Re: Re: How does G02 & G03 work?

Ray Henry wrote:

> From: Ray Henry <rehenry@...>
>
>
> Jon, Darrell, and other nc writers
>
> I confess to being a bit confused by the lines of nc code offered in
> the
> posts below and have mixed my comments in.
>
> My understanding is that i,j,k, and r are incremental when they are
> used
> with g02, g03 and are figured from the current tool position at the
> start
> of the block in which they are included.

Yes, this is all correct, for IJK. R is not really incremental, it is
just the circle's radius.

> Fagor (the only book I've got
> handy) uses g06 if you want to enter absolute values for i,j,k, or r.
>
> I've dropped a graphic from my backplotter of both of the desired tool
>
> paths you speak of in
>
> http://www.linuxcnc.org/Dropbox/g02ij.gif

Now, the way EMC works seems to have changed, since I went through the
IJK
modes of the arcs about a year ago. At that time, I was sending only
positive
IJKvalues, as with my old Allen-Bradley control, and it seemed to work
fine
except for the starting and ending radius problem. That forced me to
change
to R for radius, which is a lot less ambiguous, anyway. But, using the
R word
just gets rid of this problem entirely, because you specify the radius
directly.

On your drawing (which looks GREAT, by the way) you have a dotted arrow
which is labeled this is +I, which goes from the END of the arc to the
arc
center. That is a bit confusing. Yes, I know, it is hard to draw a
zero-length
arrow.

Jon