R_Bibb_Medical_Modelling_The_Application_of_Adv.pdf

5.24 LOM TM model of the mandible.
Physical reproduction 93
is also the cost advantage of standard (photocopier) components and the
elimination of lasers. The more recent system offered by 3D Systems and
Israeli company, Solidimension Ltd (Sharga Katz Bldg, Be’erot Itzhak
60905, Israel) is aimed at the desktop concept modelling market. The
machine uses PVC sheet material supplied on a roll that is precision cut
with a blade and bonded with an adhesive.
The sheet materials these processes use undergo no state change and
therefore shrinkage is not a problem, although the height may alter slightly
as built in stresses are relieved. Paper models produced are good for
handling and feel similar to wood. The models will burn out of investment
casting shells with no problems. These models are very strong in compression
and may, therefore, be used as moulds for vacuum forming or light
duty pressing.
An inherent problem when breaking models out is that any area of the
model that faces upwards or downwards is attached to the waste material.
In practice, this is only a problem where the distance between laser cuts is
more than around 10 mm. This is partly combated by fi ner cross-hatching