(Sorry to start yet another thread on much the same subject, but this
is a bit broader-ranging)

It seems that spindle-synchronised motion is very sensitive to encoder
regularity.

Using the p-port to read the encoder position means that as the
encoder linecount goes up, quantisation error in the measured
positions also goes up, and so the inter-line period noise increases.
Does this mean then, that very low linecounts will give less dither,
and better results?
http://www.pastebin.ca/1583502
Is the raw halscope data from my machine. If you plot the encoder
position it looks dead straight, but the raw data shows that the
difference between successive samples is quite variable.

Is this possibly the reason that my attempts at threading are so hopeless?

I would be the first to admit that my encoder is rubbish, it is a bit
of computer-printed paper wrapped round the lathe spindle, but even if
I was to get a high-accuracy encoder disc I feel I would still be at
the mercy of sample quantisation errors.

Any opinions on the best way forwards? I have got to the position
where I want to start the project that I started building the lathe
for, about a year ago. I don't really want to pull it all apart to
change to an FPGA board if that is avoidable.

-- 
atp

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