Gerber 408 retrofit

27 Sep 2022 01:20 #252818 by MKMII
Gerber 408 retrofit was created by MKMII

I am working on retrofitting a late 90's Gerber Sabre 408 with LinuxCNC.  The PC that was running Gerbers proprietary software finally died so I decided to move to LinuxCNC.

My setup:
Mesa 7i96s
3x Gecko G320x servo drives
Original servo motors (Parker RX320ER1026)
Original Encoders (Renco 324599-03)

I got the software loaded, rewired everything (Gerber didn't make this part easy), Got the VFD changed to take a 0-10v signal, etc.

Where I am stuck is on the X, Y, Z configuration. Originally I used the Gecko 320 configuration from the drop down in the pncconf because I fugured that the "x" shouldn't change much. There was motion but not the distance I expected. Then I found the settings for the G320X and that provides no motion of the motors.  This is my first build and I feel so lost when it comes to setting up the servos.  I have no clue what the encoder counts are, how many steps per revolution, etc.

Any help on dip switch / software settings on this would be much appreciated.    

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27 Sep 2022 02:24 #252822 by PCW
Replied by PCW on topic Gerber 408 retrofit
One thing to remember on step length settings is that the manufacturers numbers are
_minimum_ values so these should not be used in a real system. Unless it interferes
with the maximum speed, I would start with values double the manufacturers minimums.

As far as scaling goes, if you know the ball screw pitch, the number of steps per turn
and any gearing between the motor and the ball screw, this can be calculated. If you dont have this information you can determine it with successive approximation (as long as you have good measuring tools)

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27 Sep 2022 02:37 #252825 by MKMII
Replied by MKMII on topic Gerber 408 retrofit
So, if I understand correctly, the step on time, step space, direction hold, direction space should be doubled as a starting point?

I found this info online and believe that it may be accurate:
for the X, and Y axis which should allow me to calculate my scaling.
servo encoder counts per revolution: 4000
Servo teeth: 28
Lead screw teeth: 70
Pitch: 20mm
counts per mm: 500

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