Glue Troubles Run Hot & Cold

For a time, I worked for Nordson Corp. The Applications Division was mostly hot melt glue applicators. One customer had just installed a new unit, and it would not power up. The first thing I checked was the incoming voltage. It was 275 volts on a nominal 220V service. I told the customer that the main board may have been destroyed by the high voltage, but that I couldn't replace the board until the service voltage had been dropped to 220 plus or minus 10 percent.

After the service voltage was corrected, I returned with a replacement board. I confirmed the service voltage, and then I inspected the main board. The main board had a jumper for single-phase or three-phase power. The jumper had been set incorrectly. I corrected the jumper and installed the board to test it, and it worked. I explained to the customer that the jumper setting may have been what saved him $1,700 for a main board.

Another problem that I worked on at Nordson was a cold glue system. The application was presentation folders running at about 100 per minute. The timer had adjustments to compensate for the opening time of the glue gun. Part of the adjustment process was locating the sensors far enough ahead of the gun to allow for the response time. If the sensor and gun were too close together, a red LED would flash. This application became a problem. The senior service technician had not been able to tune the timer. Another technician had also tried and failed. The service manager had also tried.

So when my turn came, I knew it would be interesting. I had used a similar timer in some laboratory testing, so as I was working through the instruction manual setup sequence, I noticed this unit had three dip switches to set the gun open compensation, while the laboratory unit had four switches. After trying several adjustments and tuning the advance, I ran out of adjustments. I suggested to the service manager that the problem looked to be that the gun open response time was longer than the available adjustment of the three-switch unit, but the four-switch unit might have enough range. I returned to the customer, swapped the four-switch for the three-switch, and redid the tuning sequence. After several attempts to locate the sensors and tune the compensation, it finally worked.

This entry was submitted by Glenn Aitchison and edited by Rob Spiegel.

Glenn Aitchison got his first field service job in 1987. Since then, he has worked in robotics, automotive and industrial automation, and machinery. He received his Certificates of Qualification as an Industrial Electrician and an Industrial Mechanic (Millwright).

Tell us your experience in solving a knotty engineering problem. Send stories to Rob Spiegel for Sherlock Ohms.

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