CASE STUDY: Inspection - Vision Systems
A major softwood manufacturer approached Z-Tec about inspecting the grade stamps on the lumber produced in the mill. The driving force behind the idea was reducing manpower in the sorter area, resulting in no manual inspection of the grade stamps to ensure good quality of stamps and no miss-stamping. Miss-stamped lumber and/or poor quality stamp requires the manufacturer to rerun lumber, resulting in extra work and potential volume losses and thus reducing profit.
Z-Tec implemented a Cognex camera based vision system tied to the manufacturer's PLC, which compared the stamp to the data from the PLC to catch miss-stamping as soon as it occurred. The individual pixels in the stamp image were also compared to an ideal stamp to determine percentage of match.
The system detects poor stamp quality and/or miss-stamped lumber within a few pieces of lumber through the system and generates an alarm, which stops the line. This allows the operating personnel to correct the problem before the sorter is full of lumber which needs to be rerun, ultimately causing the facility reduced profits at best or a very costly recall possibly including a penalty, if the problem is not detected until after the lumber is shipped out.
A number of these systems are currently in operation, and in fact, Z-Tec offers the vision inspection option with all of their WinJet II systems to detect poor quality stamp due to dust or oil mist contaminating the print heads. With the WinJet II system, miss-stamping of lumber is not possible, thus the vision system is not required to detect wrong stamps.