Three-dimensional printing systems and methods of their use

An apparatus for three-dimensional (3D) printing a 3D object, the apparatus comprising:

• one or more controllers configured to:
• (i) couple to a power source;
• (ii) operationally coupled with the elevator, the layer forming device, the one or more galvanometer scanners, and the couple with a gas flow system of a 3D printer;
• and
• (iii) the gas flow system to provide flow of gas such that during the printing (A) the flow of the gas is across at least a portion of a processing cone region of an energy beam, the processing cone being in a processing chamber in which the 3D object is printed from a powder bed using the energy beam, and (B) the flow of the gas (I) is maintained at a debris concentration of from about one milligrams per cubic meter to about a thousand milligrams per cubic meter (a) in the processing cone region and (b) at least about 20 millimeters above a surface of the powder bed, (II) maintains a debris concentration for debris particles having a fundamental length scale of at least about 0.5 micrometers at a concentration of about 0.5 particles per cubic centimeter to about 1,000 particles per cubic centimeter, (III) a number of debris particles having the fundamental length scale of at least about 0.5 micrometers encountered by the energy beam is from about 10 to about 10,000,
• wherein the 3D printing results in the 3D object comprising elemental metal or metal alloy, the 3D object having a porosity of at most about one percent (1%) by volume.