Re: How to go from 2.5 D to real 3 D ??

Thanks Rab,

That's along the lines of what I was wondering. I'm not sure I need any
truly off axis arcs right now, but I can see that rotating arcs (as Doug
said?) could make it easy to cut something like a hemispherical shape.
The site is interesting, Don't know if I could afford the software!

Have you heard of any Gcodes to rotate a plane? Or how other planes
(besides G17,18,19) can be specified to a controller?

Alan KM6VV

rab@... wrote:

>
> All,
>
> Northwood Designs whose site I've just found, discuss this in their
> technical White Paper at:
> http://www.nwdesigns.com/Tech_paper.htm
>
> To quote:
> "Arcs may be fit in one of three methods: 1) relative to the standard
> orthogonal planes (XY,XZ,YZ). 2) relative to any rotation of the
> standard orthogonal plane. 3) to completely arbitrary planes (3D
> arcs). Almost all controls will machine arcs using the first method,
> some controls will allow method number 2, and a few controls are able
> to machined true 3D arcs. (*note- a 3D arc is not a helix)."
>
> They actually have a program that converts a file comprising of many
> short linear moves into arc movements or NURBS curves for controllers
> that have difficulty with high resolution files.
>
> Their site has a couple of demos and info on the subject, well worth
> a visit.
>
> Hope this helps,
> Rab
>
> > We do plenty of arcs in XY plane (G17), and perhaps some do arcs in
> XZ
> > or YZ (G18, G19) as well. As far as I've learned, arcs must be in
> one
> > of these planes, unless line segments are used to generate an arc.
> >
> > Are there controllers (and CAD programs) that can generate true
> arcs in
> > other then these defined planes? I can see how to draw an arc in
> CAD,
> > and then rotate it in an axis. I don't recall any Gcodes (NIST,
> RS274)
> > that hint at a way to revolve, or define a plane in either then the
> > mutually perpendicular planes. I have no idea "how they do it".
> >
> > So far, my CNC needs/interests have been met by "edged" surfaces. I
> > anxious to experiment with "water line" cutting, and smooth
> contours.
> >
> > Alan KM6VV