Automated optical grading of large stones at Nordkalk Corporation

摘要

Nordkalk Corporation has been performing manual limestone grading, either by removing the dark stones from the line simply by hand or semi-manually by operating pneumatic driven discharge plates. The manual methods are physically straining and exhibit risks of injury in the handling of heavy stones on a moving conveyor belt. The semi-manual method is still labour intensive and can not provide 24/7 operation without excessive personnel resources. Haarla Engineering has developed an automated optical grading system is at the moment installing the third system at Nordkalk Corporation. The units are equipped with colour matrix cameras and full system automation thus removing all manual stages from the grading process. Working with big stones, the imaging is uniquely performed on the conveyor rather than from a free falling stone as typically done with smaller sized material. The automated line can run non-stop without personnel simultaneously controlling conveyor congestion, detecting the stones with 3D size recognition, performing the optical grading and controlling the production line. The easy to use touch screen user interface and the PLC-based platform combine easy use with a very long and rock solid service life.