Re: [CAD_CAM_EDM_DRO] Re: 3D Contouring - Loss of Accuracy

Chris L wrote:

>
> Obviously, manually performing a "homing" event is not hard..... but,
> some machines and limit switches need to go slow as it hits them. And
> then, like in my case where I have the machine "Step Off" of the
> switches quite a ways for actual Machine Zero, well, this too can take a
> little time. I don't like standing around waiting for it to do that.

I suggested to DaveK (author of TurboCNC http://www.dakeng.com/turbo.htm )
that if a guy buys his A&B channel rotary encoders with the optional
index channel (from someone like http://www.usdigital.com ) then checking
and re-syncing could be done 'on-the-fly'.

ex: Chris is worried that homing to a position 6 feet away takes a lot
of time, not to mention the extra wear & tear.

However, checking the index mark (say on a 5 TPI leadscrew) can be done
every 0.2 inches on each axis, without loosing time, even on stepper
systems (which can ignore the A&B channels, but pay attention to the index
channel once per rev). When the index mark goes buy, just re-sync the
counter to the theoretical exact position again. (ie if you think you
are at 5.4012 and you see the index mark go by, you reset to 5.4000 which
can be done even though the axis is moving, or is moving rapidly).

Doug Fortune
http://www.cncKITS.com