Hey everyone. I’m printing a rather large part now in ABS. 150mm x 100mm x 240 mm. Seems like I’m getting cracking every inch of height the printer lays down. Printing in 0.3m layers, at 75mm/s. Bed adhesion looks great with no warping. Seems like the part is ripping itself apart. And ideas on what I might be doing wrong here? Printer is out of the way of drafts, bed is at 95c and hotend is 225c. Already ordered another KG of PLA as I got a bunch my cheap ABS is hyper-shrinky.
Thanks!
I also should say the 30 and 45 deg overhangs turned out REALLY well and infill is at 20%
The only way i can get abs to print that large without cracking is to have a heated print chamber. 45 deg C consistent through the entire print.
The easiest thing to try is put a cardboard box over the printer. Oh, its a delta. double wall refrigerator cardboard from corner to corner. With a hotter print chamber you will probably have to lower nozzle temp to keep those nice 45s.
@Daniel_Kruger ya, i was reading around and it looks like a chamber would help. i dont think i have the patience for ABS on this print. You think PLA would hold up better on a open delta?
I <3 my flexible TPU, but i have to print at 30 mm/s which would take this print almost 20 hrs to complete :S
Have you tried higher temperatures for the hot-end? ABS prints ok at lower temperatures but to get good layer adhesion you might have to crank up the temperature. I am printing my ABS parts with 245c - 255c - after realizing that at 230 I can rip the print apart with my bare hands.
@Daniel_Seiler I have only gone up to 225C. according to SEEMECNC my Rostock Max hotend can only go up to 249 C. 
can ABS from different manufactures shrink differently?
I am worried higher temps will mean more shrinkage and thus, more cracking…
Try print slower. Ithink that you are printing too fast,abs glass transition is not so sticky like pla,so abs needs more time to bond between layers.
so my print is just about finished, and i noticed the cracking stopped for the angular tapered pieces for 40 mm on the bottom and 70 mm on the top. temperatures and environment have not changed. I wonder why when its printing overhangs or angles, it doesnt lift up as much…
Go with PETG. Many benefits from ABS, but low warp of PLA. Once you use it, you will have trouble using anything else. And for large parts its amazing. The interlayer bonding is like nothing else I have used.
I have the same problem on my delta. Your cracks are small compared to how my prints rip themselves apart. PLA will fix everything! I routinely print PLA over 12 inches tall, even out in the garage at night when it is cold outside.
@Jules_Hoehn Yes PLA would probably work. Like Eric Lien said, I’ve used PET+ and it printed nicely and the print was very tough.It costs more than PLA but it’s a much better material.
Daniel K, is right the only way you can get ABS to keep from non-isotropic shrinkage, especially at that height is to decrease the rate of cooling by increasing the temp around it. Commercial printers have an oven they print in that maintains a 180-210F constant temp to allow the layers to cool slower, bond, and not shrink. A heated bed is only going to help for shorter parts.
Thanks guys! I used hot glue to fill in the gaps and minimize more cracking. I mostly want to check the fit of everything on the bike to make sure the guard doesn’t smash the windshield or front faring when turning full tilt. Once I have the part shape and size down, I will splurge on some PET. 
thanks again for the insight! Not much of an ABS fan after playing with pla/wood and flex TPU. Is that kind of the norm now?
@Jules_Hoehn Esun PETG is only $25 a KG on Amazon from interservo. I highly recommend it. I actually like it far better than PET+
@Eclsnowman thanks, I have been eyeballing that filament for a while wasn’t sure what the G or + ment for PET. What makes you like it so much? Hard to argue for the price.
G means reground recycled.
@Jules_Hoehn Glycol. It’s a modification to normal PET. http://stephen-webster.co.uk/products/petg-pet/
@Jules_Hoehn the layer bonding is the best you will ever find (short of some of the Flexible Filament like Ninjaflex. It will bend not break. Has almost no warp. No odor. I print it at 80-100mm/s on a delta regularly with zero issue at 250+C on 70C glass. Surface finish is super shiny (think like the surface of a water bottle). And flame polishes great.
Ah thanks, I guess i misread when I saw that. I hear it has a lower TG?
