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Haas SL 20 Lathe spindle overload

Flathead26

Plastic
Joined
Oct 22, 2023

Need help on our 2008 Haas SL20 TB lathe.​

The trouble all started when we changed the motor pulley.​

We were testing it at 500 rpm for a few minutes then ran it up to1500 rpm.

A few minutes later, there was a pop and we found that the drive had failed.

Since then,

  • the drive has been repaired and tested twice,
  • the motor has been cleaned,refurbished and tested
  • the motor connection block has been tested and cleaned
  • the motor encoder has been tested and repaired
  • the Wye Delta contractors have been replaced
  • the Haas tech was here 5 hours
and still when the spindle is commanded to run 500 rpm it runs at 17 rpm

and has a 200% power draw. HELP ! ANY IDEAS ?
 
That one is a stumper of a problem, considering Haas was already there for five hours. How comfortable are you dealing with multimeters around high voltages? You're aware the capacitors in the Vector Drive will hold a charge after shutdown, right? Wait until the red LED goes out before touching any of the screws. Check with a voltmeter to be sure.

Why was the pulley replaced? Did they remove the motor during that service? Could a wire bundle have been pinched against a casting in there? Were the wiring connections in the motor monkeyed with? I don't know what the motor wiring looks like on these but, I'd be suspicious about the wiring if the connections were undone and reconnected. The wye-delta thing could be cross wired wrong or something.

Where was the pop heard? Cabinet behind the machine? None of the magic smoke escaped? No other errors in the control, other than the 200% load and wrong speed?
 
That one is a stumper of a problem, considering Haas was already there for five hours. How comfortable are you dealing with multimeters around high voltages? You're aware the capacitors in the Vector Drive will hold a charge after shutdown, right? Wait until the red LED goes out before touching any of the screws. Check with a voltmeter to be sure.

Why was the pulley replaced? Did they remove the motor during that service? Could a wire bundle have been pinched against a casting in there? Were the wiring connections in the motor monkeyed with? I don't know what the motor wiring looks like on these but, I'd be suspicious about the wiring if the connections were undone and reconnected. The wye-delta thing could be cross wired wrong or something.

Where was the pop heard? Cabinet behind the machine? None of the magic smoke escaped? No other errors in the control, other than the 200% load and wrong speed?

Thank you for your response. Im Ok with the mulitmeters ,high voltage and am familiar

with the capacitors.( thank you for thinking about my safety) The pulley was replaced because of belt chatter. A tech guy that we use removed the wiring for testing. We have looked at the wiring connections, and compared them to the Haas wiring diagrams multiple times. I wasn't there when the pop happened, but I know that at least the drive failed. I have looked at the boards, but don't see any sign of damage. The Haas guy said that it was the encoder or the Wye Delta contactors. The encoder was reworked and the contactors were replaced, still same result. I haven't seen any error codes,except for the overload. I am not a tech, but Haas literature mentions the IO board often, so I thinking of running some tests, as per their prescribed instructions, but I think the Hass guy checked that, while he was here.
 
I have a 2007 SL10 with a single spindle encoder. I believe your SL20 is a dual encoder machine. Either way, it sounds to me like your encoders are not properly relaying the correct spindle rpm back to the main board. On my SL, if the encoder is not turning 1:1 with the spindle, the lathe will sense an overload condition and the drive will ramp up the spindle motor power. If you leave the motor running in like that for very long you could indeed blow the drive. The over load meter will also be pegged at 200%. If this occurred after a pulley replacement I would first make sure both encoders are mechanically spinning 1:1 with the spindle motor. Some one might have forgotten to lock a grub screw on the encoder. If the mechanical connection is solid between the encoder and spindle shafts I would then confirm that both encoders are properly connected to the wire harness. With the servos on but the spindle off, if you turn the spindle by hand, does the rpm appear to read correctly on the console? Go after the obvious things first…I would look at the encoder near the pulley you just changed.
 
I have a 2006 SL30 and the set screw did loosen up on the encoder so that's definitely worth checking.
 
I have a 2007 SL10 with a single spindle encoder. I believe your SL20 is a dual encoder machine. Either way, it sounds to me like your encoders are not properly relaying the correct spindle rpm back to the main board. On my SL, if the encoder is not turning 1:1 with the spindle, the lathe will sense an overload condition and the drive will ramp up the spindle motor power. If you leave the motor running in like that for very long you could indeed blow the drive. The over load meter will also be pegged at 200%. If this occurred after a pulley replacement I would first make sure both encoders are mechanically spinning 1:1 with the spindle motor. Some one might have forgotten to lock a grub screw on the encoder. If the mechanical connection is solid between the encoder and spindle shafts I would then confirm that both encoders are properly connected to the wire harness. With the servos on but the spindle off, if you turn the spindle by hand, does the rpm appear to read correctly on the console? Go after the obvious things first…I would look at the encoder near the pulley you just changed.
Thank you for your reply. The pulley that we replaced is the same diameter as the original. My Sl20 has an encoder on the spindle and the motor.
I did replace the encoder pulley on the motor. but I think it has to be right, because I also bought a new belt with the same number of teeth and everything went right back together. I will defiantly check the grub screw on the encoder. I have turned the spindle by hand and I am getting an RPM reading.
I pulled the cable from the motor encoder and immediately got a cable error code, so it seems like the motor encoder is supplying feedback to the control.
The encoder on the motor was checked and reworked. I am wondering if the one on the spindle could have a problem and is fighting the one on the motor.
 








 
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