In one example, an executable program on a computer-readable storage medium that instructs a processor to predict a characteristic of at least some parts in plural orders from a corresponding computer model of the part. The program also instructs the processor to assign, based on the predicted characteristics, models of at least some similar parts from different orders to different build trays usable to fabricate the parts. The program further instructs the processor to, for each build tray, sort the fabricated parts into the plural orders by matching a measured characteristic of a part to a predicted characteristic of unsorted parts from the build tray.