Confused about LinuxCNC and Fanuc Redcaps on a running machine

Which Pico kit do you mean? It seems that you already have a set of Mesa cards and the original amps.

Also, the tachogenerator servo will be perfectly OK with LinuxCNC as long as the drive has a tacho input. Alternatively you can probably just ignore the tacho and control on encoder-only

toolmaker69 wrote:

1. I thought I needed some kind of kit to translate the Fanuc encoder output to something the Mesa card would understand. Is that not correct? Or is that just when using non-Fanuc amps?

It depends on what type of encoder it is. The 4-channel commutation + quadrature type can be used with a normal encoder counter for position and the bldc HAL component can use the 4-channel commutation signals for motor commutation.
If you are using Fanuc drives then it might be that the drives themselves interpret the commutation signals.
If the motors have the Aa64 serial encoders (or similar) then there is a module for the Mesa cards that interprets the data and retains the absolute position information in to HAL. I _think_ that the Pico converter for serial encoders only converts to quadrature and index, so you lose the absolute data. I might be wrong.

2. I thought one should never run tacho-generator servos without tacho feedback. I have lots of tacho-generator servo motors around. Could I put them on the rotary tables, or even use them for a 3 axis mill without using the tachogenerators?

You should certainly not run them with a velocity-mode drive that expects tacho feedback, but if you had that then you wouldn't be asking the question, I assume. If the motor speed / position loop is closed some other way (typically an encoder) then you can ignore the tacho.

3. If I was ignorantly reading threads that were based on just using the motors and not the Fanuc drives, then is it pretty easy to just find the PWM inputs on the drives and run the machine from there?

That slightly depends on which drives, and how many PWM channels you need. I am terrible with names and this is a new thread, are you the chap who already knows that he needs 6 PWM channels?