Re: DXF v's IGS file formats / advice needed

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "junebrandy" <mike1@j...>
wrote:

> Hi all,
> I am trying to develope G code for a section of a boat,, the
> original design is in Rhino, and the sections will be cut using a 4
> axis wire machine
> I started using DXF file format but got a million pointsand lots of
> confusion on my part.
> I then switched to IGES or IGS and now have a nice easy to follow
> section ,

As answered on the Vector user forum:

"Vector 9.6 will open a Rhino 3dm file directly. There is no
requirement to export to another format.

The DXF format does not support mathmatic surfaces. It can contain
curves and triangulated surfaces, similar to the surfaces in an .stl
file. At most resolutions, these are sufficient for machining.
However, you need to apply some common sense. Since sculpted surfaces
are usually for aesthetic purposes, they need to look nice, and not
necessarily be totally accurate to 6 decimal places. Never specify a
surface triangulation error/accuracy that is finer than you need. If
you need to make a surface that can be held in two hands, you can't
possibly receive a benefit from a resolution finer than .001, and if
it is for woodworking, probably .005 inches.

For parts less than 1/2 cubic inch, like a coin, jewelry or similar
small decorative objects, you might need to drop down to .0002. I
would not recommend anything smaller than 10-20% of your smallest
ball nose cutter radius.

Some DXF files contain ACIS solid bodies. These entities are not
available to cad programs that are not ACIS based solids modelers.
Rhino is not an ACIS solid modeler and will not have these entities
within it's DXF files.

If you need to create pockets, outlines, drilled holes and other
features that use 2 1/2 axis machining, use wireframe outlines, not
surfaces. These will have the same practical accuracy (more decimals
than you can count on one hand) in a DXf or iges file. "

Copied with permission from http://www.imsrv.com/discus

Fred Smith - IMService
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