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.
That's interesting that the two mistakes (voltage and jumper) saved the day. If there hadn;t been the second mistake, the first mistake would have cost $1,700. Thanks goodness for the second mistake.
The glue problem looks even more interesting to me. Why didn't the other people who troubleshot (is that a word?) this problem realize the conclusion that the author came to?
That is a great question, Ann. Yet, as we've seen with so many of these Sherlock Ohms postings, something as simple as the amount of voltage going to the unit gets overlooked.
How about TROUBLESHOOTED?? That sounds even more grotesque! Or, maybe the past participle TRUBLE SHOOTEN?
That's what's so perfect about the GERMAN language. They have a specific word to indicate exactly what they want to say, WITHOUT 99 exceptions of revery rule of language (as in English!)
Ann R. Thryft; Other than knowing the other techs were unsuccessful, I didn't know what testing they had done. I did have the advantage of more experience with that timer from running laboratory tests.
I also have the bad habit of reading manuals and instructions. Some technicians seem to believe 'real men don't read manuals'. The solution may be hidden in an unrelated chapter, or only inferred to, but many times the answer is in the manual. On the other hand, unless the manual is formatted to be printed, it may be useless. An on-line manual needs to be formatted so that it can be flipped through page-by-page. The example that I use of a poor manual was trying to find how to delete a chart in Excel. You can't 'delete' a chart. You can't 'erase' a chart. But if you already knew how to 'remove' a chart, you wouldn't need the manual.
Glenn, sounds like your predecessors didn't work as carefully or methodically as you did. I'm also a fan of reading instructions before proceeding with building, installing, or troubleshooting something, or using a new machine. First, I read through the procedures at least once to make sure I have all the tools and supplies I need, and to determine where I'll be doing a repair or assembly task: a table, the floor, outside on the deck, etc.
I wish I had your discipline, Ann. I usually just dig in and refer to the instructions when I run into trouble. I think the value of each approach depends on the quality of the instructions. I recently had a clogged vacuum. When I wasn't able to locate the area of clogging, I turned to the instructions. They were of no help. So I continued a trial-and-error approach until I found and fixed the problem.
Manuals should have a good index with cross references. What someone thinks of as a temperature sensor, someone else might think of as a temperature switch or temperature detector. So listing all three in an index helps people get to the information no matter what they call something. Indexing requires patience and thoroughness.
I find the lack of cross references particulary troublesome in software books and documents. In a C-language reference book I use often, I find two references to hexadecimal numbers and hex numbering in the index. But no reference to how to format data to display it in as hex values. In a perfect world, the index would include:
hexadecimal, printing of
hexadecimal, display of
Under the heading of printf my book's index points to pages about printing floating-point numbers and strings, but nothing about other formats such as scientific notation or octal. An index makes or breaks documentation.
One of the BEST "books" containing an index is the McMASTER CARR SUPPLY catalog. There is so much redundancy that it is almost sickening, but as was posted, one person's widget might be someone else's doohickey. Nevertheless, they both exist in that index. Sure makes life a lot easier when poring through a catalog of 5,000 + pages.
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