The “Shotgun” Approach to Troubleshooting

It is estimated that 67% of parts returned to warehouses are not actually defective. We see this all the time at PDF Supply. We go through an extensive electrical testing process with parts when they come back to us, and many times, we find that there is nothing wrong with these components. Why do so many perfectly good parts take the blame for problems that occur in machinery and control systems? The answer is that technicians often do not understand the real nature of the problems they encounter.

Being on call for technical support is a stressful situation. When you have a plant supervisor standing over you and wanting to know how soon the equipment will be back up and running, it’s easy to get unnerved. Line employees want to get their shifts done and go home. Everyone is under pressure. With people watching you and looking at their watches, it’s better to look busy. The worst thing you can do is stand their scratching your head and looking at the machine. Under the spotlight, it’s understandable to feel the impulse to start removing chassis screws, pulling cards, and doing anything to move things forward.

Many technicians are taught to approach triage situations using the “shotgun” method—replace all major components that usually are the source of machine problems. This is the most expensive way to repair a machine, and it doesn’t always work. You can replace the PLC, the servo drive, all of the I/O cards, the motor—anything you have a replacement part for—and still fail to address the root cause of the problem. What if there is noise on a signal bus? What if there’s a mechanical issue in a machine that’s causing an overcurrent condition? What if there is a loose cable? The tendency to replace components unnecessarily is driven by the urgent need to make something happen fast, and that can cause you to make a bad situation worse. What happens if, for instance, you replace a controller card only to find that you’ve now destroyed a second controller card—which was your one and only spare?

The “shotgun” approach to troubleshooting is not entirely a bad thing. You just have to recognize that there are pros and cons. Sometimes, pulling all of the major components is ideal for getting a system back up and running, provided you’ve taken some basic troubleshooting steps first and decided to accept the risk of this method. Also, if you have a process for testing components in house, you can pull all of the parts and test them later to find out if any are bad. But the bottom line is this: it is crucial to have a standard process for troubleshooting machine breakdowns, especially during high-tension scenarios like critical production runs. Downtime is expensive, but losing your cool can create even more downtime.

Ideally, you should strongly consider deciding ahead of time when it will make sense to use the shotgun approach. What conditions make this approach logical? What other steps will you try first? Having a proactive plan can make all the difference.

This entry was posted on October 23rd, 2013 and is filed under General, Technology. Both comments and pings are currently closed.