Case Studies

Cognex and Siemens S7 Inspection System

Posted in Food and Beverage, Manufacturing Automation and Intelligence, PLC Programming, Siemens PLC


An existing packaging line had no inspection for glue quality. Bad glue lines were occurring every several days, resulting in machine downtime since an unnoticed issue would usually cause a jam. DMC utilized a Cognex Checker Vision Sensor to interface with a Siemens PLC in order to provide an inspection system. This solution utilized previous reject methods and decreased line downtime.

Cognex Checker Vision Sensor


The machine control was already being done by a Siemens S7 315 PLC. Using digital IO, the PLC was interfaced with a Cognex Checker Vision Sensor. The Siemens PLC would request an inspection during a dwell time in the index. The sensor performed the inspection and reported back the result. The line stopped if there were five consecutive bad inspections, which indicated a glue tip issue.  Previously, these issues were only identified after 30-40 pieces had gone through the line.

The Cognex Vision Sensor was setup to inspect glue in four locations. If there was either too much glue or not enough glue, then it would not send a pass signal. The Cognex software allowed for very flexible setup and provided easy testing of the vision inspection parameters. The vision inspection took less than 30ms, which was faster than the system required.

The customer was able to use the new vision inspection to improve throughput of the packaging lines and increase knowledge of the cause of line issues.

Customer Benefits

  • Reduced downtime due to bad glue
  • Less wasted product when gluing did not start correctly
  • Less operator frustration due to reduced jams
  • Improved reliability of process


  • Siemens S7 PLC
  • Cognex Vision Checker
  • Siemens ProTool