How do I 3D Print Sharp Angles?

Hi, I am trying to 3D print a model of a bipropellant rocket engine that I am going to be machining soon. I printed it all in parts, but when I glue it all together some problems arise. Thus, I would like to print it all in one print. Any help would be appreciated. Link to my model.

Thanks!

UPDATE: Illusi's solution solved my problem! Thanks!