Biomedical Engineering Reference
In-Depth Information
Figure 2.5
Representative injection molding system for PEEK. Picture supplied with kind permission of Krauss Maffei
Technologies.
Consequently, the cost of the designing and fabri-
cating mold itself represents a significant financial
investment for this process. However, after this
investment has been made, multiple PEEK parts can
be manufactured in their near-final shape with cycle
times of the order of minutes.
Figure 2.6
shows a tree
of tensile test specimens immediately after injection
molding. The cylindrical sprue, radial runners, and
any extra flashing are trimmed to complete the part
manufacturing process. Because of the up-front cost
of a suitable mold, injection molding techniques are
not suitable for prototyping or low-volume PEEK
part production.
Most standard reciprocating screw injection
molding machines are capable of molding natural IG
PEEK materials and also carbon fiber-reinforced
PEEK materials (
Fig. 2.5
). Furthermore, specialized
injection molders with extensive experience in
manufacturing PEEK-based medical devices exist in
Europe and the United States. Injection molding of
PEEK typically requires barrel and nozzle temper-
atures in the region of 400
C. The recommended
mold surface temperature for PEEK lies in the range
of 175
e
205
C, and this is extremely important to
ensure that molded parts demonstrate uniform levels
of crystallinity. Failure to achieve the minimum
Figure 2.6
Injection-molded test specimens, joined by
sprue and runners. Injection molding allows multiple
PEEK components to be fabricated in near-final shape.
High up-front tooling costs are the main drawback of
injection molding. Photo courtesy of David Jaekel,
Drexel University.