Cool environmental conditions are the single biggest contributor to ABS delamination. Delamination or edge/corner cracking is caused by warping stresses when the first layer adhesion is stronger than the interlayer bonding. Or it happens when the heated build plate allows a strong non-warping foundation to be built until the print is too tall to be adequately warmed by the plate. In either case, the corners of the first layer can't lift, so the print cracks elsewhere to relieve the stress.
All ABS warping stress, in turn, is caused by the repeated thermal contraction of the fresh plastic layer at the top of the print. The FDM process sticks hot, expanded plastic onto cool, contracted plastic. When the new layer cools, it tries to contract, but it's stuck to a layer that is already fully cooled/contracted. This generates a large shear stress between the two layers. The accumulation of those shear stresses over many consecutive layers generates a large-scale bending force on the entire print. That's what causes both warping and delamination.
The less the previous layer cools below the glass point of the plastic, the less thermal contraction it experiences before the next layer goes down, and therefore the less warping stress will accumulate as the next layer cools.
Environment temp is the biggest thing you can control:
- If your printer's environment is below 35C, you probably shouldn't even bother printing ABS.
- A 50C environment is significantly better and will have minimal problems with warping and delamination. This is within the ambient temp ratings of most motors and electronics. Air-cooled extruders can typically extrude ABS reliably up to about 60C ambient, at which point they may be prone to clogging. And don't forget about plastic structural parts in your printer.
- Industrial ABS printers with heated build chambers print ABS in a 75-85C environment, with lots of airflow. In terms of cooling regimes, ABS in an 80C chamber acts very similar to PLA in a room-temp environment. No warping, but lots of airflow required for good detail.
Printing ABS at a higher nozzle temperature (say 240-250C) will also improve layer adhesion so delamination is less likely to occur. The same warping stresses will be there, but the layer bonding may be stronger than the internal stresses in the part so it survives printing.
