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Hardinge Conquest T51 X-axis hardware overtravel - my fault, but how to recover?

Jim Wilson

Mar 25, 2007
Tucson, AZ, USA
Please help me correctly recover from a severe X-axis hardware overtravel.

Short Story:

I powered up my lathe with the X- and A-axis motor leads disconnected at the servo amp. Wham! The carriage fell from its top position all the way down against the hard stop at the bottom.

Unsurprisingly, I now have a 501 X-axis hardware overtravel alarm. What is the right way to recover from this?

The lathe is a Hardinge Conquest T51 with a Fanuc 18T control.

Long Story:

This machine has been running fine, very light duty, for quite a few years. The other day, we got a surprise on startup: 400 alarm and 414's on both X and A (turret) axes.

The servo amp motor leads all read > 25 Mohm against each other and GND for both X and A (turret) axes. The fact that both X and A alarms appeared at the same time suggested to me that maybe the servo amp is to blame.

Powering up (motor leads re-attached), I noticed the servo amp LED Status display only briefly flashed a 2 before going blank. The servo amp fuse checked good. I guessed maybe the 5V leg of the power supply is failing, so I opened up the servo amp. It was quite dirty and sticky. I wondered if maybe a cap or power resistor had released its magic smoke, but there was no clear localization of overheating or soot. I removed the power supply and inspected it carefully but did not find any obvious signs of failure. I thoroughly cleaned it, and at the same time, all of rest of the servo amp's electronics, as well. (One of the things we make here is electronic PCBs, so we have the supplies and equipment to do that properly.)

I then rough bench-tested the power supply with no load. Most of the outputs appeared nominal, including the 5V. However, the 24V was sagging to about 17V with no load. This raised suspicion, but I'm not familiar with this particular power supply. I am aware of others that do not provide nominal power without some specified minimal load. Since I was focused on the 5V anyway, I decided to reinstall the PS and give it a final whirl before ordering a new servo amp.

Surprise! Amazingly, the servo amp now appeared to start up normally, with the Status LED display no longer blank, but reading "-" (not ready), as expected. However, on E-Stop reset, Status LED became 8 and the 414 alarms reappeared.

I disconnected the X-axis motor leads from the servo amp, thinking if there truly is an overcurrent through the motor, this would clear it. But on startup, the alarms and Status appeared the same as before. I then disconnected the A-axis (turret) motor leads, and tried starting again.

This time, though, as soon as I hit E-Stop Reset, the carriage, which had been sitting at home, suddenly fell all the way to the bottom of its travel, slamming into whatever prevents it from falling out of the machine.

That's where I am now. Obviously, I need to get the carriage back to within it's normal operating range. What's the correct procedure for this?


Oct 29, 2010
Dewees Texas
I would copy and paste your info to the CNC section. Not as many CNC subjects are discussed here. I have posted this suggestion before and someone will pop in with an answer. So after you post in the CNC section check here also in case some one replies here with helpful info.