The problem
The spiral blast freezer was still doing its job, but it ran on an Allen Bradley SLC 5/03 PLC and a Red Lion HMI, both obsolete. The company that built the freezer had gone out of business, so there was no OEM support, nobody to ask for the program, and replacement parts were getting harder to find.
The client was concerned that one failure could take the freezer out of production with no clear way back.
What we did
We took a backup of the original PLC and reverse engineered the program, working through the logic to document how the freezer actually ran: its operating modes, the drives, and the belt control that carries product through the spiral.
The control system was then rebuilt on a Mitsubishi iQ-R R04EN PLC with a GOT2000 GT2510 touchscreen, keeping the original functionality the operators relied on.
To keep the changeover short, we made up conversion cables in advance so the new PLC could connect to the existing panel wiring, rather than rewiring every I/O point on the day.
The new HMI gives operators screens for freezer mode, drive enable, retention times, parameters and alarms, with a separate engineer login for settings.
The result
The freezer now runs on current, supported hardware with spares available. The client has a documented, commented program that they own, in place of an undocumented controller from a company that no longer exists.
