Good and bad print in one!
Hi!
Very new to the world of 3d printing and recently tried to print a sphere within a square! It worked fairly well but the finish to the underside of the object (from the base plate) is very poor, but as it prints further towards the top part of the object it looks amazing. I have attached a couple of images, one showing the rough part of the print and the other the smooth part.
Would anyone know why this happened?
Thanks in advance
Fred
Re: Good and bad print in one!
Very new myself (my printer is running since Sunday afternoon, and I've already printed two objects that weren't on the included SD card 😀 ), but I think you are running into two things here:
- your bottom layer may be too far away from the printing surface, see the Z life adjust thread here: https://shop.prusa3d.com/forum/-f6/life-adjust-z-my-way-t2981.html , you should have a smooth surface with no visible structure on those parts where the model touches the printing surface (or the negative impression of the surface, if you use a structured surface like the powdercoated sheet)
- the model has some overhangs, which the printer can't always cope with, i.e. the printer (usualy) needs something to lay the filament on to, it can't print on thin air. It's apparently possible to print on thin air up to some degree between existing support points (called "bridging"), but I don't know the limits of that yet (except the general guideline that 45° should be safe...)
For example, look at the Benchy in this thread https://shop.prusa3d.com/forum/assembly-and-first-prints-troubleshooting-f62/seriously-impressed-with-what-the-mk3-can-do-when--t25141.html , especially the underside, and compare it to yours.
Re: Good and bad print in one!
You've almost got it. Bridging is used when the printer can span (bridge) a thin strand of filament between 2 surfaces. There's something to adhere to on both ends. An overhang is when there is only one side supported. The printed filament extends past any support and there's nothing to bridge to on the other side. You get that "printing in air" effect with rounded strands of filament, which accounts for the rough undersides.
[...] It's apparently possible to print on thin air up to some degree between existing support points (called "bridging"), but I don't know the limits of that yet (except the general guideline that 45° should be safe...)
You can try using support, but unless you're using dissolvable supports, you have to leave a gap between support and the print, so you're still going to get roughness at extreme angles. As the print moves up a curved surface, the extrusions stack more neatly on top of each other, so you get a better finish.
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