Spindle encoder setup probelms with mesa 7133

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16 Jul 2012 04:51 #21982 by jbunch
Andy,

It looks like you are correct. The "I" works when it is way smaller then FF0. Also top speed on the lathe is 1800 on the plate.

So what does closed loop buy me? I would think that it would be added torque at low RPM's. Other then that I am not sure.

Can you gain enough torque to to run the spindle at 90 RPM and motor at 180 RPM and still make large cuts?

would that require a larger motor say 7hp instead of the 5 I have?

If so then the next project is to direct connet the motor to the spindle and bypass the gearbox.


Jim

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16 Jul 2012 09:32 #21986 by andypugh
jbunch wrote:

It looks like you are correct. The "I" works when it is way smaller then FF0. Also top speed on the lathe is 1800 on the plate.

Something seems a little odd, then.
Assuming S1800 your FF0 term comes out at .0036. Which is presumably full-scale on the PID input.
That "36" looks suspiciously like a 3600. I wonder if there are a couple of inverted 60x scalings in the system?
(Some things are in rpm and some in rps in HAL)
Not that it matters, the computer just sees numbers and treats them all the same.

So what does closed loop buy me? I would think that it would be added torque at low RPM's. Other then that I am not sure

It means you have the cutter surface speed you asked for regardless of non-linearities in the system.
With a DC motor or a servo it will also give you much higher available torque at the set speed. You get some of the same effect with an induction motor, but not to the same extent.
This has set me wondering about setting up closed-loop spindle on my lathe, though, as it might help with parting. (The Mill already has it)

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