This is a dual 24" monitor stand I have designed to be 3D printable.
****Use this at your own risk***. If you don't understand basic structural design concepts and are a beginner at 3D printing I do not suggest you attempt this project. I am not responsible for you damaging your screens!
As always, a reminder that people take time to design and share models with you free of charge, therefore please upload photos of makes (you don't want me to start selling them instead do you?) :)
I'm finding I can get really good strength of parts (it's all about how you design and orientate for printing). Print high infill. Solid infill for Monitor mount sections. At least 33% infill everywhere else. Leave the orientation of parts as is. They are this way so that the stress is carried across multiple layers, not across the grain (i.e. layers don't like direct shear forces applied to them). the screenshot is with my 24" screen and 19" older screen. Seems to work.
This is a work in progress as I haven't printed it yet, but I know it will work. Provide a steel pipe to mount to, (designed for some 33.6mm thick walled stainless pipe I have lying around - odd size I know it's imperial). The bolt sizes are 8mm, use locknuts. Glue and screw the monitor mount together (unfortunately this is the only way to make sure the part is good in torsion, shear and bending).