Mesa 7I96S and closed loop/linear scales

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23 May 2023 22:00 - 24 May 2023 01:37 #272059 by buildmycnc2023
Hi,
I plan to build a 3 axis CNC mill with a Mesa 7I96S.

I would like to use linear scales to create a closed loop.

Should I use - 
A - NEMA's with built in encoder feeding back to the stepper driver and linear scales feeding to the 7I96S.

B - NEMA'S without encoders and linear scales feeding to the stepper driver.

C - NEMA'S without encoders and linear scales feeding back to the 7I96S

D - None of the above!?

Thank you.
 
Last edit: 24 May 2023 01:37 by buildmycnc2023.

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31 May 2023 11:30 #272549 by andypugh
You will need more than just a 7i96S if you want linear-encoder feedback to LinuxCNC as the 7i96 only has a single encoder channel (generally intended for use by the spindle). Maybe a 7i85 or 7i85S on the 7i96 expansion connector.

Linear scale feedback to LinuxCNC can be used to compensate for machine backlash, deflection and nonlinearity. If integrated into the drive encoder feedback on the motors can be used to control motor position and intelligently control the drive current.

So, ideally I think you might want to look a the integrated closed-loop stepper motors (and just let them do their own thing with the motor encoder feedback) and then use the scales to modify the position commands sent to the drives based on the actual measured position.

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31 May 2023 11:52 - 31 May 2023 11:55 #272552 by besriworld
My advice is forget about stepper motors. There are "cheap "AC or BLDC servo motors. And let the driver take care of the exact position. If you need higher precision and the mechanics allow- buy line encoders and mesa expansion board
Last edit: 31 May 2023 11:55 by besriworld.

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12 May 2024 22:21 #300475 by linuxcnc4less
The following user(s) said Thank You: Clive S

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