Re: [CAD_CAM_EDM_DRO] Synchronizing Two Servo Motors

H & J Johnson wrote:

>Steve, I started out w/ steppers but changed "up" do to not having enough
>power out of the steppers. It still worked w/ Steppers, it's not to often that
>one will die and the other not... maybe lose some steps but a few steps
>doesn't bother my gantry. On the other hand my servos need to fault
>out [as you pointed out] before Mach stops. However this is a grand
>total of 0.025" rack.. again.. not really an issue.
>
>Driving two Step/dir drives off of one set of S/D pins is a no-no in that
>it's NOT absolute, there is no way of knowing where each drive is in
>relation to the other and whether each drive is seeing an equal number
>of steps, your much better off seperating the pulse trains via the control
>and slaving them, in the control.
>
>

I agree that using one set of pins per drive is best, but with some
simple buffering you can save those parallel port pins for something else :)

>As far as I'm concerned, Mach does it and it IS turnkey [select three radio
>buttons in the config settings].. I've been running my machine for more
>than 2 yrs this way.. and it works great.
>
>

It's a little easier to set up in Mach, but for that level of turnkey,
EMC2 also qualifies. The difference is that you have to add two lines
to a text file to connect the X (or Y) step/dir signals to a couple of
extra port pins. Actually, if you use stepconf to generate a stepper
config, you can just select as many pins as you like as "X Step" or "X
dir" - no slaving needed.

Since this arrangement doesn't have the controller deal with missed
steps or position errors, there isn't much you need to do to set it up.
- Steve