What went wrong?

[Escarjoe]

I'm pretty new to 3D printing. I'm using an Ultimaker 2+ with PLA, a 4 mm nozzle, and the presets in Cura. I did switch it to the "fast" preset and I tried to print without supports. Everything seemed to be going fine when I left for the night, but in the morning the print was on the floor and there was a loose pile of extrusion on the bed of the printer. The nozzle is probably clogged now. This was a large size print, but I thought it was within the acceptable size range for the printer. The "arches" at the top were supposed to connect. I knew making these bridges might be a problem, but I kept the angles at 45 degrees thinking that would be gradual enough. Maybe the narrow pillars couldn't support the weight? Any ideas about what went wrong? Image attached. Thanks for your help.

[noiseboy72]

What can happen on very tall prints is that the print head touches the previous layer, causing the object to move and eventually detach from the bed.

for that sort of structure, I would personally break the object down into smaller sections and then reassemble post print.

[curious aardvark]

insufficient stick to the printbed.
And too fast a print mode.
Bear in mind that tall thin prints will pick up the printers vibrations and wobble, this obviously disrupts clean printing and will cause blobs and misalignments and cause te print head to catch on the print. the faster the print head moves the harder it will hit the print and the greater the likelyhood of knocking it loose.

Second NEVER use presets on slicers.
They are universally too fast - I've never yet seen a preset setting on a slicer I'd consider correct.
Try to have the print and travel speeds either the same or close to each other, this cuts down on shake. having the printhead constantly speeding up and slowing own, makes the printer shake and makes the model shake. Also for tall thin prints you want a slower speed anyway, allowing more time for each layer and cutting down on printing on wobbling parts.

Also for that long a print you had very little material touching the printbed. Consider adding a wide brim. I personally go for brims rather than rafts as rafts on long prints are a pita to remove. whereas a brim can be easily cut or snapped off.

So in essence:
1) print slower
2) stick it better to the bed
3) As noiseboy said - consider breaking it down in to smaller chunks.

[Escarjoe]

Thanks noiseboy72. I considered printing it in pieces and gluing it together, but for some reason I was nervous about trying that. I guess I should get over that.

[Escarjoe]

Thanks for your response curious aardvark. I don't know why I was trying to print fast. I need to adjust my expectations. I will definitely try your tip of matching print and travel speed, and I will use a brim next time. I didn't realize that there was not enough of a base. I was probably too ambitious with this model. I'll go back to printing smaller objects.

[curious aardvark]

The thing to remember is that a successful print that take 6 hours, is more cost effective than two failed prints that should have taken 3 hours :-)

Also on a large print with little surface area, make sure the first layer goes down very slowly for maximum adhesion.
10% of printspeed is what I usually go for.