Re: [CAD_CAM_EDM_DRO] NURBS fer nerds..

Brian,

> So ah,, what does a NURB do for me?? I usually draw stuff with VISIO
> and Cadkey. The solids stuff just seems lots easier for hackers like
> myself.

Tim's reply gave a short answer, here's a long one FWIW... :)

Most 'solids' are a set of NURBS bounded surfaces... So when the solid
modeller can't get you the effect desired, you can get it by constructing
the NURBS surfaces yourself. It might be more appropriate to say that
NURBS-based surfaces are the more visible aspect of what a NURBS does for
you.
Some examples of what you'd use NURBS for on the modelling side would
be: free-form 'organic' type shapes, defining a specific surface shape to
join two solids or 'face' edges, odd fillets that won't construct
automatically, custom surfaces for mold splitting, capping holes/pockets
before CAM.
On large models it is useful to speed up the CAM toolpath generation by
'exploding' the solid model and exporting only the surfaces to be machined.
ie. Processor time isn't wasted rotating the 5 additional sides of a cube,
not to mention time spent with internal detail detection/relevance
checking/rejection, etc. Perhaps that isn't relevant in a home shop, but the
concept of reducing processor load is. Most people dislike the wait for
large toolpaths to be generated.
NURBS surfaces can be looked at as a much quicker way of defining your
machining area - selection of the surface areas to be machined, vs the
surfaces edges per area. (BobCAD, Vector non-NURBS) It can allow the 'facet'
or 'arc interpolation' settings within the CAM program to set the accuracy
of the generated toolpaths.
NURBS in CNC control would seem to be an ideal way of minimizing the
huge programs generated for molds, patterns, etc.; though I'm personally not
familiar with controls that use NURBS as toolpaths, or surfaces as direct
input.

Regards,

Keith