer because it localizes heat. Neighboring lines (which are all melted simultaneously) merge together, resulting in reliable adhesion even when the nozzle height is not calibrated perfectly.

Virtually any other initial layer pattern is more sensitive to calibration: whenever a fresh line is printed next to a non-melted existing line, the imperfections of the existing line carry over to the new one.

[BagelOrb]

Interesting perspective. Why do you think that molten lines absorb imperfections better? Overextrusion is overextrusion regardless. If the lines next to the one being printed is still molten then that line will bulge upward, causing the same type of problems, right?

Have you prototyped any of this? Or is it purely theoretical at this point?

[MRAAGH]

Printed with lines pattern:

Printed with Hilbert curve, on same bed, same filament and temperatures (Prusa Slic3r):

1. The first print has artifacts on the initial layer. An artifact begins where the bed is higher (I print on glass without auto leveling). If printing long parallel lines, the artifact is emphasized on each subsequent line. What you see is a minor example (I don't have any better ones on me right now). Typically, I end up with an ugly triangular pattern on the underside of the print. Plus a chaotic surface which can cause further complications when printing the second layer.

2. On the first image, notice how the printing lines are very visible? They did not merge together because they were not melted at the same time. Meanwhile, the second print is so smooth you can even see my fingerprint on it. Clearly, such coverage means more contact with the bed, thus better adhesion.

[BagelOrb]

Very interesting stuff. I wouldn't consider it to be proven yet, though. There are multiple parameters which can influence this.

How many prints did you do with the Hilbert pattern? Does some other slicer offer it?

The Hilbert pattern has a lot of corners, which means that it will be printed at a relatively low speed. Have you compared against just turning the bottom layer speed down on the lines pattern?