Our Hardware Solution
We were told that our solution could not impact how the employees were doing their job, so it had to be an automated, hands free system. Fixed scanners at the work stations were not acceptable because it would slow down the employee, and fixed laser scanners at each station was far too costly. In addition, the conveyor travels at 350 feet per minute, which meant that we had about 300 milliseconds to process each tray.
We decided that what we needed was in intelligent camera, and decided to use the Cognex DVT 515 Vision Sensor. These were installed just downstream of each worker, and their job was to detect if a package was present or not. Two additional cameras were installed up stream of the first two stations to detect any packages that had failed to be diverted, and had made the trip all the way around the system.
The Accusort laser was used to confirm that a package was present in the tray, and the bar code was scannable. This also filtered out prevented "false positives" (i.e. bar code facing down, or an employee holding his hand in front of the camera) and the data output from the laser was processed to detect missing items from orders.
We built a custom controller using an Opto22 industrial computer. Each camera was wired back to a relay installed in the controller, and was sampled each time a tray passed a photo eye. We tied our system into the existing conveyor in order to detect a tray 1 pulse, and so we knew the location of each package on the conveyor.
We used Symbol Technology LS2208 laser scanners and Logic Control pole displays at each station to allow the employees to log in and log out of the system
The camera and laser scanners:
