Re: G-Code Arc drawing question

Dave,

G code is supposed to use "right hand rule" to determine/define
direction for G02/G03 arc commands...

Right hand rule states that you must "look" at the two ACTIVE axes
FROM the PLUS(or positive) direction of the UNINVOLVED axis to
determine CW or CCW.

So in G17 (arcs in XY plane, and the default for vertical mills) we
look from the plus Z to determine arc direction (above the spindle,
looking down for a vertical mill).

In G18 (arcs in XZ plane) we would look from the "plus" direction of
the Y axis.(vertical mill again assumed for the following) Since TOOL
movement is what defines plus and minus, a tool moving AWAY from us
is moving in the positive Y direction. (note: It may be the TABLE
moving TOWARD us, but the TOOL is still moving positive). So we would
need to get behind the mill to "see" proper CW and CCW.

In G19 (arcs in YZ plane), the uninvolved axis is X, so we need to
look from the plus side of X to see CW or CCW. Using our vertical
mill example, we would go around the right end of the table and look
back toward the mill spindle.

Hope this helps.

Ballendo

--- In CAD_CAM_EDM_DRO@y..., Dave Engvall <dengvall@e...> wrote:
>Slightly off topic but emc will use G18 (y-z) plane G2 or G3.
>However be careful of the sense...i.e....test on foam first as it
>doesn't seem to cut the way I would expect, seems to interchange G2
>and G3. Ray tried it on backkplot and agrees that is seems
>backwards at least to intuition.
>
>I've not tried G19 but expect it to work also....and also it may
>surprise you...test first as going the wrong way into a big chunk of
>steel can be a shock.
>
>Best Wishes,
>Dave