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Author Topic: spindle encoder, VFD, rigid tap, lathe  (Read 8779 times)

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spindle encoder, VFD, rigid tap, lathe
« on: October 29, 2009, 12:16:52 AM »
Hi All,

I am working on a lathe retro-fit and have a few questions about spindle feedback in Mach.  I currently have a little lathe running now on Mach with just a spindle index for feedback into Mach, one pulse/rev.  The spindle motor/drive is a cheap 3HP hitachi, no feedback into the drive.  It works amazingly well for cutting threads...

The big lathe I am working on now has a 15HP DuraPulse Vector drive with the encoder feedback option.  There is a quadrature encoder with an index pulse on the spindle that spins at the RPM of the chuck and there is an auto lo-high in front of that.  I was considering just running the spindle's encoder to the feedback card in the DuraPulse, and the index pulse to Mach3.  I have a few questions about the setup:

1- Is rigid taping on a lathe an option in Mach?
2- Can/should the encoder go to just Mach, just the drive, or both?
3- This is probably more of a question for automation direct, but how will the drive work with encoder feedback after a gear-shift?  I may need to change the way I command the spindle speed based on the ratio between the motor and the drive....  Anybody out there done this?

I am going to try to post some pictures of the machine in the "show'n tell" section if anyone is interested...
Thanks!
Dustin


Offline Hood

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Re: spindle encoder, VFD, rigid tap, lathe
« Reply #1 on: October 29, 2009, 04:04:11 AM »
1- Is rigid taping on a lathe an option in Mach?

No its not an option as such, if you have a servo as a spindle motor then you could  use SwapAxis and change the spindle to the A axis, this would then allow rigid tapping, it would however require that their is no backlash in the spindle setup. You can use a floating holder and do semi rigid tapping.

2- Can/should the encoder go to just Mach, just the drive, or both?
Encoder will just go to the drive, the index pulse may possibly be used for Mach but that will depend on what hardware you have, if just using the parallel port then it will probably be too short a pulse for the parallel port  to see. If using external hardware such as the SmoothStepper then you can use the encoders Index pulse.


3- This is probably more of a question for automation direct, but how will the drive work with encoder feedback after a gear-shift?  I may need to change the way I command the spindle speed based on the ratio between the motor and the drive....  Anybody out there done this?

Not really sure how your gearing works but it will more than likely not be a problem for the Automation Direct drive as it will still be rotating the spindle in the same manner, it will be your SpindleSpeed macro that will need to call things correctly.

Hood
Re: spindle encoder, VFD, rigid tap, lathe
« Reply #2 on: October 29, 2009, 11:57:20 AM »
Thanks Hood, I realized shortly after posting that a little reading on the rigid taping would've answered that question, I will look into floating tool holders, or just cut the threads with single point tool.

On the gearing in the spindle, there is a high and a low range that is shifted hydraulically via  a solenoid valve.  There are switches that sense lo, hi, and neutral.  The encoder is after the gearshift, so the ratio between it and the motor changes upon shifting.

Dustin

Offline Hood

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Re: spindle encoder, VFD, rigid tap, lathe
« Reply #3 on: October 29, 2009, 02:33:15 PM »
I am not sure how your DuraPulse drive works but I would imagine if it is using an encoder to keep the speed more constant then you will likely need to drive the encoder 1:1 with the motor. I am presuming the encoder will be true RPM so that is fine as far as Mach is concerned. If the encoder settings can be set dynamically within the drive then you could use Mach to signal the change to take place but that is probably unlikely.

Hood