Something like this has to exist already

[turbo2ltr]

I have an older 3 axis VMC that uses Servopack CPCR-MR drives and a Yasnac MX1 controller. The controller is pretty limited, I mean it does the job, but for instance it does not support helical moves and it has to be drip fed because I can remember more lines of code than it can. I wrote my own drip feeder which works well, but what I'd really like to do is use Mach 3.

So after digging in some poorly scanned docs and probing with a scope, I think I understand how these drives work. I was hoping that it would be easy to interface mach3 with the drives, but the drives take in a speed reference, and that's about it. It looks like the tach goes to the MX1 so without the MX1 there is no chance of using pulses to drive the servo without additional hardware.

So I'm thinking through what I would need to build (I'm an EE) to interface the two. mach3 takes care of a lot of the stuff that the MX1 would normally handle (such as ramp rates, etc) so the interface between the two would only need to take the pulse train and "match" it with the tach signal, and adjust the voltage to the drive accordingly to maintain the commanded position.

The more I thought about it, the more I thought that there has to be something like this already but I'd have no idea what it's called. Has anyone ever heard of anything like this? If not, has anyone ever wanted something like this or am I the only one dumb enough to think this is possible?

[Al_The_Man]

You probably would be better off using the same motors with off the shelf step direction drives that are compatible with mach, you would not need the tach.
The loop would be closed by the encoder back to the drive.
One of the set backs to your system is the fact the tach goes back to the controller whereas it usually goes back to the drive.
If they had, then all you would have needed would have been a step/dir to analogue converter.
Al.

[turbo2ltr]

Thanks for the info. I'm guessing we are talking well over $1000 for 3 axis worth of drives?

[turbo2ltr]

Can anyone tell me what "TG" might stand for?

[mike_Kilroy]

from flavor of this string I would say Tach Generator (ur motor tach feedback).

Yes, 3 axes of drives likely a bit over 1k cost. Call the guys at MachMotion.com to get a quote - they have some really low cost drives (and motors) available with correct interface.