Do I need to discard partially used QIAcube tip racks?
FAQ ID -1418

No. The QIAcube is equipped with an optical sensor, which determines the tip size and the number of tips loaded onto the worktable prior to starting a run.

The QIAcube can use partially used tip racks from previous runs, provided that the racks contain sufficient tips to process the number of samples loaded for the current run.