On Wed, 2007-10-10 at 22:51 -0400, Stephen Wille Padnos wrote:
> Kirk Wallace wrote:
> 
> >[snip]
> >--- hnc-3a.ini ---
> >... snip
> >FERROR =                        0.0005
> >MIN_FERROR =                    0.010
> >... snip
> >---
> >  
> >
> Note that this gives you a FERROR of 0.010 at all speeds.
> 
> You'd want to swap those two values if the intent was to have small 
> allowable error at low speeds and higher allowable error at high speeds.
> 
> That calculation is done by setting the allowable error at top speed to 
> FERROR.  At lower speeds, allowable error is proportional to current 
> speed / top speed (so at 50% speed, the allowable error is 50% of 
> FERROR).  This is clipped at the low end to MIN_FERROR.  This is so very 
> slow motion doesn't end up with zero (or <1 encoder count) allowable 
> error due to roundoff.
> 
> - Steve

It makes sense that MIN_FERROR could be much smaller than FERROR, but
after making other adjustments and cut and try, I worked these numbers
down to FERROR = 0.0002 and MIN_FERROR = 0.0025. It may be an indication
that there are issues that I have yet to discover.

-- 
Kirk Wallace
(Hardinge HNC lathe, California, USA
http://www.wallacecompany.com/machine_shop/ )



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