Re: Look Ahead

["Matt Shaver" <mshaver-at-erols.com>]

> From: William Scalione <scalione-at-home.com>
> I am curious about the look ahead function in EMC.

The look ahead feature ensures that there won't be a pause at the end of each
block while the control figures out how to execute the next block.

> 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?

You're using simple step & direction drivers, right? I mean these aren't the
pulse multiplier drives from Gecko are they. If you have the basic type of
S&D drive, I'd say this is a bug. There are a couple potential workarounds:

1. I think G06 puts the control in "exact stop" mode. I'm not sure if this
works, but you should give it a try.

2. See skeleton.txt for an example of how to use g04. What you can do is
something like:

G04P.001X0Y0
G04P.001Z-.05
G04P.001X20
G04P.001Y.25
G04P.001X0
G04P.001Y.5
G04P.001X20
G04P.001Y.75
G04P.001X0

> 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.

Small bug.

Let me know if either of these ideas works (or not...),
Matt