ABS print cracks

Hi to every one. i have ormerod 2 and i usually printing with ABS. My problem is when i print large objects the print output cracks in some portion. First i thought my hot end temp was just to low so i increased it to 250Deg and bed at 120deg. But the same results see attached pics. By the way it was sliced by cura.

What does your hotend look like? If you cool ABS prints too much, the tension inside these parts will cause warping and can cause the layers to split.

It is extremely difficult to prevent tall walls or blocks splitting. It probably needs a temperature controlled enclosed build space to eliminate it completely. As said, use no cooling at all (modify the hotend so there is no cooling air blowing onto the nozzle), and ensure there are no draughts. If it is your own design, avoid sharp outside corners, and if you can, put a thickish column or teardrop at the ends of thin walls to prevent the wall ending with a sharp corner. I have made an ad-hoc printer enclosure by putting a bin-bag over the printer, but you have to make sure the temperature doesn't get too high inside.

The splits you show in your photographs are nothing much to worry about - I've repaired far worse than those. Simply drip some acetone into the cracks (or briefly dip the whole print in acetone), and clamp the splits closed. On small prints the splits could be pressed closed with some elastic bands, or even held closed in your fingers for 15 minutes or so. Larger prints might need weights, G-clamps or some other way of closing the splits. The acetone creates a chemical weld that will be stronger than regular layer bonds within a couple of hours or so, and often makes an invisible repair (or just a thin slightly darker line).

Bigger splits can also be repaired in the same way, but you will end up with a print that is significantly warped.

Dave

Thank you for your replys, i alrady removed the fan duct and i temporarily enclosed the the print bed with card board. I have a good results now. thank you.