Re: [CAD_CAM_EDM_DRO] Geometry Problem

Ron Ginger wrote:

> From: Ron Ginger <ginger@...>
>
> I am trying to add another feature to my CNC program, and am stumped
> on
> a geometry problem, maybe someone here has an answer.
>
> I want to handle the transition between 2 line segments. Assume I have
>
> points X1,Y1 as the start of a line, X2,Y2 as the end of the first
> line
> and start point of the second, and X3,Y3 as the end of the second
> segment. I also know to mill either to RIGHT of the line or LEFT.
>
> If I am on the outside of a corner, I want to do and arc, with the
> center at X2,Y2 and start and end point determined by the tool offset.
> I
> know how to do all this.
>
> If I am on the inside of the corner I need to find the intersection
> of
> the two tool paths and stop at that point. I know how to do this as
> well.
>
> What I cannot figure out is how to tell which case I have. So, given
> the
> 3 points and an offset of right or left, how do I tell which kind of
> corner I have?

The CNC program has no way of knowing which side of a line the material
is on,
unless you TELL it! That is what the G41 and G42 commands are for.
But, it gets pretty tricky with inside corners. You can't make an
inside radius
smaller than the tool radius, and even making a radius equal to tool
radius may
cause gouging or chatter marks in many cases.

OK, if you are assuming you DO know right or left, then you have to
decide whether
the 2nd line goes right or left. Assuming the offset is left, and the
first move is a
+Y move, for instance, and the 2nd line goes +X, that would be an
outside corner.
A -X move would be an inside corner.

Jon