HongKai

Over the years in after-sales service, I’ve encountered all sorts of customers. But one incident stands out more than any other.

I got a call from a customer in Southeast Asia – their sheathing line had been down for nearly two days.

The fault was very typical: the extruder could still heat up, the screw could still rotate, but the capstan and take-up were out of sync – the machine would alarm as soon as it started. The customer’s electrician had spent a full day troubleshooting – checked the wiring, replaced relays, rebooted the PLC – but nothing worked. Eventually, they concluded the PLC was faulty and were preparing to order a replacement.

I said: “Hold on – don’t rush to replace anything. Let me take a look via video call.”

“Open the control cabinet door – let me see the wiring.”

After the video connected, I had him open the control cabinet and go through the wiring. The wire labels were clear, nothing was loose, and there were no burn marks.

“Do you have a multimeter?”

He said yes. I had him set it to voltage and check the 24V supply to the PLC output module – it was normal. Then I had him check the analog input terminals on the inverter – no voltage.

“The signal isn’t getting through,” I said. “Trace this wire back and see if there’s a break somewhere.”

He searched for a while and found a section of cable between the control cabinet and the capstan motor – chewed by rats. The insulation was broken, and two wires had shorted together. After reconnecting them properly, the machine returned to normal. Total time: less than an hour.

The customer laughed on the other end of the video: “So a rat cost me two days of production!”

Later, he told me he had contacted other manufacturers, and their first reaction was “replace the PLC module” – quoting over 20,000 RMB and a week’s wait for shipping. He didn’t spend a single cent on new parts, and the problem was solved.