To smaller sizes, you need to ensure that there is enough foundation to support the side wall of 20mm square. There are usually several reasons for weak foundation. Refer to the following for details:
Note: adding more contours to the print will significantly enhance the foundation, because the inside of the print is usually partially hollow, and the thickness of the outer wall will have a great impact. There is a wall thickness setting in the basic setting. The wall thickness setting is generally in the multiple of the nozzle. For example, if your nozzle is 0.4mm, the wall thickness is generally set between 0.8mm-1.6mm. If you set 0.8mm at the beginning, but there are holes in the outer wall of the printed model, you can appropriately increase one or two layers of wall thickness to improve it, The appropriate wall thickness is generally 1.2mm, which will not take too long and the printed model will not have holes.
Insufficient number of top solid layers
Solution: increase the number of top-level solid filling layers
Note: another common reason for the weak foundation is that the number of solid filling layers on the top layer of your print is insufficient, and the thin upper wall cannot fully support the structure printed on it. Modify this setting to open the basic filling bottom layer / top layer thickness. If the default thickness is 0.8mm, but the printed holes are still not fully filled, Then you can set the thickness of the bottom layer / top layer to 1.2mm, which can make the top layer and bottom layer more closed.
Filling rate is too low
Solution: set to increase the filling rate
Note: the last setting you need to check is the filling rate, which is controlled by a slider under the "slice settings" or the "filling" tab. The top solid layer is built on the top filling, so it is important to have enough filling to support these layers. For example, the fill rate you set before is 20%. Try increasing this value to 40% to see if the print quality has improved.