Apogee

The dreaded electrical problems before Christmas. On our QT20N we had a filter blockage on the electrical cabinet, everything got a little hot. Being a T2 machine they run fanuc spindle drive. Our initial alarm was a 204 controller malfunction along with a 200 thermal trip, the spindle drive was showing an alarm 10(+15v voltage drop). We have had the drive serviced and cleaned, they found the main fans on it had broken as well. This was reinstalled and the machine worked for a few days with out issue before the same 204 and 200 alarms appeared again. The board this time was showing an Alarm 2.It was recommended that we replace the front A20B-0009-053 circuit board which was done but the same alarms are still happening.

The machine will power up fine and you can manual start the spindle, ramp it up to 1500rpm with no issue, if you stop the spindle and try to restart it at 1500rpm it will alarm out, it does not like a high draw on it?

Does anyone have any ideas of where to look next?





On one of the times this thermal overload and contactor was buzzing and behaving badly, it is the thermal overload for the drive. Not sure if this could be faulty but it does not trip out when the drive goes?

The “MOT” contractor and overload relay are for your hydraulic pump.

Sounds like your Fanuc drive needs new base transistors (IGBT’s or Darlingtons), since that’s what Alarm #2 says is faulty.

If you’re handy with a screwdriver, you can disassemble the drive base and replace the base transistors yourself. You can source these from Fanuc, or cheaper on EBay.

Good luck with it,

ToolCat

Thanks, we have changed those on some of our other machines, the fanuc guys gave the drive a clean bill of health but it looks other wise from your suggestions!

I take it that theses are the ones I need to change 4-K3?

I’m not familiar with Fanuc spindle drives (Mazaks usually have Mitsubishi drives), but the “accel and run” (inverter) IGBT’s are on the right side, with the large output wires feeding the terminal block that feeds the motor.

The drive either won’t run the motor, or alarms out when accelerating—when the inverter IGBT’s go bad.

The center power transistors are for “decel” (converter) functions, and the drive will alarm-out when stopping if these are bad.

There are test procedures for the IGBT’s, although sometimes they have to be out-of-circuit to get true readings from your multi-meter.

Give Tennessee Industrial Electronics a call, they are probably better at diagnosing and repairing older Fanuc stuff than Fanuc is!

Good luck with it,

ToolCat

Thanks for the suggestions, got some IGBT's (the right ones I think) on order and will have a go at changing them, I have repaired most things on these lathes but never a drive.
The lathe is a good old T2 version, it must be one of the ones built before Mazak gave up on Fanuc and went to Mitsubishi. The machine currently has this 9" billet on it and due to customer pressure I played around with running the roughing part of the job, the machine spent two and a bit hours pulling 60% spindle load with no issues or faults, the drive alarms seem to be only when running in the higher rpm's, do you think this still points to the IGBT's or some perhaps some other part of the wiring?


On other projects, I have been looking for the right size gantry crane to service some of the machines for loading billets, changing pallets and maintenance items, using a forklift or engine crane gets boring quite fast. Came upon this 3.2 Abus that will fit perfectly in one of our units. 10 meter span, 20 meters of runway. Spent a couple of days dismantling just before Christmas.





The plan hopefully is to move around some machines so we can get the big VTL, Horizontal and a couple of the bigger lathes and VMC's under it.