I used to work at Nordson Corp., and it was there that I ran into two Sherlock-worthy problems:
First, the company had hot-melt glue applicators ranging from units with small tanks (that glue was added to as small pellets or chips), up to a 55-gallon drum in heated-platen units. One of the 55-gallon drum units had an overheating problem.
When the line started, the LED indicators flashed, showing the heating cycle. The temperature display showed the temperature was rising. As the temperature neared the set point, the PID (proportional integral derivative) compensation was supposed to reduce the heat, and the LED flash rate slowed to mimic the change. But the temperature kept increasing until the over-heat tripped.
When this happened, the unit had to be allowed to cool before any testing could be done. The heating was controlled by a triac (triode for alternating current). When the unit cooled, I monitored the triac control voltage and output voltage. Even when the triac control was not on, it was heating, so the triac was shorted.
When I explained to the manager that I would need to replace the triac, he said that there wasn’t a replacement in stock. I checked stock myself, and found a replacement that would work. The triac for the 55-gallon unit was the same triac as was used on the tank-style unit. The two had different Nordson part numbers, but they were the same triac. After I replaced the triac, the over-heat problem was fixed.
Next, I experienced another line snafu. Our company had sealant dispensing units at the General Motors Oshawa Car Plant. There were two units on one line, and one wasn’t working properly. The plant was still in start-up, so the problem was not urgent. Another technician had been working on the unit, but had not been able to fix the problem. I was asked to look into the situation. I asked the technician for the details of all the testing he had done.
He narrowed the problem to a ribbon cable, but when he replaced the cable, it didn’t fix the problem. When I got to the plant, I asked if it would be a problem to shut down the other, working unit. We shut the working unit down, pulled the ribbon cable, and installed it on the non-working unit. That unit powered-up and worked. We then installed the suspect cable in the first unit. That proved the cable was the problem. The replacement cable also happened to be faulty. When available, swap-tronics can be a big help.
This entry was submitted by Glenn Aitchison and edited by Rob Spiegel.
Glenn Aitchison’s first field service job was in 1987. Since then he has worked in robotics, automotive, as well as industrial automation and machinery. He received his Certificates of Qualification as an Industrial Electrician and as an Industrial Mechanic (Millwright).
Tell us your experience in solving a knotty engineering problem. Send stories to Rob Spiegel for Sherlock Ohms.
In the early 1980s, a fellow engineer (of Chinese descent) told me quite emphatically that he AVOIDED doing ANY business with anything connected to the Chinese (as a nation) because of their unethical behavior. Since this was at a time in history which was less than 10 years removed from Pres. Nixon's historic trip to mainland China, I immediately dismissed his comments as being very biased & bigoted. At that time the world was not so deeply engaged with Chinese manufacturing & trade.
Now, however, as I reflect on those comments from decades ago, and become more aware of the devious business practices that are undertaken AND sanctioned by the "higher-ups", it is becoming more apparent that his comments bore a great deal of validity, SORRY to say!
I'm SURE that with every other endeavor in human relations, one can find the "bad apple" which seems to rise to the fore, make the news, etc. whereas the rest of the barrel of apples goes completely unnoticed and/or unrecognized!
p.s. During his diatribe against the Chinese, he mentioned one startling fact...... he'd MUCH rather engage in business deals with a Japanese company or entity since they ARE so ethical.
In the late 80's during a business trip to Russia I was given a tour of a fabrication facility. Standing on the mezzanine with my interpreter and 2 managers we overlooked a floor with probably 70 lathes and at least 50 milling machines, all being operated. Sitting right in the middle of the floor was a very modern multi-axis CNC machine surrounded by yellow lines on the floor and sitting idle. Upon seeing the CNC machine I asked why it was idle? The manager smiled and said that machine could replace 5 skilled machinists and produce 3-4x the volume, but "you understand in Russia, we can have no unemployment". The only time the CNC machine was operated was when dignitaries from the central Government came to visit. From stories I gather China has smiliar problems.
Glenn Atchison wrote "When this happened, the unit had to be allowed to cool before any testing could be done. The heating was controlled by a triac (triode for alternating current). When the unit cooled, I monitored the triac control voltage and output voltage. Even when the triac control was not on, it was heating, so the triac was shorted."
