3D technology of solids
production by means of laser's step-by-step propagation in the third
(volumetric)
direction can be used for nontrivial masses distribution of the whole
object. The background idea of such technology is in creation of
internal - totally closed hollows. Their dislocations, geometry and
orientations might be arbitrary.
Being
involved in CATIA V5 engineering software study and the following 3D
print I'd like to demonstrate here my vision, perspectives and
benefits of the approach of mass distribution formation by creation
of internal hollows in process of solids level-by-level growth.
Example: The Rattlebacks
(Celts) 3D printing
The Rattleback or Celt is
a semi ellipsoid, which axis of mass symmetry does not coincide with
geometrical symmetry. By means of it the solid possesses the
following mechanical feature: it turns simply in one direction
(direction of 'lighter part') and does not in opposite. Well, being
turned in 'wrong way' it stops, oscillates
and finally turns into another. There are many excellent references
in the internet showing detailed explanation and physics of this
phenomenon. It is very well known in theoretical mechanics during
centuries. To get the described non-symmetry one normally adds two
masses in the Celt's plane whose joining line has a small, usually
10-15 degrees deviation from the ellipse large axle. Or the same
effect can be obtained by small tilt of the plane relative to
vertical axis of rotation. Being students, we played with the last
one in practice of the theoretical mechanics course in the Moscow
state University.
Nowadays 3D printing
technology brings into the world of Rattlebacks one new amazing
thing: for an external observer the Celt canbe totally symmetric. The
described above ways of the mass non-symmetric distribution are
relatively easy to detect. It is very well seen externally and
usually unprepared person explains the Celt's behavior by it's
non-symmetry. But how the same person will explain the physics of
externally totally symmetric Celt?
Here are my CATIA's figures
of internal hollow spheres distribution and production technology
(not shown). The software makes preliminary calculations of the
center of mass position, moments and principal axes of inertia.
