Look Ahead

[William Scalione <scalione-at-home.com>]

I am curious about the look ahead function in EMC. I was doing some engraving
in aluminum today that consisted of lots of  small squares. The cam program
made
the toolpath from zigzags. Anyway, at about 40ipm the corners of the zigzags
were
nice and square but at 100ipm the corners were noticeably rounded. Is this a
function
of the look ahead or is this something else? I also noticed that when I was
milling the
table (made from mdf not metal) to be true with the cutting tool, it would not
go all
the way to the end of the x axis if I had a high feedrate. see example code
below.

X0Y0
Z-.05
X20
Y.25
X0
Y.5
X20
Y.75
X0

At a low feedrate x would go all the way to 20 but at a high feedrate X would
only go
to 19.75

One last thing, not sure if this is really a bug or just part of the design.
When changing from
steppermod to freqmod it is necessary to change the direction of all three
axis' in
the INI file.


Bill