Rapid Prototyping, Rapid Tooling
Introduction, 01.03.2001
The laboratory is engaged in three main areas:
- Rapid Prototyping
- Rapid Tooling
- Laserscanning
An Introduction to each one of these technologies was given.
Rapid Prototyping
The machine consists of a tub containing the epoxy-resin, a
platform, a laser with a set of mirrors to control the movement of
the laser, and a computer with the software. The accuracy is 0.1
mm. On common CAD programms a 3D model of the desired object must be
created. STL files of this model can be used by the rapid
prototyping mashine. Most CAD systems have such STL interfaces. The
software now is slicing the model: dividing it into layers of a
certain thickness. The platform is lowered 0.1 mm underneath the
surface of the epoxy resin, and the laser is forming the first layer
of the object. The resin is photosensitve and curing when hit by the
laserbeam. So layer after layer is built up. When the whole objct is
done, the part is removed from the tub, excessive resin removed, and
placed into an oven and cured with ultraviolet light.
Rapid Tooling
Rapid tooling is dealing with the 'rapid' devolopment of tools that
are used to produce a small series of parts (10-10000).
Three different methods of rapid tooling are used:
silicon mold
First one part is created with rapid prototyping. Then silicon is
poured around this part and cured. The cured silicon cube is cut
apart, the part removed. Now the silcon can be used as a casting, in
vacuum-casting for example. Only few parts can be produced this way
(10 - 20).
spray metal tooling
A gun, fed with a wire, is melting this wire and spraying it on
the first part. This metal shell then is supported by a compound of
epoxy with aluminium particles, making a rigid cast. This casting
can be used for many parts (10000).
EP 250
This method is similar to the first one, only instead of silicone
an epoxy is used: EP 250. This epoxy feels and looks like metal, and
many parts can be produced.
Laserscanning
Laserscanning is used to create a 3D model from an existing
object. There are two types of laserscanning:
- scanning with three degrees of freedom. This can either be
translational scanning or rotational scanning.
- scanning with random degrees of freedom, which is a combination
of translational and rotational scanning. This method achives the
best accuracy and is used at the local laboratory. Nevertheless, the
accuracy is still only 0.2 mm.
First the object to be scanned is coated with a special material,
which enhances the brightness and reduces reflection.
Then the object is fixed on a platform. This platform can
rotate. Now the laser sends a beam, and two sensors are searching
for bright spots at an angle of 30 degrees (from each
direction). When a spot is found, then the distance from the object
to the laser source can be calculated by the angle (=30 degrees) and
the distance from the laser source and the sensor (which is known).