AutomationTechBrian
Lifetime Supporting Member
I'm a little frustrated with an automated saw on a plastic extrusion machine. It's always been the "trouble child", and it must be operational to produce good, clean plastic sheets. Thus, when it goes down, production comes to an immediate halt. ...and everyone looks to me to fix it.
Just in the past couple of months, we had to replace two transformers (which transformed the 480vac to 120vac and 240ac) at separate times. Then, it had a analog servo card (Control Logix, M02AE card) that went bad, so we replaced it. Then, the saw VFD burned out, and I replaced that. Now... I suspect the servo card has failed again. It happened on Friday, so I'm still waiting to confirm with the distributor's tech help Monday morning.
I'm beginning to suspect voltage/current issues, because when something fails, there is usually a corresponding "event" that precedes it. This time, it was something simple. Here's the email I sent the vendor:
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The customer was operating the saw normally when he realized that there was an anomaly in the plastic that would bind the saw up. So in the middle of a cycle, he hit the E-Stop... which we've done several times before without issue. The saw returned to home successfully, but....
When he cleared the E-Stop and reset the fault, the servo SLAMMED the top of the saw against the frame. He called me and I went over there immediately.
Troubleshooting... I found the analog output on the card was stuck with an output of -12.xx VDC. Prior to finding the voltage on the analog outputs, every time I reset the program, the servo slammed the top against the frame and the servo faulted out with an over-current. During the course of the night, I re-started the PLC several times and the output never cleared.
I should point out that the -12 VDC is a level that is unusually high for a "return" motion. Usually, the saw would gently move back to home after a cycle. The -12 VDC causes a fast, violent motion. I can't explain why it's so high, other than the card is faulty.
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My question to this forum...
If you were in charge of this saw, and it seemed like electrical components were failing with abnormal regularity, what would you do to either investigate the problem or safeguard the machine?
I should add that the main circuits are fused, and there are breakers on each device within the panel.
Thoughts are appreciated! Thanks!
Brian
Just in the past couple of months, we had to replace two transformers (which transformed the 480vac to 120vac and 240ac) at separate times. Then, it had a analog servo card (Control Logix, M02AE card) that went bad, so we replaced it. Then, the saw VFD burned out, and I replaced that. Now... I suspect the servo card has failed again. It happened on Friday, so I'm still waiting to confirm with the distributor's tech help Monday morning.
I'm beginning to suspect voltage/current issues, because when something fails, there is usually a corresponding "event" that precedes it. This time, it was something simple. Here's the email I sent the vendor:
**********************
The customer was operating the saw normally when he realized that there was an anomaly in the plastic that would bind the saw up. So in the middle of a cycle, he hit the E-Stop... which we've done several times before without issue. The saw returned to home successfully, but....
When he cleared the E-Stop and reset the fault, the servo SLAMMED the top of the saw against the frame. He called me and I went over there immediately.
Troubleshooting... I found the analog output on the card was stuck with an output of -12.xx VDC. Prior to finding the voltage on the analog outputs, every time I reset the program, the servo slammed the top against the frame and the servo faulted out with an over-current. During the course of the night, I re-started the PLC several times and the output never cleared.
I should point out that the -12 VDC is a level that is unusually high for a "return" motion. Usually, the saw would gently move back to home after a cycle. The -12 VDC causes a fast, violent motion. I can't explain why it's so high, other than the card is faulty.
****************************
My question to this forum...
If you were in charge of this saw, and it seemed like electrical components were failing with abnormal regularity, what would you do to either investigate the problem or safeguard the machine?
I should add that the main circuits are fused, and there are breakers on each device within the panel.
Thoughts are appreciated! Thanks!
Brian
