3D machining

Ian Wright wrote:

> Can someone who is familiar with 3D machining on a cnc machine please tell
> me what form the DXF file should take. I need to draw up some parts for a
> project which I hope to be able to make on my little mill when it gets
> finished but I can't decide whether I need to draw them as Autocad 'Solids'
> or as 'extruded planes'.

I'd model it as as a solid, then export it as a 'sufficiently high' resolution
STL (Surface Triangulated Language - or - STereo Lithography ) because
several affordable (I'm not going to say 'low end') packages can take that
format. In particular, Millwizard ($250), Deskproto ($1500), Fred Smiths
STLWork ($ ?).

The problem with STL is that you still have tiny triangular planes, so for
really precise work, you need to export IGES (or other hi-end format),
which treats the curves as curves, rather than short straight lines.
The problem is that only really expensive packages can convert these
formats to gcodes, so you are stuck with STL if you are on a budget.

On the bright side, STL is amazing good. Just bite the bullet and
go get 128->512 MB of ram memory - don't try it on 32 MB !

Doug Fortune
http://www.cncKITS.com