Automatic detection of mechanical defects in piece parts, such as floor covering planks, enables removal of the defective parts off an inspection path. A bypass conveyor system enables defective parts to be transported beyond or around a manual inspection, enabling personnel performing the subsequent inspection to focus on appearance defects. Once the remaining parts have been inspected by a manual process, the parts transported by the bypass conveyor system are returned to the production line. Defective parts may be distinguished by a marking capability that provides the ability to mark according to a variety of classes of defects.