Japanese style spindle orient, how to?

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16 Dec 2022 22:29 #259681 by JR1050
I have a dead Yaskawa spindle drive, the machine has a lame old control. Time to upgrade. I plan on replacing the spindle drive with a Hitachi, problem being the original drive has an “ orientation card” that provides spindle orient. The card watches a magnetic sensor which yaskawa calls a magneto. The spindle has a magnet mounted on it. 

  How would one recreate this as a hal component? It is not an encoder. Obviously the drive runs the spindle at a slow rpm and waits for the sensor to change, but there is more to this, there is no encoder and the original drive has some complex circuitry that allowed for adjustment for the stop angle.

There is no way I see to add an encoder, the gears can shift at any given place. 

Anyone whip this one yet ?




 

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17 Dec 2022 05:27 #259710 by Henk
It will not be trivial to integrate the current magnet and sensor into linuxcnc. In fact, your original control doesn't know about it either. It simply sends a digital signal to the drive and the drive performs the orientation on its own.

You can keep the drive and sensors as they are and use it the same way with linuxcnc.

If you are going to replace the drive, you should go for a proper spindle drive with closed loop control and an orientation function built in.

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17 Dec 2022 05:49 #259712 by spumco
If you're planning to use a WJ200, it has an internal homing (and simple positioning) function along with native encoder input terminals.  You'll need an encoder, but no add-on encoder board.

Maybe a shot-pin & disc on the spindle?

LCNC sends a digital signal to the Hitachi to drop the max current (to bare minimum), fires an air-powered, spring-loaded shot-pin, and commands a slow speed.

Another sensor (proxy?) sees the shot pin drop in the place and LCNC stops commanding the Hitachi to rotate.

All of the above can be set up in HAL using digital i/o (motion.digital-out.nn), and those are available via G-code.  A macro/subroutine named Mxx could run the g-code to orient the spindle.

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17 Dec 2022 05:51 #259713 by spumco

There is no way I see to add an encoder, the gears can shift at any given place. 

 


You got pics or a diagram?  Maybe the hive-mind can come up with an encoder mount.

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17 Dec 2022 19:09 #259759 by cakeslob
I had to look up what a magneto was in a sensor context. looks kinda like it can be used like an encoder depending how it was orientated

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18 Dec 2022 01:40 #259795 by spumco

I had to look up what a magneto was in a sensor context. looks kinda like it can be used like an encoder depending how it was orientated
 


Is it another term for a resolver?

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18 Dec 2022 11:17 #259814 by mwc
I'd guess the 'magneto' at the actual sensor level is either just a reed switch, or a hall effect sensor.
The complicated bit would be getting the spindle to stop under control at the required angle, especially if there's gearing involved.

If it's a simple case of stopping at the magnet, you just need to rotate at a slow speed and stop the spindle motor.
If however you need to stop at x degrees after the magnet, then things get quite a bit more complicated, but should be doable.

 

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18 Dec 2022 15:37 #259826 by JR1050
The magneto is not a resolver. It’s a magnetic sensor.

Replacing the drive with another drive that uses an orientation card is not remotely economically feasible. In addition to using a magneto for position sensing, the original drive used resolver feedback for speed sensing. Replacement equivalent is a 626 M5 , about 15k. I’m presently repairing the mk2 drive, again... 

While there is no place to put an encoder on the spindle itself, I can put an encoder in place of the resolver on the motor. This would give me the ability to count pulses , either the magneto could be used to find the initial orient position or it could be replaced with a hall type switch . After the switch has been first sensed, the drive can be instructed to run until the control counts the amount of pulses, which would be an offset amount, from initial position sense to actual position , then apply the brake. Since it’s an incremental amount, the encoder doesn’t need to be on the spindle itself. 

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19 Dec 2022 13:10 #259888 by spumco

 After the switch has been first sensed, the drive can be instructed to run until the control counts the amount of pulses, which would be an offset amount, from initial position sense to actual position , then apply the brake. 


If your magnetic trigger doesn't work for you, I've had good luck with a plastic ring on a spindle using a set screw to trigger an inductive proxy.

I think you'll be better off leaving the homing inside LCNC even if your VFD has an internal homing function.  Assuming you set things up with motor encoder and spindle index sensor, I suspect you'll need a mux component to select from a number of different encoder count offsets depending on which gear you're in at the time of homing.

I think there are a number of gear indicator or change schemes described in the forum.  I'm not sure of the details, but I think LCNC can be set up so that the encoder counts are logged between index pulses, and a look-up table is consulted to determine which gear ratio has been engaged.

Once the current gear ratio is determined, a second look-up table is used to set the appropriate encoder count offset from the index signal during homing.  I suspect that the sequence would require the spindle to turn at least two revolutions to home: one to calculate the gear ratio, and a second to do the index-then-offset move.

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19 Dec 2022 23:50 #259913 by andypugh

While there is no place to put an encoder on the spindle itself, I can put an encoder in place of the resolver on the motor.


If there is a gearbox in the way then this wouldn't help. Also, are you sure that the spindle drive doesn't need the resolver to commutate? I like resolvers, in caft I only have one encoder in my workshop, on the Harmonic drive. All the other motors and spindles are on resolvers.

I don't see how it could ever be possible to stop at a position some fixed angle after the magent pulse without some sort of extra feedback. (unless it used the motor resolver and knows which gear it is in. and/or can worl out the gear from the reolver position and the magnetic pulse time.

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