Re: [CAD_CAM_EDM_DRO] Re: setting up the CNC mill

If your High-Low signal needs to be reversed, be sure to see Doug Fortunes
12:42Pm Post for a fix using a NAND Gate ! I had the same issue with MicroK
drives and Indexer LPT. Ran excellent, but it would lose a very calculable
amount of steps. Direction signal was not correct for the driver. Indexer sent
Low I think....... MK drives wanted high...............

Chris L

Boris Mara¾ 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
>
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