R_Bibb_Medical_Modelling_The_Application_of_Adv.pdf

Table 5.5 Advantages and disadvantages of SLM TM and DMLS ®
Advantages Disadvantages
Physical reproduction 87
Very strong, very tough metal parts Relatively new technology
Accurate Very high cost of machine and materials
Materials can be sterilised easily Inert gas supply required
(using autoclave)
Wide range of metal materials
the powder. The advantages and disvantages of SLM TM and DMLS ® are
summarised in Table 5.5.
5.6 Three-dimensional printing
5.6.1 Principle
Powder material is deposited layer by layer and selectively bonded with
adhesive printed onto the powder by heads, similar to those used in inkjet
printers.
5.6.2 Detail
This process was originally developed at Massachusetts Institute of
Technology and commercialised by the USA-based company Z-Corp. The
machines use simple, relatively cheap powder materials such as starch and
plaster, which is selectively bound by printing an adhesive. The models have
to be removed from the unused powder, which supports the build as it
progresses. At this point, the models tend to be delicate and soft and
require infi ltration of a hardener material such as polyurethane or cyanoacrylate
resin. The machines are comparatively inexpensive and the material
and running costs are reasonable. The fi nished models are not as
accurate and the surface fi nish not as good as SL for example, but the
advantage is that the machine builds extremely fast compared to other
processes. This, combined with low running costs, makes the models comparatively
cheap. The fi nished models remain relatively weak compared to
FDM TM or LS models. The machines and materials are safe if slightly
messy.
The materials tend to be highly porous and, therefore, not well suited to
sterilisation, and no medical grade materials are available. The models are
opaque which may hide internal details. A typical Z-Corp medical model
is shown in Fig. 5.21. However, machines are available that can produce
full colour models. This is achieved by introducing coloured inks into the