How to setup gearbox/reducer

Hello,
I have AC servo motor which has harmonic gearbox with ratio is 80:1
How can I setup LCNC to work correctly with the gearbox ratio ?.
Thank you.

Depending on if your a controling your servo closed loop or open loop in Linuxcnc. You have to calculate the encoder counts or steps per unit of measure that you wish to use with this joint. The units could be inches, mm or other if the joint is linear, or if the joint is rotary the units would be degrees, radians, revolutions, or other.

If for example this joint is for a rotary C-axis in degrees and your servo motor is closing the loop to Linuxcnc with a 2000 line encoder directly coupled to the motor and the motor is directly connected to your 80:1 gearbox. You would use 2000(4)*80/360=1777.777778 counts/degree. So in your ini file you'd put ENCODER_SCALE = 1777.777778

You did not give us enough info to be able to help:
-what is the motor driving
-how is that motor coupled to the machine
-how much does the machine move for one turn of the reduction
etc.

Hi Tommylight,
My system is:
- Drive: AC Servo EtherCAT drive
- Motor is installed in SCARA robot
- The encoder: 17 bit optical absolute multi-turn. Its resolution is 131072, so I understand it has 131072 counts for one turn.
- The mechanical gearbox ratio is 80:1, fixed with motor.
Hope it is all you need Thank you.

Hello Todd,
I understand that you make example of "incremental encoder" with quadrature.
My encoder is 17 bit absolute multi-turn type, so the counts for one turn is huge value 131072.
I calculate: 131072*80/360 = 29127.111111. Is it still correct to apply ?.

I put ENCODER_SCALE = 29127.111111 to INI file, but nothing happen.
I understand need to revise HAL file to use ENCODER_SCALE, but it seem encoder component is only suitable to incremental encoder type.
linuxcnc.org/docs/devel/html/man/man9/encoder.9.html

Please advise Thank you.

Looking at my notes on my Melfa robot config using absolute encoders it seems that the value in [Joint_n] SCALE is
360/gearbox_ratio
So for my 80:1 geared J0 I have SCALE = -4.5
for my 120:1 J1 I have SCALE = -3

And so on.

I'm not sure how I came up with that idea but it certainly works for me.