Re: setting up the CNC mill

Boris,
In your software you can change the direction of the STEP pulse.
I don't mean the direction of motor, instead the signal from Pos to
Neg or Neg to Pos. Lets say the STEP signal sits high (POS) then it
pulses low (NEG) for each step. With an opto in the line the signal
is upside down. During certain turns, steps get lost. If you are
inverting with an OPTO go into your software and reverse the
direction of the step signal. CNCPro has it and so do others.

Bob

--- In CAD_CAM_EDM_DRO@y..., Boris Mara¾ <boris.maraz@p...> wrote:
> My controller uses the opto-isolators too. And they are the problem
as you
> say in your case.
> I tested the same G code program with demo version of DesKNC for
DOS and the
> program and the machine work OK.
> But when I use TurboCNC the error is here again. I don't blame
program but
> the opto-isolators or something with that.
>
> In my case the problem is not in loosing step or steps.
> Don't know how to explain but something like that is happening in
my mill.
> In each reversal from - to + (or + to - depends how is defined +
direction
> LOW or HIGH state) the first step in + direction is in - direction
and all
> other are correct in + direction.
>
> For example 6 step in - and 6 step in +:
>
> go-; go-; go-; go-; go-; go-; go+(but it still goes -); go+; go+;
go; go+;
> go+;
>
> correct
> | > > > > > > |
> | < < < < < < |
>
> wrong, what happening in my mill
> | > > > > > > |
> | < < < < < > |
>
> Maybe the problem goes away if direction bit is send in one
programming line
> earlier then step bit.
> But the problem will go away if I put away opto-isolators and I'll
do that
> just right now.
> And I will still use the TurboCNC. It's really good.
>
> Boris
>
> > Boris:
> >
> > Do you mean that if you execute G01 X-1 and G01 X+1 once it
returns to
> > almost 1.000 but is off by some small delta, but if you repeat
this many
> > times it drifts away from 1.000 a little more with each
execution? If it
> > doesn't return to the same point after each loop it's more than a
> > backlash problem.
> >
> > If this is the case it may be losing a step with each reversal +
to - or
> > - to +. Jon Elson identified a similar lost step in my machine. I
was
> > using EMC with an opto-isolator which inverted the signal.
> >
> > You might run this loop many times, say 100, and measure the
error in
> > returning to zero. If this is 100 times a single step (mine
is .00025")
> > you're probably losing one step each loop. If double it could be
two
> > steps, etc.
> >
> > I had the same error in both X and Y and it was consistently one
step
> > for each reversal in one direction. I tried a different
controller and
> > the error went away. I then took out the opto-isolator and the
error
> > went away with EMC. It was probably some wierd timing problem in
EMC but
> > once I got it working I didn't try to isolate the problem further.
> >
> > If this seems to match your problem try this. If not, never
mind. :-)
> >
> > Hugh Currin
> > Klamath Falls, OR