We are pleased to have provided troubleshooting and upgrade assistance to a local mfg. of roll formed sheet metal products. We received a call that their main roll forming machine was down, and needed attention immediately.
We arrived at the plant and soon noticed that the PLC in the control cabinet was not communicating with the main PC computer. This is a fairly old system, the PC was operating with DOS! The PLC communicated with the PC over a Modbus/RTU connection. It appeared that the Modbus connection was no longer working, possibly pointing top a bad CPU, or faulty PLC back-plane.
The PLC is a DL305 from Automation Direct, which we have software and experience with. We worked with the plant personnel to order the needed replacement parts for next day delivery. Early the next morning we arrived at the plant to make preparation, we were able to get the program from the failed PLC after many attempts. Fortunately there was a paper copy of the program available, as the OEM did not have any record of the program. We spent time typing in the tag names for the ladder logic elements.
After the parts arrived on FedEx, which consisted of a new PLC rack, new PLC CPU, new programming acable, and ROM chip, we installed them, and after loading the program into the new CPU, the machine operated as it should.