Biomedical Engineering Reference
In-Depth Information
Figure 2.9
PEEK polymer extruder. Photo kindly supplied by Coperion GmbH, Stuttgart.
two heated platens. The lower platen contains
a recess for the plate or sheet that is charged with
resin powder or granules. The platens are then
pressed together and heated to consolidate the resin.
Compression molding is typically used for low-
volume production, prototyping, and evaluation work
or in the production of industrial components with
very thick sections. Compared with injection
molding, it is a relatively inexpensive process, but
cycle times are long and as such it is not suited to
high-volume production.
The process involves the heating and cooling
down of the melt and tooling. Pressure is applied
to the melt and maintained during the cool-down
phase. This is a time-consuming process, particu-
larly when section thicknesses are large. Compres-
sion molding of PEEK requires a heated press, an
oven, and the tool, which can be low-grade steel/
metal due to the levels of stresses, shear, and forces
involved. There is generally a preference for fine
powder grade of PEEK polymer for compression
Figure 2.10
PEEK-OPTIMA rod stock, pellets, and
powder.
injection-molded components. This is highlighted
graphically in
Fig. 2.11
.
2.5.3 Compression Molding
Compression molding is a manufacturing process
for stock shapes, such as plates or thick sheets
(
Fig. 2.12
). A compression molding press consists of
