Lifting columns extend the robot reach by adding a virtual 7th axis to the robot. The current position of the lifting column is a parameter in all calculations in the Pally path planning.
Lifting columns can have 2 or more valid positions. 2-position lifting columns are typically built with end-switches (up/down positions) while other models such as the Ewellix eLiftKit have continuous positioning with position feedback. When continuous positioning is available, Pally will choose intermediate positions that correspond to multiples of layer heights. Otherwise, the lifting column will be elevated when the pallet height reaches the stroke of the column, see figure 8.
Each layer is palletized with the best lifting column position by default, but custom configurations are also possible by defining zones manually.