Hello all. Some background: Here at the shop, we have an American lathe that we are starting to experience some issues with. This machine was installed sometime in the 1940's, and has had a new motor installed as well as drive system within the last 20 years (DC).
We have always been able to thread on this machine as intended without any issues. However, when trying to thread the end of a Mandrel shaft in low gear, when the system comes under load, the RPM decreases. With each cut (increased load), The RPM slows down more and more, until it reaches the 10% RPM deviation range, and then the system faults out, ultimately wiping out the threads and ruining the part. When we attempt to thread in high gear, there are no issues and it makes the cut fine. In low gear, our machinist who runs the machine typically cuts around 70-75 RPM, and has never had an issue until now. We tried to change the fault % to 20 but it still slows down more and more until it faults. We took out the clutch brushes and they definitely needed replaced from wear, however this proved to not be the issue after the machine faulted again with the replacements. I haven't been able to find anything related online, and I am not sure what to look at next. Any and all advice would be greatly appreciated!
Disclaimer:
I am an entry level electrical engineer, with no knowledge on these old systems and no mentor here at our shop, so bear with me if I don't understand something or misspeak on terminology.
We have always been able to thread on this machine as intended without any issues. However, when trying to thread the end of a Mandrel shaft in low gear, when the system comes under load, the RPM decreases. With each cut (increased load), The RPM slows down more and more, until it reaches the 10% RPM deviation range, and then the system faults out, ultimately wiping out the threads and ruining the part. When we attempt to thread in high gear, there are no issues and it makes the cut fine. In low gear, our machinist who runs the machine typically cuts around 70-75 RPM, and has never had an issue until now. We tried to change the fault % to 20 but it still slows down more and more until it faults. We took out the clutch brushes and they definitely needed replaced from wear, however this proved to not be the issue after the machine faulted again with the replacements. I haven't been able to find anything related online, and I am not sure what to look at next. Any and all advice would be greatly appreciated!
Disclaimer:
I am an entry level electrical engineer, with no knowledge on these old systems and no mentor here at our shop, so bear with me if I don't understand something or misspeak on terminology.
