Re: Can You Machine NURBS?

Hi Alan,

I found this link for you. Take a look.

http://www.mmsonline.com/articles/hsmdm/cnc5.html#


Matthew




--- In CAD_CAM_EDM_DRO@yahoogroups.com, Alan Marconett KM6VV
<KM6VV@a...> wrote:

> Hi Matthew,
>
> While I've heard of NURBS, I hadn't heard of "NURBS G-code". What

are

> the specialized Gcodes involved? do you have a sample and/or a
> reference? I'd thought it might be neat to do an "ellipse Gcode",

but

> then I don't cut many ellipses (or parabolas!)!
>
> Alan KM6VV
>
>
> "mjf462001 " wrote:
> >
> > NURBS stands for Non Uniform Rational B-Splines. It is a way of
> > discribing a complex curve by math equations. Simular to splines.
> >
> > If you have ever milled complex flowing curves (not a true arc)

and

> > tried to do it with precision you notice that the post files can

get

> > very large. The reason for this is that most cnc controllers can

only

> > interpret straight lines and arcs/circles.
> >
> > The really neat free flowing curve that you drew in your cad/cam

has

> > to be broken up into really small lines or arcs to approximate the
> > original curve. So besides the really large post file you still

are

> > not going to be able to machine the exact shape you drew. But you

can

> > get close.
> >
> > NURBS interpreters (CAD/CAM) will allow you to draw those

artistics

> > shapes and import the math equation directly into the machine
> > controller. It is then up to the controller to calculate the

cutter

> > path. It only takes a handful of lines of NURBS G-Code to

describe a

> > complex free flowing curve. There are two advantages to this, you

are

> > able to machine the exact shape you drew, and the post files come

out

> > of the CAD/ CAM with a 60-90% reduction in size.
> >
> > If you have ever milled a curve consisting of lots of small

segments

> > you know how taxing it can be on your machine. The surface finish
> > also suffers from these small jerky movements.
> >
> > Hope that helps
> >
> > Matthew