> From: andy pugh [mailto:[email protected]]
>
> On Wed, 20 Jan 2021 at 16:09, Kirk Wallace <[email protected]>
> wrote:
>
> > I left the trail here:
> > > https://github.com/LinuxCNC/linuxcnc/blob/master/src/emc/rs274ngc/interp_convert.cc#L4881-L5028
>
> There seems to have been a lot of time spent investigating theory that
> could have been settled in 5 minutes with an experiment.
>
> --
> atp
Dropping an apple from a tree and observing that it falls and smashes on the
ground doesn't splatter into the words that spell out laws of motion made up of
bits of peel and apple.
I'm assuming that the authors of this code were clever enough to take into
account the motor acceleration relative to spindle speed on each pass. But
that doesn't explain how they do that.
And if there are 60 teeth on the spindle encoder with a single sensor then 120
edges are the most you get. That's 3 degrees per edge assuming the slots are
symmetrical and I don't think there's a rule that they must be. Might be 1 and
5 degrees. So assume then an index single rising edge is used every 6 degrees.
A half inch shaft has a circumference of 0.3925" and each 6 degree index is
0.00654". The implication is depending on spindle speed and motor acceleration
you might be off by almost 0.006". That's a lot isn't it?
John
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