point cloud to parasolid

[huhtis]

Hi,

I'm new in 3D scanning, new in 3D CAD, and I'm in problems

well my mission is to get a geometry of the horn (of the horn loudspeaker) to the Comsol multiphysics (that is a FEM modeling software) to study the acoustical parameters of a horn (for example acoustical impedance) and compare that to my measurements and simplified models.

I'm doing my thesis project at the Helsinki University of Technology and I've studied acoustics but not machinery or so..

I've have now point cloud measured with some big old and blue NC machine that had a touch probe attach to it. The probe didn't reach all points inside the horn and it didn't compensate the radius of the touch probe (r=3.9625mm).

I found a Rhino 4.0 from the computer classroom in our university that I tried first. I have now rhinoceros Wenatchee running on my own OS X (rhino for mac). I've tried to do the job with that but it's not done easy or I just don't how to do it.

What would be the best, cheapest and easiest way to do a surface, offset that surface in normal direction by the radius of the probe and then translate it to parasolid or step (that are recommended formats importing geometries in comsol)? Can I do this with rhino? What would be the command to look for?

You can get a view of my point cloud just plotted with a matlab from the .jpg-files in http://users.tkk.fi/~ihuhtaka/temp/horncloud/

Any suggestions?

-Ilkka

[Michael M]

http://www.emicroscribe.com/uploads/...mpensation.pdf

might be of help to you. I found that by googling on "digitizing probe compensation" and it was at the top of the list. I haven't looked farther down the links to see if there is anything else useful.

cheers,
Michael

[bostosh]

Get a point cloud - to - 3-D mesh software and create mesh.
OR
Use 5 "Z" point strings, convert to splines, then cut splines with planes to get planar strings of points. for (next)
Then cut with planes to get 4 or 5 point cubic or conic (planar) curves.
(Those are probably exponential curves)

Build a parametric, 3-d model, to offset probe dia. from.
Remember that the ball tip XYZ does not have a surface normal to define where the actual measurement is from. It is just "dumb" data.

Then with "real" analytic geometry you can manipulate, analyze or re-create the form.
Nice pictures and data set (.txt) way too many points, they make rough forms, better too many than too few.