First Retrofit

Steinj wrote:

I've been looking at Mesa and was thinking about using a 6I25 with two 7I78s would this setup have the capability to accomplish what I want? Additionally, it appears that the 7I29 will drive two 2kw servos but I don't see anything for larger servos, any suggestions for driving a 3-4kw servo?

The 7i78 is a step-dir board for stepper motors, though it can be used to drive some types of servo drive. However it does not offer enough encoder channels for the proposed linear scales. The more common option for a servo system would be the 7i77 . You could alsoconsider the Pico option.

The 7i29 is for DC brush servo motors. However it belongs to a different product "family" to the 6i25. You would need to use a 50-pin header card such as the 6i24.

There is the 8i20 for 2.2kW brushless motors, if you prefer brushless. That connects via yet another interface, smart-serial, and requires either a 7i44 (50-pin) or 7i74 (DB25) adapter board.

A common option for servo-drive control is the Granite Device Argon . I believe that this works well with the 7i77 but is rather too small for your requirements.

if you do not already have the motors and 1.8kW will work for the axis motors then you could look at the DMM motor and drive combinations . The Dyn-4 drive outputs sumulated quadrature for LinuxCNC consumption.

For a 4kW drive I think I would be looking on eBay. Any 4kW drive is likely to be rather expensive. AMC might have something useful , or perhaps a CT Unidrive.

Steinj wrote:

Thanks for the feedback, it looks like I was a little off base. I think I'm going to go with 8I20 and 7I40 for 2kw brushless servos. The 7I40 appears to be compatible with 4I34M, 4I38, 4I65, 4I68, 5I20, 5I22, 5I23, 7I43 and 7I60. What would you suggest? And what else would I need for 6-8 encoder inputs total and limit switches?

Do you really mean 7i40? That's a 400W brushed motor driver.

Do you have the motors already? I would suggest starting there and working backwards towards the PC, so motors, then drives, then we can work out what interface hardware you need.

Steinj wrote:

I'm pretty set on 2kw brushless servos; I just haven't settled on a make and model and wanted to make sure I could get a set-up to drive them before I bought anything. I've been looking at the SVM-220 and the TSB13202B , but I'm open to suggestions

It might be simplest to buy motors with matched controls.

Neither of those links gives much away as to the feedback that the motors provide. (I couldn't even find links to connector pinouts to get a clue).

The 8i20 is cheap and very "dumb" which suits LinuxCNC but you do need to set it up to commutate in software. This works well, but does need a fair bit of knowledge about the motor and the feedback.

What do you know about the connections on the Siemens motors?

I can't really interpret that very well, other than the brake, power and thermistor connections. It looks like it might have a three-phase tacho-generator (which I have never seen before). Perhaps that gives commutation information?

And there isn't much indication what the encoder pins are, but it does look like a simple quadrature encoder.

Steinj wrote:

If I were to inquire with vendors what would I need for the the servo to be compatible with 8I20?

How much do you know about brushless motors?

The 8i20 has a serial data interface to LinuxCNC. That tells it what angle the motor rotor is at and what current to supply.
To be able to transmit this data LinuxCNC needs to know the motor rotor (electrical) position, in absolute angle relative to the nominal motor-zero.
(motor-zero is defined as the position that the motor moves to if the U (or A) phase is energised with +V and the V and W (or B and C) phases are connected to -V)
For a multi-pole motor there will be mutliple zero positions, but they are all equivalent electrically.
There are many ways that LinuxCNC can get this information, but the easiest to integrate is quadrature + hall sensors.
My motors use resolvers, which give absolute position feedback, which makes things slightly easier, but I still had to do a fair bit of experimentation to get it all running.

Bear in mind that the 8i20 needs a DC power supply.

Alternatively, if I got a paired servo and driver would that be compatible with pretty much any controller set-up or is the entire system based on the servo?

It would certainly ensure that the motor and drive are compatible and will save you worrying about things like motor alignment and initialisation. If the drives take AC line power then this also saves you building a power supply. For simplicity look for drives that can accept +/-10v control signal. There are other options, and if you find a deal on something else, we can discuss how to run it with LinuxCNC. But old-school +/-10V is well undestood and supported.

If you don't mind buying second-hand from an unknown source half-way round the world then you could look at ebay, for example
www.ebay.com/itm/251208039716

But I have not done any research on that drive / motor and I can'r see the motor connectors in the photo.