Acceleration capability for Fanuc Model 0 motor

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10 Jul 2010 13:53 #3321 by DavidB
Hi everyone,

Do any of you know what the Fanuc Model 0 DC brush motor is capable of in terms of acceleration? I have all the parameters for my current machine and the only paramater I have showing acceleration is for rapid traverse. It shows 150mm msec in acceleration.

For EMC2 purposes I need inches per second squared. Any idea how I can derive that from the parameter shown above? Better yet are there any specs out there from Fanuc listing the maximum acceleration for this motor?

Thank you!

David

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10 Jul 2010 15:42 #3322 by PCW
Are you sure thats an acceleration number? maybe its 150 mm/sec which sounds like a (fast) rapids=traverse number to me

A bare servo motor (like your Fanuc) will accelerate very rapidly, somewhere in the 1000s of RPM in one turn from a dead stop.
While you can get this spec from the motor manufacturer, what you really want however is how fast you can accelerate your axis with
its ballscrew and linear axis inertia + external friction and cutting load

This number would be the ((peak motor torque-(friction+peak cutting torque)) / system inertia) (if my rusty high school physics is right)

The original machine specs should have this number, If you don't have the specs or they are not listed
one possibility is to start low and keep adjusting acceleration upwards until your servo can no longer follow
at maximum acceleration points. Once you have found this point, you will now have to lower this acceleration
setting to allow for additional torque for actual cutting.

If your machine can indeed traverse at 150 mm/sec (around 6 IPS or 480 IPM), an acceleration value of 1 second to max
rapids rate might be a good guess so 6 IPS/S could be used as a starting acceleration value.


my 2c

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10 Jul 2010 20:31 #3323 by DavidB
Thanks PCW.

The parameter that I was referring to is titled "Time constant in linear acceleration/deceleration". The setting for this controller can be between 8-4000 (unit: msec).

After looking at it again I believe I misinterpreted the setting as 150mm per msec. I now think it is saying that the time constant value in linear acceleration/deceleration is 150 msec.

Is this helpful at all in determining the maximum acceleration for my machine?

If not, I can move forward with your example as to how to determine the maximum acceleration.

Thank you!

David

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12 Jul 2010 15:01 #3339 by PCW
Still hard to guess from those numbers...
Maybe you can post what your machine is and someone with a similar machine
can give you a good starting point acceleration value.

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