R_Bibb_Medical_Modelling_The_Application_of_Adv.pdf

94 Medical modelling
over up-facing areas. It can also be avoided by re-orienting the model.
However, this is still a problem over large fl at areas or shallow slopes and
care must be taken when breaking out the model.
In medical modelling terms, these processes have some uses. They show
reasonable accuracy and surface fi nish. However, the major advantage is
the low cost of building very large solid models. This makes the process
ideal for producing models of large bones or soft tissues. These advantages
can be clearly seen in the examples illustrated in Figs 5.25 and 5.26. The
fact that unused material is solid means that it cannot be removed from
internal spaces and voids. The advantages and disadvantages of LOM TM are
summarised in Table 5.8.
5.9 Computer Numerical Controlled (CNC) machining
Unlike RP techniques, milling has always been of limited use when producing
shapes with undercuts, re-entrant features and internal voids. For
example, Section 6.2 Implementation case study 2 shows an image of a
5.25 LOM TM model of illium.