10-11-2012, 04:14 PM
Rapid prototyping techniques for individualized medical prosthesis
manufacturing
medical_incremental.pdf (Size: 5.77 MB / Downloads: 70)
Abstract
Incremental Sheet Forming (ISF) process consists in the local deformation of a metal blank enabling a flexible
production of complex parts. It uses a punch moved by a CNC machine and it is suitable when customized
parts or small batch productions, short realization time and low cost are required. Moreover, since forming
forces are low, the geometrical accuracy of formed parts can be improved using full or partial dies. Those can
be made of resin, wood or realized by rapid prototyping techniques (RP). RP techniques realize parts adding
the material layer by layer. It can be a photocurable resin in form of liquid, a polymeric or metallic powder, a
wire or a solid sheet as a raw material. Products, such as medical prosthesis characterized by high customization
represent an interesting market for ISF. In this work, ISF Titanium and PCL prostheses were manufactured,
compared and discussed in order to study and optimize a reverse engineering and recreation process for
human body anatomy.
INTRODUCTION
Incremental Sheet Forming is a suitable process
when customized parts or small batch production
quantities are required in a very short realization
time and at a low cost. The process basic concept is
based on the forming of a blank: a hemispherical
tool locally deforms a metal sheet following a predefined
path (Jeswiet 2001).
Today there are many processes based on the local
deformation of metal sheet enabling the flexible
production of complex parts, but the incremental
forming process is attractive also because it can be
easily accomplished by a three axis CNC milling
centre (Jeswiet et al. 2005).
There are two kinds of incremental sheet forming
(ISF): Single Point Incremental Forming (SPIF) with
free sheet deformation and Two Point Incremental
Forming (TPIF) where a die is present under the
sheet. In this case, the presence of the die improves
the part dimensional and geometrical accuracy. To
reduce the tooling cost, the die can be made of resin,
wood, low carbon steel or by Rapid Prototyping
Medical image processing and 3D
geometrical model
Image processing is a noninvasive method to acquire
internal information about a patient. This technique
was first discovered by Roentgen more than a century
ago with the use of planar X-ray. Since then
much more advanced techniques have been developed.
Today, three-dimensional techniques such as
Computerized Tomography (CT) and Magnetic Resonance
Imaging (MRI) are of common use for diagnoses,
surgical planning and interventions. Basically
an anatomical image is obtained of internal
structures in form of a bi-dimensional (2D) dataset
of images and exported commonly in DICOM (Digital
Imaging and Communication in Medicine) an international
Standard (ISO). The 2D dataset is processed
by means of specialized software to separate
the region and structures of interest and reconstruct
the anatomy in a 3D model. (Fig. 1)
CONCLUSION AND FUTURE DEVELOPMENT
In this work, it is proposed the use of anatomical
digital image processing, rapid prototyping and ISF
techniques to reverse engineering and manufacturing
a plate prosthesis. In order to realize a personalized
part, reverse engineering process has been applied to
a human palate and titanium and PCL prostheses
were manufactured. Results showed the consistency
of the process, and, moreover, that in PCL Incremental
Sheet Forming it is possible to improve the
accuracy acting on the process parameters (low tool
feed, high spindle speed). A possible explanation is
given by the local heating of the sheet due to friction
action.
Ti showed a better accuracy but severe surface finishing
problems have to be solved.
In the future, the process will be optimized and analyzed,
also under the biological and clinical point of
view.