ABS Woes - Need Assistance (pics attached)

Help with printing with specific plastic filaments.
billyd
Posts: 234
Joined: Thu Mar 12, 2015 11:06 pm

Re: ABS Woes - Need Assistance (pics attached)

Post by billyd » Sun Mar 06, 2016 7:07 pm

Delamination in ABS is mostly caused by too low of an extruder temperature. You can go pretty high with ABS. Even up to 260. The only downside is with some colors you can start to discolor or de-gloss them. An enclosure can help a little with delamination because an enclosure will lead to lower thermal stresses so the bond between layers can be lower and still not crack. But increasing the extruder temp will improve the bond between layers and allow for more thermal stresses before cracks occur, than it would with a cooler extruder.

When you are printing things like the cat, or other small objects out of ABS, you have to let the part cool down before putting down the next layer. With small objects and details in ABS, heat is no longer a friend but an enemy. Slower print speeds can help if you don't have to go too slow. But if you slow down too much the part will overheat because of the slow extruder lol. I find with really small details you need to print multiple objects, it's the easiest and best solution imo. Try printing 3 or 4 cats instead of changing print speeds, and be sure to turn off island optimization in your slicer.

Printing overhangs in ABS such as when a wall that curves or angles away from the support beneath, I find letting each layer cool (just like with small objects) helps a lot too. So again, the old standby for me is to print multiple parts, or if the part is big, slow the print speed way down. You can set up multiple processes in the slicer to do the areas like this slowly, and then speed back up for the rest of the model.

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hemocyanin
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Location: Puget Sound

Re: ABS Woes - Need Assistance (pics attached)

Post by hemocyanin » Tue Mar 08, 2016 2:43 am

PeterT wrote:Well, I would start by saying; nothing like jumping into the deep end!
My thought exactly. ;-) Even the cat is a deceptively difficult shape.

Focusing on the fat cat. First, I've only bought one spool of IC3D ABS (in black) and I found that it was much more gooey than eSun's ABS. I'm not saying for certain that is your problem, but when I look at the underside of the cat, I can imagine that the plastic in that area was still soft and moving around underneath the printhead, especially because that area has such a narrow diameter in those layers. To make matters worse, if your filament is sort of extra gooey, the nozzle will pick up a residue and become sticky and increase the amount those little nubs wobble around.

I'm printing a test of the cat right now in PETG, which is gooier than ABS. Watching the nozzle run over the feet and head low layers, I can see the nubs that are building up wobbling all over the place. I'm stopping it -- it's already looking terrible.

Getting the bottom right is a matter of letting it harden before you put on another layer, otherwise it'll just wobble into ugliness. So for my second try, I've dropped down from 248 to 240 for my nozzle temperature, and from 85 to 75 for my bed temperature. Mind you this is with PETG. With ABS, maybe drop the bed to 100, or even 95, and the nozzle to 235.

In Cura, you can set a minimum layer time which may help. It is in expert settings, advanced tab, under "Cool" heading. I bumped that up to 60 seconds minimum per layer.

I'm using a lot of fan in my unheated garage with PETG because it seems to like the cold. The conventional wisdom with ABS is that you want to use as little cooling as possible because it doesn't like cold. With too much cooling on ABS, you get layers splitting like in the house model you made. However, for a small piece like the cat, you might actually want to give cooling a try. It probably is small enough to avoid delamination, but getting those bottom layers really solid when they are just nubs so that they don't wobble around is going to be key. It may take some fiddling to get the balance right between having the first few millimeters solidify, and the larger areas not delaminating.

Also, my first aborted bad version had 4 shell layers. My second more successful one only two layers. I think you want to have the nozzle on the edge of those nubs as little as possible. Anyway, it isn't perfect (there is still some roughness on the underside) and more fiddling would make it better, but this is my result focusing on what is happening with the nubs (bottom of the spheres) -- I cut off the round pedestal so it would be easier to see the bottom. Printed at 0.2 mm layer height:
IMG_0628.JPG
IMG_0627.JPG
IMG_0626.JPG

altertalk
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Joined: Sat Aug 27, 2016 8:17 am
Location: Williamsburg, VA

Re: ABS Woes - Need Assistance (pics attached)

Post by altertalk » Fri May 12, 2017 6:11 am

I see the exact same issue with PLA, but not as bad with Alloy 910. Has the Lulzbot team changed or created any specific Cura profiles to print sphere type objects? Being an intermediate in this technology, I'm finding all sorts of shrinkage issues I did not expect to see.

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