Does Linux CNC support Closed loop with Steppers?

tommylight wrote:

The only issue is when using closed loop stepper/drives and using the same encoders for LinuxCNC feedback ( even this will work for sure ) but might need some signal shaping and/or splitting to have the same encoder wired to two inputs on the drive and Mesa board.
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This is something I have been looking into, my robot does this with its oem drives and has cables that go from the servodrives to the motion control card sending the encoder signals. So I have been looking for drives that do that aswell, and have found some of the lichuan drives do this servo.xlichuan.com/ProductsStd_212.html
Im not sure what the benefits would be for a cnc though with incremental encoder

Thanks everyone,
This has been a great help to me. Sorry if I ask any stupid questions. I starting from 0 knowledge. I just always wanted a CNC and I like building things. so I thought I would build a CNC what could go wrong?

Hakan wrote:

Don't know if linuxcnc officially supports it but I have it, use it and it works great.
The 7i95 should work but I guess the guy didn't have that one since he tried to sell you a 7i96.
The 7i96 should work together with a 7i85 for encoder input. The 7i76e + 7i85s is what I have
since a couple of years and yes it works fine, wouldn't use the milling machine without the linear scales.

Hakan, is it possible for me to have a look at your ini and hal files for this setup? I've recently bought a 7i96/7i85s combo but don't know where to start with using the linear scales for feedback.

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Para que se pueda usar los encoder de los motores de ciclo cerrado tanto para sus controladores como para linuxcnc como sería?

No idea what drives you're using but most servo drives have an encoder output. So you connect the physical encoder to the drive, then the drive emulates the encoder output and you connect that to the motion controller. As mentioned it's not wise to try to split an encoder signal but Mesa used to sell an "encoder Y" board that splits the encoder into 2 outputs if you really wanna do it.

That said I don't really see the point. The drive itself is closing the feedback loop so the controller doesn't have to. It should be sufficient just to command the drive and just wait for the output signal that says "I didn't do what you told me to"

You could get some benefit from using they closed loop stepper as it's meant, but also adding another encoder to the axis and feeding that back to LinuxCNC. For example, if your doing a Mill you could couple an encoder to the end of the screw on the opposite end of the table. That way if the motor coupler slips, the closed loop step drive won't catch it since the motor did spin, but the other encoder on LinuxCNC would see it.

Muchas gracias por la respuesta realmente lo pensé para cuando lo uso manual como si fuera convencional, y no cnc, poder usarlo como especie de regla óptica para saber cuánto avance,por ejemplo , estoy haciendo un trabajo rápido a mano q no es cnc un simple cilindrado pues dejo los motores apagados para poder girar manual entonces cojer la señal del encoder y saber cuánto le di de profundidad exactamente, no sé si me haga entender pero igual agradecido