Hi Bob Chen
That works well on a single conveyor belt, but if there are multiple belts, robots, boxes, parts, and a few tables, it won’t work unless the values are within a specific minimum and maximum range. Therefore, if the scene becomes large, these values must have a tolerance; otherwise, the scene will fail. It might work fine for the first three boxes, but the fourth one causes problems because the scan cycle breaks and the communication becomes unstable. This usually happens as more boxes and parts are added; it seems the motor, having to traverse so many elements, isn’t going to perform as well.
Look at the top right for the tolerance +/- 4, that is, the machine should start checking when there are 4 pixels missing before the piece arrives. If you want to do it exactly right, it won’t work because the communication will fail. Obviously, the lower the tolerance, the greater the precision; in this case, we are talking about 4 pixels.
In reality, it’s different, since there’s no simulator or PLCSIM, and you work directly from the PLC. Therefore, the communication speed is much better. I’ve tested it with a physical PLC, and that alone makes a significant improvement.
Regards