Absolute encoders and Centroid Step per revolution setting

[Proidea]

Hello everyone.
I have an Acorn CentroID Controller and four Panasonic AC Servo, 17 bit absolute encoders on the motors set as incremental. It's a Router with 10 mm lead on X and Y Ballscrews and 5mm on Z.
After having (I think) understood how to set the electronic gear ratio in the Panasonic drivers, the doubt that remains is the following:
How should I set the number of pulses per revolution in Acorn? - the same set in the drives or multiply it by four?

Thanks!!

Henry

[suntravel]

The setting of the servo encoder is for the servo driver only. You must set up the servo in pulse mode and Acorn to the same steps/rev

Uwe

[Proidea]

Thanks for the quick reply: the drivers are set in Pulse mode, everything works and now I would like to set the output from Acorn Centroid and consequently the driver inputs. What do you mean "The setting of the servo encoder is for the servo driver only"? I set the absolute encoders as incremental by modifying the parameters of the Panasonic drivers. Is that what you meant?
Thanks,
Henry

[suntravel]

The encoder of the servo takes only care of that the commanded position is reached. It will not communicate with Aron for the position, except you can setup ZRi homing using one of Acorn inputs.

Uwe

[eng199]

How should I set the number of pulses per revolution in Acorn? - the same set in the drives or multiply it by four?

Most drives use pulses per revolution (PPR) in their setup menus, as you state. Centroid uses counts per revolution. Multiply the PPR by 4 to get the counts per revolution for ACORN.

[Proidea]

Thank you Uwe and eng199 for your suggestions. Unfortunately I still don't understand, also because it seems to me that Uwe says to use the same number, eng199 says to multiply by 4. Or am I wrong?

[cncsnw]

Set pulses/rev to "the same number".

Test it.

If it only moves 1/4 of a turn when it should move one turn, then "multiply by 4".

[Proidea]

Thanks cncsnw,
That's what I'm going to do.

I just wanted to understand how it works.
In other words: how the output of an absolute encoder behaves when it is set as Incremental in the AC Servo driver. Is its output seen as Quadrature output? Does a 17 bit Absolute encoder have the same resolution of a 17 bit incremental encoder?

[cnckeith]

typical steps per revolution settings in the Acorn Wizard for AC servos on Router application is 4096 steps per rev. , then you set the electronic gear ratio in the servo drive so that the servo drives understands that Acorn is going to send it 4096 pulses/steps for one rotation of the axis motor.

then in cnc12 with motors on the bench, set overall turns ratio to 1 (if using inches, 25 if using mm),set home, mark the shaft, go to MDI and type G0x1 and observe..did the motor shaft rotate one revolution? if so, you are good to go. if not, you probably have the electronic gear ratio set wrong.

for further reading on this subject visit this thread.
https://centroidcncforum.com/viewtopic.php?f=63&t=1801

[suntravel]

If you use a Servo for the spindle an it drives the spindle 1:1, than you can try to use the encoder output from the servo driver for the spindle encoder input an the Acorn. But you can not use the encoder outputs for the axis if you use servos to drive the axis with acorn.

Some servo drivers with 17 or 23 bit absolute encoders on the servos can output the quadrature differential signal Acorn needs for the spindle. If you Panasonic can do this should be written in the driver manual.

Uwe