WHAT’S THE ISSUE?
For models with a flat top layer, it is a common problem that there is a hole in the top layer, and there may also be uneven.
∙ Poor Top Layer Supports
∙ Improper Cooling
Poor Top Layer Supports
One of the major reasons for pillowing is the insufficient support of the top layers, which causes the filament on the top layer collapses and form holes. Especially for flexible filaments such as TPU, stronger support is needed to form a strong top layer. Top layer supports can be strengthened by adjusting the slice setting.
INCREASE TOP LAYER THICKNESS
The most direct way to have good support on top is to increase the thickness of the top layers. Generally, the top thickness setting can be found in the advanced setting of shell thickness setting. The layer thickness needs to be set to a multiple of the layer height. Increase the top layer thickness to 5 times the layer height. If the top layer is still not strong enough, just continue to increase. However, the thicker the top layer, the longer the printing time.
Increase INFILL density
Infill density can also increase the support of the top layers. When the infill density is low, the voids inside the model are relatively large, so the top layer may collapse. In this case, you can increase the density to 20%-30%. However, the higher the infill density, the longer the printing time.
When the cooling is insufficient, the filament will solidify slowly, and not be easy to form a strong top layer.
Check the cooling fan
Enable a cooling fan when slicing, so that the filament can cool down quickly and become solid. Pay attention that whether the wind from the fan blows toward the print model. Increasing the speed of the fan can also help filament cools down.
DECREASE printing speed
During printing layers of small size, decreasing printing speed can increase the cooling time of the previous layer. This can prevent layer collapse due to the weight of the upper filament.
Increase the distance between nozzle and print bed
Increasing the distance between the nozzle and the print bed before the start of printing. It may reduce the heat transmission from the nozzle to the model, making the filament cool down easier.