R_Bibb_Medical_Modelling_The_Application_of_Adv.pdf

Case studies 273
patterns were built in less than three hours. The results can be seen in Fig.
6.113, with the shallowest relief (0.1 mm) on the left ranging to the deepest
relief (0.8 mm) on the right.
6.17.7 Results
All of the texture depths were visible on the ThermoJet ® patterns. This
indicated that the process was capable of producing patterns with suffi cient
detail to describe realistic skin textures. The layer stepping effect commonly
exhibited by layer manufacture RP processes was not visible on the
surface and did not interfere with the texture pattern. However, textures
would not be well defi ned on down-facing surfaces due to the dense support
structure that, when removed, left a rough fi nish. This may be a problem if
the technique was used in the production of complex prosthetic forms
where all surfaces are on show such as hands.
6.17.8 Discussion
The tools available in FreeForm ® were well adapted to creating accurate
texture relief from two-dimensional images. One possible limitation is fi le
size. In order to represent texture faithfully and wrinkle detail at each stage
of both methods, large amounts of data are required. A high-resolution
model setting that demands a lot of computer processing power must be
used in the CAD stage. The output STL (Standard Triangulation Language)
fi le required for the subsequent ThermoJet ® production stage must also
have good detail defi nition that translates to a large fi le size. Whilst more
modern, high-specifi cation computers may be able to handle the large fi le
sizes, it may make the process unmanageably slow for others. Further
research will be undertaken in order to optimise the fi le size versus quality
settings.
The ThermoJet ® process was capable of producing all of the texture
samples faithfully and did not exhibit the stair stepping effect that some
other RP processes display. This ability, combined with the suitable
6.113 The six ThermoJet ® produced skin texture sample patterns.