mySelective 6748 selective soldering machine now has PCB warpage compensation. Is said to ensure points to be soldered are always the same height above the wave, even if board has slight warpage. A noncontact laser sensor measures the distance between an assembly in process and the wave prior to soldering. Measures the distance of several target positions on the bottom side of the assembly, while the board is held in the gripper (robot product handling device). Chooses a reference point (near the corner of the board) and a measurement point (near the middle of the board), and others if needed, so the sensor can take measurements and teach itself the board shape and degree of distortion. It then makes appropriate calculations (Z offset).
 
Vitronics Soltec, www.vitronics-soltec.com