Hi, there are these irregularities at the bottom of the print which I think might be tiny holes.
It’s a 45 degree overhang and it is printed in vase mode. I printed it with a 0.8 nozzle using 0.4 layer height and 1.2mm width. Nozzle temperature was 220 degrees and print speed was 16 mm/s. The part fan speed was 100% and the aux fan was turned off. Also the exhaust fan speed is 10%.
Was wondering if anyone had any suggestions.
Here’s some godawful MS Paint. When your line width is greater than your nozzle aperture, you are basically doing a “super squish” but if there’s air under… squish wont be even.
When the nozzle is extruding, it comes out like a cylindrical log. That log has to hit something below in order to squish out wider. The blue hash marks show the side of that log. That side of the filament is overhung strongly, and is gonna slip down and round over a bit, and not fully create the max width expected on the outside.
Higher line width of the outer wall means your model can tolerate less overhang angle. Vase is all outer wall, so, yknow.
Maybe try soaking it in all the fan you can give it, make it crisp up earlier.
Thank you, and I was thinking that increasing the line width was supposed to help overhangs.
An increased nozzle size/layer height ratio helps for overhangs.
Basically when you reduce the layer height, the side step becomes smaller per layer and therefore making more of the layer rest on the previous layer.
Reducing the layer height too much will introduce the same effect as @Bullocks is describing, where the material squishes more outwards because there is less resistance (pressure) there.
An increased line width helps to press a layer stronger onto the previous one. Thats also why the 1st layer width is usually larger to get better adhesion to the build plate. But 150% of nozzle diameter is too much for large overhangs.
Thank you. I will first try printing with reduced layer height by half and if that doesn’t work then try printing it not in vase mode, with two 0.8 walls.
So I solved it by going the other way lol. Printing it with 0.56mm height and 2mm width solves that problem BUT now the curved part in the mid section which didn’t have any issues before has deformations just as the curvature starts, then it gets better . Doesn’t make sense, shouldn’t it be printing easier after that overhang? Also I increased the Aux fan to 100%.
Overhang part:
Have you measured the diameter of the flat face on the nozzle tip? Afaik that is approximately 2x the nozzle diameter. With 2.0 line width you are already over that limit.
I didn’t but according to this post: https://forum.bambulab.com/t/why-can-a-0-4mm-nozzle-print-0-8mm/37142/4?u=tncrdn it should be 2.0 also adding the semicircle on each side.
I’m also wondering how you would approach printing this. I tried printing without vase mode using 2 walls of 0.82mm, tried it both with inner/outer because of the overhang and outer/inner, even thought the inner/outer gave me a better result the surface quality still wasn’t as good as vase mode.
And printing 0.8mm wide in vase mode is not good enough for my purpose, it should at least be 1.2.
I really wish Bambu released nozzles bigger than 0.8 but I guess that is never going to happen.
Just measured my 0.8mm nozzle and the max diameter is closer to 1.4 than to 2.0mm
So with 2mm line width, the filament is oozing over the outside of the nozzle.
Yes, if its total width is 1.4 and layer height is 0.80, you can only print 1.8 mm wide lines with quality. 1.4 might well be correct, it’s very hard to measure the nozzle flat size as the nozzle is conical. The “2x bore” was the best I could estimate (with X1C hotends, all sizes) back when I explored this.
Come to think of it, someone said it’s 0.6 mm (so nozzle flat size is 0.8+0.6), which actually fits your measurement perfectly. If it’s 0.6 mm regardless of bore, we can print wider lines with 0.4 (1.2 mm) and thinner lines with 0.8 (1.8 mm). For a 0.6 nozzle, the “2x bore” holds and you can print 1.5 mm wide lines.
0.56 height and 1.2 or 1.6 width gave me the best result. I don’t know why but 0.56 printed much better than 0.4
