By Jeff Churill
Project:
Reverse engineer a tug hull, scale up to make a fiberglass mold.
Idea is to take an existing hull or hand made hull and build a
3D Computer Aided Design(CAD) model from Laser Scanning data.
I’ve been working with Laser Design for
about 9 months now and I have to say it was a good move for me.
Laser scanning is nothing new, our company has been developing
laser scanning probes for 20 years. It’s been the last few years
where things have really started to come together. The accuracy,
ease of operation and computer speeds make for one slick piece
of technology.
The technology is based on simple
trigonometry. The laser beam is projected onto the surface where
a set of cameras pick up the reflection. The
stereoscopic cameras are set at a known angle which then
“trigs” out the location of the beam over a given width and
distance.
These
laser Probes are placed on a Coordinate Measuring Machine(CMM)
or a hand held Portable Coordinate Measuring Machine which is
known as a FARO arm. Depending on the Laser probe, the field of
view ranges from under one inch to nearly a foot, the narrower
the field of view the more accurate the probe. Accuracy ranges
by probe type from .0005 to .005.
The Laser sweeps the hull gathering
thousands of points every second. A path plan is built so every
part of the hull can be scanned. The laser can only read “line
of sight” so the table will rotate to reach areas in different
views. The Probe head can also rotate to reach even hard to see
areas. The stereoscopic cameras allow one camera to pick up the
reflection where it may be blocked for the other. This scan only
took 5 minutes!
The scan “Point Cloud” looks to be a solid
CAD model, but it’s actually millions of individual points.
Here is an example of the point cloud
zoomed in. You can see the individual points. Each point has an
X, Y, Z, location as well as their I, J, K, vector or direction.
The point cloud is then pulled into a
software package from Geomagic. Here you can work with the
points in many different ways. For this project, a Polygon model
is made by connecting all the points with triangles known as
polygons. From here the poly model can be modified (Scaled),
then used for a CNC milling machine for molds or plugs.
The next step would be to surface the
Polygon model, creating a “solid CAD model”. Some CNC milling
machine software would require this in order to be milled. The
main purpose however for a solid CAD model would be to have a
true 3D representation of the hull, which can be pulled into any
CAD software.
We’ve had some very interesting laser
scanning jobs, from the John Force Funny Car “Frame” to the
Gulfstream new supersonic jet “Turbo Shaft Engine” to showers
stalls and even a Belgian Waffle iron. On the model end of
things we’ve done a G.I. Joe figure, a 1/24 Mustang, a clay
Concept Car and Burger Boats Yacht just to name a few. Which
I’ve really enjoyed working on.
http://www.laserdesign.com
Laser Design,
Inc.
45333 Five Mile Rd
Plymouth, MI
48170 USA
Tel:
952-884-9648
Fax: 952-884-9653
