[Part start cracking while printing.]

As far as I understood, the basic reason is that ABS requires a very hot temperature to melt and fuse well. The new layers tend to cool down too fast, thus without proper fusing to the previous layers. You need to keep the temperature of the old layers way up too: close the front of the printer, switch off cooling fans, high bed temp, and don't print too fast. In combination with the huge shrinkage of ABS, this causes the splitting, or the coming loose from the build platform. ABS is good for injection moulding, but not so good for 3D-printing.

If PLA would not be suitable for your model, you might consider materials that have less shrinking and warping than ABS, but that print more like PLA. For example NGEN, PET, PETG? Try one spool, or even a sample, before buying a lot.

Completely agree with you. I should change my setting and try again.

I have try with PLA, much more easier, no problem at all. But just facing a problem that how to smoothing PLA printing. As I know, chloroform is the best choice, but hard to get it.

[Part start cracking while printing.]

Poor layer adhesion?  What is the print temp?

Perhaps try 20% or 25% infill?

What is the infill pattern?  You might want the infill pattern to be at a 45° angle to the layers.

Hi, thanks for advise. Yes, poor adhesion, or like warping after cooled down. While it happen during printing as well. Nozzle temperature is 260 degree, mostly I follow Cura standard setting.

Yes, you are right, I should try, to increase 20~25% infill.

How about layer and wall thickness? Any effect in this case?

[Part start cracking while printing.]

Recently I facing a problem on my printing parts. The part start to crack during printing, and getting more serious after cooling down.

Material : ABS

Profile : Normal

Layer Height : 0.2mm

Wall thickness : 1mm

Top/Btm thickness : 0.75mm

Infill density : 10%

Material enable retraction : YES

Printing speed : 55mm/s

Travel speed : 150mm/s

Enable print'g cooling : no

What is the root cause of this problem

Thanks!