This is a parametric corner shelf to be printed without support as one piece.
Feel free to download source SCAD file or modify your parameters in Customizer.
Any corrections or complains are welcome in Comments section.
The attached STL file parameters were (all units in mm):
radius=150; // radius of the shelf
thickness=5; // thickness of the shelf
previs=thickness+5; // this is the front side of the shelf (let's make it a bit bigger) - default value should be OK
support_l=40; // length of support for screw
screw_d=4.2; // screw diameter
support_thickness=5; // thickness of the "leg" (default value is usually OK)
support_width=screw_d+10; // width of the "leg" (defined as screw hole + 10mm)
corner_hole=10; // radius of corner hole (for cables etc.)