Modular Bookshelf / Shelving Unit

Each unit measures 320 x 320 x 200mm, which can accommodate most book sizes, and requires an H2 series printer. Every two adjacent units are secured using at least two M4x16 screws and two M4 nuts (a maximum of four M4 screws can be used).The wall thickness of each unit is 10mm. 10% 3D Honeycomb infill is recommended. The weight is approximately 770g. So far, I have tried combining up to 16 units together (4*4).