Re: Brushed Servo & Motor Direction

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:

> Patrick wrote:
>
> >Group,
> >
> >I'm working on a benchtop cnc machine (pro light 2k) that uses brushed
> >servo motors for the axes. The problem is that when I command the
> >homing routine, the machine travels in the negative Y until it trips
> >the limit switch, and I get a "positional error." Z homes correctly,
> >I don't know about X because the routine errors on Y, and X follows Y.
> >Could the problem be as simple as switching the power wires on the Y
> >axis motor? I've done some searching of the software, and there does
> >not appear to be a user adjustable parameter for homing direction.
> >
> >
> No, it gets a lot more complicated. If you just swap motor wires, it
> will go crazy as soon as you turn on the servos. You'd need to swap
> the A and B wires in the encoder, too. That will completely reverse
> the axis, which I expect will get the sign of the motion reversed, too.
> In other words, when you command a +Y move you will now get movement
> in the -Y direction. If you manually move the machine to a place where
> the home switch is in the -Y direction, then when moving in -Y it

will hit

> the home switch first, before the limit switch. This may require moving
> the home switch to a different position.
>
> Jon

The home switch may be shorten.