Prevent Cura from ignoring very small details

[krikru 1]

I found this incredibly detailed model of the Eiffel tower: https://thangs.com/Roboninja/Eiffel-Tower-15733

 

My problem is with using this model in Cura, though, is even if I scale it up to cover the entire height of the build volume (which is 250 mm for Ender-3 which I use), choose a 0.2 mm nozzle, use 0.06 mm layer height and enable Print Thin Walls, the smallest details in this print are still too small to be printed, and as a result, Cura just ignores them, as can be seen in the attached image. This is not good, as they are an important part of the model. They can be made thicker, but they should not be made any thinner or removed.

 

 

Is there a way to make Cura print (generate gcode for) these details? Maybe make them thicker somehow in order to prevent Cura from ignoring them?

Edited July 8, 2021 by krikru

[GregValiant 1,492]

Unfortunately scaling things down has that effect.  That model is seriously scaled down from life size so, yes, it is going to lose a lot of definition.  In any software, you can scale X and/or Y and/or Z but you can't scale part-of-a-part.  It's an all-or-nothing deal.

There really isn't anything you can do unless you are willing to jump through some hoops.  You can try scaling it up so the base is 225 x 225 then increase the height of your build plate to 550.  Add a support blocker as a "cutting mesh" and print the model in sections and glue the sections together.  It will end up about 500mm tall.

The model itself has problems (this is the most errors I've seen in an STL):

-> Analysed your file:
--> 16 Naked edges
--> 4 Planar holes
--> 0 Non-planar holes
--> 7043 Non-manifold edges
--> 9587 Inverted faces
--> 0 Degenerate faces
--> 2856 Duplicate faces
--> 0 Disjoint shells

 

This is with a .4 nozzle and no support.  It does look like all the features sliced.  This is scaled 1617%.

 

Same model with support.  That's a boat load of support.  48 hour print and 250 meters of 1.75 filament and it's just the bottom section.  I don't really see a way to print it without support and I don't see a way to print it with support because it's so delicate it won't hold up to support removal.

I'm going to call this unprintable but you can give it a shot if you want.  I did generate the gcode file and it was 117mb and 4,046,430 lines of gcode - just for this bottom section.

 

Edited July 9, 2021 by GregValiant

[krikru 1]

Thanks for your analysis of the model! It seems like maybe I should try to print some less detailed model in that case. By the way, how did you divide the model into segments? Can that be done in Cura or did you use some external software?

[GregValiant 1,492]

That big gray box on top is a support blocker.  It can have different properties and be moved and scaled like any model.  In this case I used the button above the support blocker tool "per model settings" and selected "modify settings for overlaps" and then set it to a "cutting mesh" with 0 wall count, 0 top and bottom count, 0 infill, and with support disabled.  It becomes a Mesh Modifier and since there isn't anything left to print of the overlapped area, it cuts the model off there.

For the top, I would have sunk the model into the base plate and moved the block to an appropriate position.

 

That is a really nice model it just isn't appropriate for FDM printing at a reasonable scale.  The flat "floors" that occur up the top of my slice of the model would all need support and that support would have to be removed.  Maybe with PVA it would be doable but it would still be very difficult.

[krikru 1]

Oh, modify settings for overlaps seems so useful! I guess it can also be used for reinforcing certain parts of a model that otherwise are prone to breaking. Thanks for the explanation!

 

I guess you are right about supports being necessary but at the same time are required in massive amounts and prone to breaking many of the thin details, unless you print them with some soluble filament (unfortunately not possible on my stock Ender-3).