In situ multi-phase sensing for 3d printing

A three-dimensional (3D) printer, comprising:

• a build plate;
• a recoater configured to successively deposit layers of print material onto the build plate;
• an energy beam source configured to form a weld pool by heating selected regions of the print material in each layer to form a build piece;
• an image sensor configured to image an area including the weld pool to determine a landing location of matter ejected during the heating of the print material to form the weld pool;
• and
• a non-optical sensor configured to detect a defect in the build piece based on the determination of the landing location.

A method for 3D printing a build piece, comprising:

• depositing a layer of print material;
• heating a portion the print material in the layer with an energy beam to form a weld pool;
• sensing first information with a first sensor;
• determining, based on the first information, a landing location of matter ejected during the heating of the print material to form the weld pool;
• sensing second information based on the landing location;
• and
• detecting, based on the second information, a defect in the build piece based on the determination of the landing location.