Spindle RPM constant variation than programmed RPM (CNC Turning Lathe)

[creamroll]

Which model Fanuc control? Starting a thread at random is most often a bad spindle encoder on a machine with a Fanuc control.

Fanuc Model OI-TF

 

[Vancbiker]

The mix and match use of a GSK motor and drive with Fanuc CNC will make this a more difficult problem to troubleshoot. My collection of 0i manuals stops at the D version. I’ll see if I can find some F version manuals so I can point you to connections to look for a spindle encoder.

 

[creamroll]

The mix and match use of a GSK motor and drive with Fanuc CNC will make this a more difficult problem to troubleshoot. My collection of 0i manuals stops at the D version. I’ll see if I can find some F version manuals so I can point you to connections to look for a spindle encoder.

Alright! Thanks a lot!

 

[rjwalker1973]

Hi The motor is a GSK GS3000 series model GS3100Y. I've been trying to find the right parameter in it's manual but so far haven't been successful.

I was refering to the variable frquency drive unit. It would be in the control panel and has various settings that will affect the motors behavior.

 

[Jhn3:16]

Is it possible it could be a motor to spindle ratio difference?????

I have never tried adjusting this in SP-SETTINGS screen. But they are usually displayed

Brandon

 

[sinha]

Starting a thread at random is most often a bad spindle encoder on a machine with a Fanuc control.

I think he should first change the encoder, then observe what happens.

 

[Vancbiker]

Is it possible it could be a motor to spindle ratio difference?????

I have never tried adjusting this in SP-SETTINGS screen. But they are usually displayed

Brandon

Since he has a GSK spindle drive, the control is most likely using the analog spindle interface so SP-SETTINGS data will be limited. I don’t know anything about the GSK unit, but think it unlikely that it is compatible with Fanuc serial spindle interface.

 

[Vancbiker]

I think he should first change the encoder, then observe what happens.

Rather than swap part, it would be preferable IMO, to use an oscilloscope and monitor the signals from the encoder.

 

[sinha]

Rather than swap part, it would be preferable IMO, to use an oscilloscope and monitor the signals from the encoder.

He may not have an oscilloscope. Moreover, it may require some expertise to interpret the results of an oscilloscope.

 

[Vancbiker]

He may not have an oscilloscope. Moreover, it may require some expertise to interpret the results of an oscilloscope.

True that we do not know the tools available to the OP nor do we know their level of expertise. That said, now would be a fine time to spend <$100 on a USB oscilloscope to use with a laptop and learn a little bit about analyzing signals on a simple encoder. A replacement encoder will likely have a >$1000 cost.

 

[sinha]

True that we do not know the tools available to the OP nor do we know their level of expertise. That said, now would be a fine time to spend <$100 on a USB oscilloscope to use with a laptop and learn a little bit about analyzing signals on a simple encoder. A replacement encoder will likely have a >$1000 cost.

Good enough motivation to procure an oscilloscope.
Learning is bit by bit only, till one becomes an expert.

 

[rjwalker1973]

Good enough motivation to procure an oscilloscope.
Learning is bit by bit only, till one becomes an expert.

Thats how I have learned. Bit by bit and through mistakes. I tell my younger employees all the time I learned more from making mistakes than any other way.

 

[dandrummerman21]

Or, now hear me out here...

Just leave it be and run it. Sounds like the fanuc knows what RPM it is running, even if the drive doesn't.

If being 20rpm faster than you want it to be kills you, program it to be slightly slower.

If it was making terrible threads? yeah, better dial it in.

 

[Ox]

Actually that's the main issue.. threading is not getting done properly.. every pass starts the threading from a different point and as result forms a new helical..

---------------------

Think Snow Eh!
Ox

 

[dandrummerman21]

---------------------

Think Snow Eh!
Ox

er... hmmm. missed that.... welp. get to fixing!

 

[CarbideBob]

Cutting a thread 2 or 10 passes should be simple like on a manual lathe.
In the cnc world it gets messy to sync those passes.
Outside wild ass thinking, index pulse problem to control.
The spindle encoder should be the master.