Abstract: To improve the operation of 3D printing systems, techniques are disclosed for a rotary 3D printer comprising: a main rotating support table rotating about a first axis and one or more secondary support tables rotating around a non-coaxial secondary axis; a powder supply assembly for distributing powder onto the tables; and an energy system for directing an energy beam at the powder to form a part. The main support table and secondary support tables can rotate in the same or opposite directions. Disclosed techniques include: grooved support table surfaces for improving stability of applied powder; reciprocating bellows for controlling a differential load on actuators that move the support tables; high temperature bearings or bushings for supporting rotary motion at high temperatures; and a mechanism for counterbalancing a weight of the part being built.