Manufacturing engineer Jeremy Cook discusses a few machine failure problems that seemed complicated at the onset, but were quite simple to solve in the end, and the lessons he learned.
As you can see in my bio at the end of this article, I work as a manufacturing engineer. One of my favorite things that happens on a Friday late in the afternoon is to hear my phone ring and see the number of a technician come up: I just know he's going to inform me that a machine has just undergone some kind of catastrophic failure.
OK, maybe it's not my favorite thing to do, but if our jobs were fun all the time, we'd probably be working for free.
Although I've learned (hopefully) to appear outwardly patient and in control, at the back of my mind is the constant nagging fear that I will literally never be able to go home because I can't figure out what's going on. Or maybe I have now run into the one problem that finally can't be solved, and I'll get fired.
The good news is that I've always made it home (so far) and in some cases I've even made it home on time. What follows are a few problems that seemed complicated at the onset, but were quite simple to solve in the end, and the lessons I learned.
Case 1: Recently, I was called out to look at a machine because the vision system was working correctly, but the display was not. The technician who immediately serviced it said he checked the wires and cycled the VGA monitor off and on to no avail. Fortunately, I'd seen this before and, seeing the male side of a VGA cable lying on the floor, soon found its mate. I then stuffed it further into the machine where it would hopefully not get knocked out again.
Lesson: Make sure everything is plugged in!
Case 2: Another machine kept faulting out because a pneumatic cylinder was supposedly not in the correct position. The technicians claimed the sensors were working correctly, but after maintenance changed out a drive motor, things still didn't function correctly.
Our electrical engineer hooked up to the PLC with a computer, and after I manually manipulated the cylinder that we suspected the problem was coming from, all the sensors appeared to check out. Actually, there was one sensor that seemed to have some issue going on, but after adjusting the position, it appeared to work. I initially asked the tech to get more of these sensors but, after seeing it working correctly, decided this wasn't necessary.
After trying to troubleshoot this machine for another hour or so, I saw this sensor again not come on. We then changed it out and found the original sensor with frayed insulation at several points. The machine then performed as it should.
Lesson: Sometimes you should trust your gut, especially when it's easy to follow!
Case 3: Working with the same electrical engineer from the “Catastrophe!” before, we had a small touch panel that needed to be replaced. He loaded the program on, but unfortunately, we kept getting the message “Over Reject Limit.” The touch screen didn't seem to work correctly at all and wouldn't let us reset the counter. Then -- after quite a bit of troubleshooting -- I happened to swipe my finger across the screen in a way that made the screen change. Maybe the display wasn't set up correctly?
This particular touch screen had an option to calibrate the display. Naturally, we'd ignored it. Obviously, the problem was more complicated than that. Well, it wasn't. After running the calibration routine, the machine was able to reset correctly.
Lesson: If there's an option to calibrate equipment, it's probably there for a reason!
If you're ever in this situation (as undoubtedly most of our readers are from time to time), don't forget to check the simple fixes first. If that doesn't work, move on to the next set. I'll write about attacking those situations in my next blog.
— Jeremy Cook is a manufacturing engineer with 10 years' experience and has a BSME from Clemson University. You can find him on Twitter at