Wednesday, September 25, 2013

Does your vision system need a PLC?

Machine vision systems need to communicate with sensors and motion control devices. Usually a PLC manages moving the object to be inspected in front of the camera, listening to sensors and talking to the motion controller as necessary.

Sometimes though, there is no PLC. I’ve seen number of situations where machine vision had to be installed on an antiquated line that still used relays. When that happens there’s no option but to ask the PC to track parts and talk to drives.

But there are advantages to doing everything on a PC. Put simply, you can use whatever software you want, rather than being tied to ladder logic and whatever protocols a vendor provides.

That’s the argument adopted in “Deterministic Motion Required” published on the Control Design website, September 11th, 2013. Now this lengthy article describes a situation where aging machine tools were being upgraded, but I think the points are just as valid for a vision application. Don’t just assume a PLC is the best way to do it.

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