Retrofitting a MAHO MH500W '89-'90 with hand-feed

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21 May 2023 14:29 #271825 by PCW
If these are velocity mode drives, you must have FF1 for decent performance
Note that if you scale the analog output to the drives machine velocity in
units per second at 10V, FF1=1.0.

If you leave the default scaling of 10 (= scaling in volts), FF1 =
10/drive_velocity_at_10V

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21 May 2023 15:44 #271836 by petmakris

If these are velocity mode drives, you must have FF1 for decent performance
Note that if you scale the analog output to the drives machine velocity in
units per second at 10V, FF1=1.0.

If you leave the default scaling of 10 (= scaling in volts), FF1 =
10/drive_velocity_at_10V
 

I suspect that I have a velocity mode amplifier (It's an Indramat 3TRM3) because I have applied constant voltage and it was moving at constant velocity. Can you explain how to tell if it's a velocity or torque driven servo system? I can't find any information anywhere for this.

Another thing, which parameter has a default value of 10? is it the OUTPUT_SCALE from the INI file? because this defaults to 1V.

I just some other post you said

For velocity mode PID use I like to set scalemax to the drives machine units (inches or mm) per second at 10V in. This normalizes the PID loop so FF1 can be set to 1.

Which parameter is this scalemax? Can't find it 

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21 May 2023 15:47 #271837 by petmakris
Let's try and be a bit more specific:

My machine has a maximum velocity of 2 meter / min = 33.3 mm/second.
Which value should I configure as 33.3 so then the output is normalized and I can set FF1 to 1.0

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21 May 2023 16:29 - 21 May 2023 16:57 #271847 by petmakris
Another thing that confuses me is that, as is, it moves with a 2000mm/min velocity at 10V.  How can the product manual say the machine had 4meter/minute rapids?

 

It has 4meters in X,Y  and 2meters in Z (maho Y is normal Z)

I just measured that moving at 500mm/min takes 1.15V for X and Y while the on Z takes 2.3V
Attachments:
Last edit: 21 May 2023 16:57 by petmakris.

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21 May 2023 16:55 #271851 by PCW

Let's try and be a bit more specific:

My machine has a maximum velocity of 2 meter / min = 33.3 mm/second.
Which value should I configure as 33.3 so then the output is normalized and I can set FF1 to 1.0? 
 

The PWM scale value

One way of looking at this is If the PWM scale value is 33.3 a commanded velocity
of 33.3 mm/sec will result in full scale PWM
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21 May 2023 20:08 #271875 by petmakris
I managed to find a set of values with sweet performance.
Last values on repository (links above).

Normalizing the scale output did not work for me, I was getting huge following error in velocities > 500mm/min.
 

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21 May 2023 20:32 #271880 by PCW
Well, normalizing will work but you also have to make sure the PID maxoutput does not limit the output... (and the FF1=1.0 is only as accurate as you speed measurement at 10V)
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21 May 2023 21:01 #271882 by joekline9
You need a value in FF1.
Keep increasing the value until f-error goes on the other side on zero. The back off until it stays close to zero.
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21 May 2023 21:52 - 21 May 2023 21:54 #271883 by petmakris

Well, normalizing will work but you also have to make sure the PID maxoutput does not limit the output... (and the FF1=1.0 is only as accurate as you speed measurement at 10V)


I assumed something like that but I did not have the energy required to keep digging.

Finally, I decided not to do the scaling and play with FF1 such that f-error gets minimized (starting from 1.0 / vel at 10V).
Last edit: 21 May 2023 21:54 by petmakris.

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26 Jul 2023 06:24 #276291 by zopf96
Hi Petros,
I have the same machine at home and thinking of converting it to linuxcnc as well. What is the current status of your project? Could you give me tips on how to start and what to look out for?

Thanks for your reply :)

Kind regards
Christoph
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