Computer-Aided Manufacturing (CAM) of Biodevices - Advanced Design and Manufacturing Technologies for Biomedical Devices - page 170

• Their low densities provide lighter fi nal implantable devices, what is also advis-
able if mechanical requirements are not too high.
Of course there are also some disadvantages linked to the extensive use of these
polymeric materials, such as:
• Their properties are infl uenced by temperature changes and mechanical stresses,
what complicates the design process and requires exhaustive characterization.
• Adequate experience is needed for promoting designs oriented to the fi nal manu-
facturing process, typically injection molding.
• Many polymers are toxic or environmentally harmful, as they are oil-derived
materials.
However, some of these diffi culties can be tackled by engaging good designers
in the development process, by using complete databases with detailed properties
( www.campusplastics.com ) , and by devoting researchers to the synthesis of new
formulations with biological origin, instead as based on oil chemistry.
In addition, other relevant related diffi culties can be solved by the use of ad hoc
developed computer-based design, engineering, and manufacturing tools. Linked to
the topics of this chapter, it is important to mention the extended use, in the polymer
industry, of computer-aided manufacturing resources for helping part and mold
designers to obtain more adequate designs.
Most renowned software for in silico assessment of injection-molding processes
is Moldfl ow (currently Autodesk Moldfl ow, which is also included within the
Autodesk Suite for product design, directly connected with Autodesk Inventor).
Details can be found in the website: http://usa.autodesk.com/moldfl ow .
Moldfl ow provides tools to help designers validate plastic part, mold, and tool
designs before manufacturing begins. Using a digital prototype to simulate the plas-
tic injection-molding process helps to reduce the number of physical (rapid) proto-
types required to optimize a plastic design and get the products into market faster.
Such software helps with material and injection machine selection, provides
information linked to injection cycle time, gives an idea of fi nal part quality, and
helps to improve the design and optimize production by changing the injection
points, by using multicavity approaches, and by changing materials and machine
parameters, among other possibilities. Related teaching applications are also very
remarkable in the fi eld of product design (Díaz Lantada et al. 2007 ; Lorenzo Yustos
et al. 2010 ).
Figure 9.5 shows the computer-aided design and the rapid prototypes obtained
by additive manufacturing (see Chap. 10 ) of a “gerotor”-type internal gear pump,
development carried out in 2005 to provide a teaching example of complete product
development process, oriented to polymers, for the subject “Design and manufac-
turing with polymers” (Díaz Lantada 2005 ). The prototype serves to validate the
assembly process, as well as to carry out some validation trials.
In order to fi nally adapt the design for promoting injection molding and pre-
designing mold structure, Fig. 9.6 shows some simulation results linked to the