Why does my PLA start to curl after a few layers?

Filament
1

Hey all, I recently became the proud owner of a Lulzbot Mini. This is my first 3D printer. I’ve been a lurker here on the forum for a couple of weeks soaking up the useful stories and advice you all have to offer. So far, the experience has been a lot of fun, and I have completed some cool prints.

I have noticed that when printing with PLA my prints tend to curl on some of the edges. This is most noticeable when the print reaches layers that overhang the outer shell of the print, and varies from minor curl to severe curl depending on the amount of overhang. Usually my prints finish when this happens, but the areas where curling occurred are of a noticeably lower quality.

Why does this happen? What can I do to minimize the curl?

I’ve attached some photos of a print that is currently in the works. Here are the print details:

Model: http://www.thingiverse.com/thing:607518
Filament: 3mm Matterhackers Light Blue PLA
Slicer: Lulzbot Cura
Settings: Built-in Quickprint profile for “high quality” PLA

Thanks in advance for any advice you guys can give!

IMG_20150701_091556.jpg
IMG_20150701_091556.jpg3120×4160 2.36 MB

IMG_20150701_091518.jpg
IMG_20150701_091518.jpg3120×4160 3.22 MB

2

I have never had PLA do that. I have used several brands but not MH. Are you sure it is PLA? ABS is notorious for curling like that.

Drop a piece of it in some acetone and see if it dissolves over the course of a few hours. If it does, you probably have a mis-marked spool of ABS.

You might also try giving your print bed a vigorous wipe down with isopropyl alcohol on a terrycloth rag.

3

Ah, okay, so PLA does not dissolve in acetone? Unfortunately, I don’t have any acetone on hand. I’ll pick some up and try it out.

Thanks for the advice!

4

My print finished! Overall it came out really good. I attached a finished shot, and another one to show one of the lower-quality spots where there was a lot of curling during the print.

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IMG_20150701_114549.jpg3120×4160 2.14 MB

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IMG_20150701_114639.jpg3120×4160 2.29 MB

5

PLA absorbs heat really well. So much so that when printing items with overhangs, any additional cooling you can provide will help tremendously. Once you are comfortable with Cura, you can use expert settings, bring in the profile you want to use, and change the fan speed settings. For now, pointing a desktop fan at the print will help with all your overhangs.

6

Orias: thanks for the tip! I have tried a few prints using expert settings, mostly just tweaking some of the default Cura profiles provided on the Lulzbot.com support site. However, I have not tried changing the fan speed settings. Are there any considerations I should make when tweaking fan speed? Put another way: is there a reason why I shouldn’t crank it up as high as it can go?

Tangentially: would it make a difference to lower the print temperature, or would that create other problems?

I haven’t had a chance to try dissolving the filament in acetone yet. However, I tried a break test to see if the filament is bendy (which I understand to be a property exhibited by ABS), or if it snaps into pieces (I am told this would imply that it is probably PLA). It snapped, so I’m a little more confident that the PLA is actually PLA.

7

The quick way to see the difference would be to just point a desktop fan at the printer while it’s printing. Then once you’re comfortable with loading profiles in expert mode, experiment with the fan speeds.