The general rule of printing slopes (overhangs) is that they shouldn’t exceed 45-degrees. The idea behind this is to ensure each successive layer has enough support to build up on. At 45 degrees, every layer is in about 50% contact with the layer below it and hence prints well.
Slope angles greater than 45-degrees, are generally chambered to print without supports. This however limits our design and creativity. Here are a few techniques that can be followed to print angles slightly greater than 45-degrees without using supports.
Cooling time plays a major role while printing overhangs. The faster you get the layers to cool, the better is the surface finish on the overhang. Orient your part such that the overhang area is facing towards the cooling fan. Use external fans if necessary.
To further improve cooling, the layer heights and the wall thickness can be lowered so there is lesser mass at every layer and hence faster cooling.
Modify your ‘Shell’ settings in ‘Ultimaker CURA’ or the ‘layer’ tab in ‘Simplify3D’ to print the inner layers before the outer. This will improve the surface quality of the overhang.
Note: The dimensional accuracy of the part in ‘X’ and ‘Y’ will be better if you print outer before inner layers. So, the tolerances of the part should be considered before making this change.
Increasing the number of perimeters makes the base layers sturdier making it easier for the subsequent layers to build up on them.
Lower your print speed to improve layer adhesion and cooling. With lesser speeds, the part is exposed to the cooling fan for longer times. You can also adjust the minimum layer time to control the speed in certain areas of the model.