"Latchup" is the most common failure mode of triacs. They remain in the "off" (non-conducting) state when power is applied until the trigger voltage is first applied to the gate. Then they turn "on" (conducting) as they should. The problem occurs when the trigger voltage is removed from the gate. The triac should turn off at the first AC voltage zero-crossing but it does not. The device "latches up" and remains conducting until voltage is completely removed from device terminals. In other words, the triac won't reset until the product is completely powered off.
I had the same failure and related symptoms in my 1984 washing machine in about 2007. A new controller board would have cost $350, but they were no longer available. I isolated the problem to the triac, as Glenn did. Also similar to Glenn's experience, I could not get an identically-labelled replacement--no longer made. But triacs are not critical components. Any one with comparable or greater ratings and a similar package will do. Fortunately replacements were available for 37 cents.
Rob, I think that philosophy falls under what in ethics is called utilitarianism. In their minds it brings about a desired result (employment for a large number of people) therefore it is good - the means are not as important as the end. It's especially hard to fight in this case because it is part of their worldview...
Yes, I remember that comment during the debate. And that's how a lot of it works. I remember a story about a plant in a small town in China that was producing counterfeit components. Officials were apparently well aware of what the plant was doing. When an Chinese official was asked why the government didn't shut down the plant, he replied, "This plant employees 2,000 people. It's the biggest employer in town by far."
That reminds me of what Mitt Romney said during one of the debates, Rob. The topic was about trade with China and Romney was talking about some type of valve that came back to the manufacturer as defective, so the company replaced it. But the company noticed something was wrong when they got several additional defective valves returned - all sporting the same serial number!
That's a good story, Nancy. With counterfeit parts, it can be really bad. The parts often come back to the distributor or supplier in its own packaging. They look and act right -- the first layer or the first part of the roll. After that, it's garbage. In the independent distributor market, their association offers classes and certification on how to identify counterfeit parts.
It is tempting to assume that because something is "new" that it is good...we forget that manufacturing processes can shift and sometimes entire lots of "new" stuff with a defect escape QC before it is detected and wind up for sale. Kind of the same idea - I remember one time I bought several red LEDS for a project I was building, from the same place I usually bought my parts from. My project was a wind rose being controlled by an 8751 and different color LEDs would light in response to changes in wind strength and direction. After I soldered in the LEDS into my homemade PC board, I was amazed that my "red" LEDS were both "orange" red and "red" red. I just couldn't understand how I could buy something new and have that much variance in the same product. I went back to the electronics store I had bought the LEDs at and because I wanted my LEDs to match in color, I powered them up before I bought them (with the store manager's permission) so that I could get matching colors. That went a long way in teaching me not to assume that what I purchased would meet my expectations, regardless of how well prior purchases had worked in the past.
naperlou; The cable was new from stock. It had never been installed into a machine before. Fortunately I had a known-good cable in the working unit to use for troubleshooting. But 'swap-tronics' only works when you have multiple identical units to swap parts between.
From Dell / Intel® New Paradigms in Design Work Scott Hamilton, vertical market strategist for Dell Precision workstations, 5/2/2013 5
Early in my career, I worked as a draftsman and remember the days of drawing on vellum with numbered pencils and Mylar with plastic lead. This was a fun experience in the sense that I ...
I've been using workstations for more than 10 years and love finding ways to get more performance from my system. With demanding professional applications that require more power each ...
A lasting memory from my first job as an engineer in an auto assembly plant is standing on hard concrete at six in the morning, vending-machine coffee clutched in hand, listening to ...
For industrial control applications, or even a simple assembly line, that machine can go almost 24/7 without a break. But what happens when the task is a little more complex? That’s where the “smart” machine would come in. The smart machine is one that has some simple (or complex in some cases) processing capability to be able to adapt to changing conditions. Such machines are suited for a host of applications, including automotive, aerospace, defense, medical, computers and electronics, telecommunications, consumer goods, and so on. This radio show will show what’s possible with smart machines, and what tradeoffs need to be made to implement such a solution.
To save this item to your list of favorite Design News content so you can find it later in your Profile page, click the "Save It" button next to the item.
If you found this interesting or useful, please use the links to the services below to share it with other readers. You will need a free account with each service to share an item via that service.
Tweet This
7 
