Computer-Aided Manufacturing (CAM) of Biodevices - Advanced Design and Manufacturing Technologies for Biomedical Devices - page 165

9.3 Simulating Machining Processes

Preparing automated subtractive machining processes has been the traditional core
of computer-aided manufacturing. In this section we provide a case study linked to
the real development of a personalized hip prosthesis, including design personaliza-
tion, with input from medical images, and CNC machining for fi nal prototype
manufacture.
The example has been provided by Prof. Dr. Carlos Ojeda, current leader of the
Bioengineering Research Group at the University of Piura, Peru, and we would like
to thank his contribution.
Figure 9.1 shows schematically the personalized design of a femoral prosthesis,
adapted to the femur of the patient. The usual procedure for carrying out a custom-
ized examination with a view to using a prosthetic device usually begins by taking
either a computerized tomography (CT) or a nuclear magnetic resonance (MRI/
NMRI) of the patient needing the prosthesis.
Then, with the aid of .dicom or .dcm (Digital Communications in Medicine)
format, the information from the CT or MRI can be transferred to a program such
as “Mimics,” so that it can be displayed in 3D. These programs usually include
modules that allow selecting part of the patient

s bone geometry and storing it in .stl
or .igs formats that can be read by other CAD programs, for ad hoc design opera-
tions, after processing the images “slice by slice.”
Additional information, linked to a similar reconstruction and personalized
design, can be found in Chap. 5 (Ojeda Díaz et al. 2009 ).
Once the CAD solid model of desired prosthesis is obtained, the CAM resources
of the CAD-CAE-CAM software allow for manufacture preparation and simulation,
including the possibility of precisely defi ning tool velocity, precision required, and
tool change operations, among other aspects, linked to the roughing, semifi nishing,
fi nishing, and contour milling processes involved. Figure 9.2 shows different images
describing the whole automated CNC machining process of the personalized pros-
thesis, using different tools and advance and spindle speeds for the different
processes.
Figure 9.3 shows the “MAHO MH 600 C” CNC universal milling machine,
which was used for the prosthesis manufacture, as well as the beginning of the
roughing process starting from a block of raw material. Figure 9.4 details how
the roughing process continues and provides an image of the femoral component of
the fi nal artifi cial hip prosthesis obtained.
After manufacture some fi nal post-processes can be applied, including physical
and chemical vapor deposition (PVD and CVD) processes for improving several
mechanical and tribological properties, as well as corrosion resistance and fi nal
biocompatibility, as Chap. 13 details (please see Figs. 13.1 - 13.3 for some additional
examples).

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