ABS splitting by unknown force

[gajtguy]

I have this model where I combined This model and a custom speaker shelf. I've tried to print this twice now and the model splits at the lower portion of the circle, right where all of those air channels are. I understand that is the 'weak area', but I fail to understand what is pulling UP on the most recently printed section so that it splits from the older base portion? To add to that, the split is more dramatic the further you are from the shelf portion. Almost like there is some hidden cantilever hidden in the area where the shelf supports meet the circle.

Any ideas as to why this is happening?

Printing on a Rostock V2, with ABS. Bed=90, Nozzle=215. Spliced with Cura 15.04.6. Bed adhesion=ABS Slurry .5Nozzle 1.75 SeeMeCNC ABS Spool

Thanks for the feedback

[gajtguy]

Print #2 went much better. But still split in a couple of places.

My house temp in that room is 74 degrees. Is this just a cooling issue that an enclosure might fix? I dont print many long prints like this (7hrs)

[Xenocrates]

Yes, this is cracking due to warping, which can be fixed and mitigated with a heated enclosure. For example, on my Max, I would sometime see a part split ~30% of the way through (large domed part, light infill, so once it started it kept going) before I put a heated enclosure on it. Recently as the temperatures have dropped, if I get splitting, it usually occurs when I open the enclosure door (Do allow them to cool gradually if the outside temp is less than ~24C)

An enclosure to trap heat is a good starting point, but active heating and control is even better.

[gajtguy]

Thank you. I'll have to bone up on the quickest most cost effective enclosure system to implement.

[geneb]

I wrapped Blue Max in a couple of layers of yellow canvas. I used document clips to keep in place. Looks like hell, but works pretty well.

g.

[Mac The Knife]

Printing ABS at 215 C is kinda low? I'd crank the heat up to 240, at least. The layer you are putting down has to be hot enough to bring the layer below it up to temperature to fuse together.

[gajtguy]

Oh. well thats easy to change. I think there was a previous post that caused me to reduce the temp to 215. You have to be a 'tweeker' with this hobby dont you?

[nebbian]

You really do have to tweak tweak, then tweak some more. And once you've got everything dialled in you go to print a different model and it's back to the tweak cycle.

Things that have helped me get better layer adhesion:
1) Raise the temperature. I set my nozzle to about 255 on ABS.
2) Increase extrusion width. With a 0.5mm nozzle use an extrusion width of 0.65 or 0.7mm. This gives you more 'squish' and forces the layers to bond better.
3) Turn your layer fan on (but at a very low value, so that it's just ticking over).
4) Use an enclosure. Even some cardboard duct taped around the sides will help. It does help if you can get it as airtight as possible, especially towards the top.