Re: 3D model

I have done quite a bunch of land models. I cut them on a 4'x8'x4'
table so just a bit bigger than what you are talking about. But its
all the same proccess.
I usually use 10 meter dems and tile them together to get the ruff
area I want then cut out the specfic area I want. Export the area I
want as a dxf. Make sure your vertical exageration is done in your GIS
software. You can do it later but I like to do it before. Save the
area out and in your cam program set the X or y size. Turn on
constraints and that will make sure it will scale correctly. The dxf
is a solid so you should not have to create points or surfaces. I
don't use Bobcad its to backwards and hard to usefor me. I use
Visualmill or Deskproto or Artcam to generate the toolpath. In those
you can set the bit you want and don't have to worrie about gouging
the work. Then you can go back with a smaller bit to get the areas
missed with the bigger bit. Also you can simulate rather accuratly
what it will look like with each bit.
If you just have a txt file with the xyz points you can use Accutrans
to make a solid. Works pretty good and is cheap.

Donny

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "ebiz_59" <chuckm@...> wrote:
>
> I've snooped in this group for a while, hoping some day to get a CNC
> unit. I've found a friend who has a Rong Fu 7x22 with BobCad 20, and
> a middle school student who has got a project that might work on the
> mill, but we are a little unsure how to proceed. The project is to
> make a 3D model of a transect of our valley. I am more a geographic
> information (GIS) guy and can provide either a set of contours lines
> or polygons, or a gridded surface, or probably even a set of 3D points.
> The question for the group is which is the best way to get this GIS
> information into BobCad? The GIS stuff is probably best represented
> in UTM (meters N of equator and meters E of a special meridian and
> meters above sea level). Should we then rescale this in BobCad, or
> before we get there? Does BobCad import Dxf, as I think I can export
> in that format? How do we ensure that the naturally sharp ravines etc
> are represented in a way that allows for tool dia, and won't preempt
> the project?
> I think we are looking at shrinking a 10 mile distance to the 20+ inch
> excursion of the mill, and exaggerating the Z axis to about a 2 inch
> excursion (it is maybe 1800 ft total in real life)
> Thanks for any help.
>