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Strange print issue

Posted by Cougar281 
Strange print issue
January 12, 2018 08:31PM
So far, I've printed pretty much one thing at a time, and so far, my prints have pretty much all come out decent. Maybe not 100% perfect, but definitely functional.

But today, I had my first print snarl-up. I was trying to print this (nine of them at once on the plate), the way the author printed them (upside down), and after the first handful of layers were down and looking good, I left it be and ate dinner and put my daughter to bed. When I came back to it, it was a snarled up mess glued to the nozzle.

I then printed one by itself, and that printed fine, although it was a bit small for the magnets I have, so I scaled it up and printed again. I did a handful of test prints, and in doing so while watching it, I found that it lays down the first layer fine, it continues to lay everything down fine until some point after it gets to the top of the shaft and starts to expand out. I noticed that at some point after it does that, the outer wall appears to 'curl up' to where it ends up at last .5mm higher than the bottom of the nozzle. I suspect that's why when printing the nine of them, it snarled up - as long as I'm only printing the one, the nozzle stays within the bounds of this 'lip' and it never causes issues. It seems like it doesn't complete cooling right away since as the nozzle moves around it, the material pushes out slightly. When printing one, it works itself out and by the end, it prints fine, but when printing the nine of them, I suspect enough time passed from one to the next to allow the material to cool and cease to be pliable, and the print head then knocked them over one by one and sent the whole print sideways.

I've tried slowing the print down and reducing the flow (Although the display on the printer doesn't seem to reflect the reduced flow rate specified by Cura on the LCD), but nothing seems to change it.

Any ideas why, seemingly only when the print starts to increase in width, it starts to create this 'lip' that essentially ends up straightening itself out by the end?
Re: Strange print issue
January 12, 2018 10:34PM
I think that the 'curl up', the overhang is too steep. As a result, the layer is almost printing in mid air. Cura 3.1 has a hidden setting "Infill before walls". Un hide it and try the setting. In theory, by printing the infill first, it gives support structure, something for the filament to attach to.

Another thought is to spread out (space out ) the models across the build platform and try Special Modes -> Print Sequence -> One at a time. This may also be hidden and will need to be exposed via settings

Also, Fan on 100% and slow printing. I use 7 seconds for minimum layer time.

I have not used the first 2 settings yet.

EDIT: What temperature are you printing at? Material? Layer Height?

Edited 1 time(s). Last edit at 01/12/2018 10:44PM by mjf55.
Re: Strange print issue
January 13, 2018 12:33PM
Thanks, I'm using Cura 3.1 so I'll look for those settings and give them a shot.

I'm printing with PLA at 210, 60 bed temp and .1 layer height. Speed 40 with a wall speed of 20.

Unfortunately, I don't have a cooling fan for the print (just the one for the throats heat breaks). I'm going to have to try to find some kind of duct setup that'll work with my carriage and print heads, or some year figure out how to use one of the 3D programs like Fusion 360 or similar and design one.

Edited 3 time(s). Last edit at 01/14/2018 06:38PM by Cougar281.
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