If the layers do not bond / melt together and individual layers warp within your part, this is called layer separation.
Adjust the nozzle temperature
The adhesion between layers can be increased with higher printing temperature. Although if you recognize that the extruder sometimes has a hard time to push the Filament trough the hotend, it´s maybe because your nozzle is too cold. Try to rise the temperature by 5-10 degrees so that the plastic flows easier.
Adjust layer height
If you have problems with layer separation, one of the first settings you must check is the layer height.The layer height depends on the nozzle size you are using. Most printers have a nozzle diameter of 0,3 to 0,5 millimetre. As general formula for the maximum layer height, you can take 75% of the diameter of your nozzle – e.g.: for a 0,4mm nozzle, set the layer height to 0,3mm.
Part cooling fan
Sometimes disabling or slow down the part cooling fan could be a solution for separated layers. But it depends on the material you are using. For PC, SEMIFLEX and ABS we recommend disabling the part cooling fan, for PLA, PET-G and other materials please try out other solutions.
Dry the filament (PA12)
PA12 / Nylon is a hydrophile material, that is why you must dry it before printing. ABS is not as hydrophile as PA12, so it should be enough to store it in an airtight container or bag after printing. As a rule of thumb, 100g of PA12 should be dried in an air circulated oved at 70-90°C for about 3-4hours.