PLC vs Relay Logic: When Is It Time to Retrofit Your Old Machines?

Hundreds of machines in Bangladeshi factories still run on hard-wired relay panels. They work — until they don’t. Here’s how we advise clients to decide when a PLC retrofit makes sense:

Retrofit now if: spare relays are hard to find, fault-finding takes hours, you need recipe or batch changes, or the machine causes more than two hours of downtime per month.

Wait if: the machine is simple, spares are plentiful and it rarely fails.

A typical single-machine retrofit with a Siemens S7-1200 or Mitsubishi FX5U, a 7-inch HMI and clean rewiring costs far less than one week of lost production — and pays back through faster changeovers and easier troubleshooting.