Set the overhang parameter in Blender 3D printing tool box I'm  working on a cube in Blender. I just deleted one of the faces (the top face) of the cube and added solidify to avoid non manifold edges.  

In this case, when I check the design it shows that the bottom face is an overhang face (shown with yellow color). However, if I change the overhang parameter in 3D printing tool box from 45 to 90° and then check the model, it doesn't show any overhang faces and it seems that everything is okay. I don't think increasing the overhang parameter could be a good idea. However, this is my first time that I'm trying to design a model for 3D printing. Can this model with the overhang parameter equal to 90° be printed using a 3D printer? How can I fix the overhang problem in this simple model. 



Today I tested another simple model. I used a fill circle and added solidify to the model. Although the model is really simple, check the model shows the same as the previous design - the bottom face is an overhang face. It seems that adding solidify to a shape leads to this problem. I don't know how can I fix this problem. Changing the overhang parameter fixes the overhang problem but it seems that this not a good idea for printing models.

Unfortunately, I can not test the print myself as I do not have a printer myself and I need to outsource the print job.
You are looking at overhangs in the design tool.  What matters are overhangs when printing.

When designing the object, the coordinate system is convenient for working with the object.  Before slicing, the object can be rotated and repositioned for better printing.  Only after is it positioned for printing can the actual overhangs and bridges determined.

Unless you wish to limit yourself to the design tools coordinate system, I wouldn't have the design tool generate support material, and I would ignore its comments about overhang angles.  First, bring the object into your slicer, position it on the print bed, and only then evaluate the need for support material.

To be honest, I often have a printing strategy in mind while I am designing an object, but when the object hits the printer I sometimes completely change my plan.