The Case of the Faulty Carpet Printer

By John Dawson

I used to work for a carpet tile manufacturer as an Electronics Technician. They had a large Zimmer ink jet printer that printed designs onto the carpet tiles. Tiles were loaded onto the back of the printer, indexed and shifted into position and indexed up to the print head area. A large print head with jets that sprayed the various colors and pulsed to create the various designs moved across a gear rail and kept a feedback of position by an encoder with a wheel that rode along a metal rail.

We kept having problems with print quality. Other technicians kept replacing and adjusting the encoder and wheel assembly with no luck. Circuit boards used to pulse the jets were calibrated and/or replaced but still the problem persisted. I think some technicians had even suggested replacing the servo drive and motor used to drive the print head.

One night the problem was really bad. I started looking inside the electrical panel that housed the servo controller and inkjet boards. I happened to notice on one of the power transformers that supplied power to the panel had a discolored connection on one of the bolts where the incoming voltage connected. I powered down the equipment and power supply and cleaned the bad connection that had been arcing and had also corroded.

The problem disappeared. Operators and supervisors were very happy.

John Dawson is currently an Engineering Tech III at Auburn University Physics Dept. He has worked for over 20 years in industrial maintenance as well as an electrical designer in manufacturing plants.