Layer separating on big ABS prints

[maxamaral]

Hi, I'm trying to print some rather big ABS prints (about 15cm tall, 12 hours to print), but I'm always getting the same result of some layers in the middle getting separated, ruining the print. I've tried with colling fan, without cooling fan, and even (the red one) by closing the print area to avoid any air flow, all with the same results. This print has 2 perimeters and 10% fill.

[img]https://dl.dropboxusercontent.com/u/521 ... .22.25.jpg[/img]

Any clue on what can I do to avoid these separations? It's odd since up to about half of the height I get no issues, the happen only after that (after 6 hours printing, grrrrrr!)

Thanks a lot,

Max

[Eaglezsoar]

A little more info is needed. What temps are you using on the Hot-End?
Where do you get your filament?

[maxamaral]

Ok, there you go:

Machine: Rostock Max
ABS: SeemeCNC
Hot End Temp: 210C (If I got higher, I get bubbles)

If you need any more info, please let me know!

[lordbinky]

I think printing higher temps will help. I've printed some ABS at up to 250°C, using the E3D hotend. If you get pops and bubbles you need to dry out your filament which is inconvienent but it does make a difference.

[Eaglezsoar]

I agree with LordBinky, I print ABS at 230 degrees. You might also increase your perimeters on these large objects but I believe you need to raise your print temp.

[aehM_Key]

What's you explanation, why higher temperatures would help?

[cope413]

Optimal layer adhesion with ABS occurs somewhere between 230-250 depending on your filament.

It makes sense that it splits higher up the print because the heated bed is keeping the bottom half of the print warmer than the top half.

Just because you can extrude the filament, doesn't mean that's the temp you should be extruding at.

He's obviously able to extrude, but the layer adhesion is poor. Up the temp and give it another shot.

[aehM_Key]

But with better layer adhesion, you are not fighting the root of the problem, right?

[cope413]

It appears, from what I can see, that the problem is inter-layer adhesion with a little bit of "starved for filament" mixed in (particularly on the green one). Higher temps could/would likely fix both.

Higher temp = great interlayer adhesion = no separations

[lordbinky]

Why higher temps? The simple answer, higher temps is what solved it for me.

I think the reason is the higher temps force the layers to stick better by the new material being hot enough to remelt the surface of the layer below it.

I (eventually) followed polygonhell's advice and bumped my temps up for ABS.
http://forum.seemecnc.com/viewtopic.php?f=37&t=2447

[aehM_Key]

Yes, it could minimize or maybe solve the problem in some cases, but the real issue is warping. High forces occur due to the shrinking of the ABS.
You don't have much room to play with the temperature, if you also take for example bridging and stringing into account. So I think the only real solution could be a heated chamber.

[cope413]

Thankfully, it's not the only answer. And the reason I know it isn't, is because I printed this out of ABS...

Single walled and 25cm tall.

Yes, it did warp slightly at the top, but had it been more than single-walled, it would have been fine.

85C bed with glue-stick and 8mm brim. 255C print temp with 80mm/s print speed - spiral vase setting in Slic3r.

Matterhackers ABS

Pretty happy with it.

[Flateric]

preventing drafts of anykind around your printer will help alot too. Or even better try to enclose your print some. Even just a little, will help prevent the temperature difference between layers on really large prints.

[bsdtgr]

I have found with my larger prints, when a strong breeze hits them it will cause a split in my layers. I have also seen a lot of people online using filament dusters to clean the filament as it is being used. As for the bubbling at 210, my guess would be moisture in your filament. If you store filament in a sealed container with silica packets it will help keep your filament nice and dry.