E_KM_AHEAD-Magazin_2-12.pdf - Netstal

20 Processes & Products
AHEAD Issue 02.2012
Processes & Products
EFFIcIENT MANUFAcTUrING oF
FIBEr coMpoSITE coMpoNENTS
KraussMaffei offers an entire range of processes to manufacture fiber composite components (also see the
cover story on page 5). The latest processes include different variants of resin injection processes. Here is a
brief overview of the latest developments.
New process variants expand the RTM (resin transfer molding)
technology application field Fiber-reinforced plastic parts are characterized
by extremely low weight but high rigidity. “Which manufacturing
process is best suited to a specific component depends on numerous
factors,” said Erich Fries, “above all, the component shape,
the matrix material, and the quantity required are all influencing factors.”
The performance profile and the production costs of the component
are also critical criteria. They determine which solution approaches
and manufacturing processes should be taken into account.
High-pressure resin transfer molding (HP-RTM) with quick reacting
resin systems The HP-RTM process (High-pressure resin transfer
molding) is suitable for large series manufacturing of lightweight
and high-strength structural components made of epoxy resins.
However, polyurethane or other reaction resins can also be used as
matrix materials. In HP-RTM, the resin is fed into the closed mold
using a self-cleaning high-pressure mixing head. The resin and hardener
components are injected into the mixing chamber via separate
nozzles and are mixed there quickly and intensely. This technique allows
fast-reacting resin systems to be processed within short reaction
times. Using high-pressure injection, the matrix resin wets the
fibers faster, more intensely, and more completely than by using the
low-pressure technique.
The mold can be evacuated and operated with an inner pressure of up
to approximately 100 bar. Even complex, three-dimensional cavities
are filled faster this way and the fibers inside are saturated. At the
same time, air voids are eliminated. There are constant new customer
requirements in the emerging lightweight construction and fiber
composite materials sector. KraussMaffei continuously develops its
process and machine technology for this dynamic environment.
Compression resin transfer molding (C-RTM) and wet molding
– two new HP-RTM variants In C-RTM, the mold is not completely
closed initially, but only up to the defined gap. Next, the resin mixture
enters the mold, with or without low mold-internal pressure. Some of
the fibers are already saturated by the resin; the greater part of the
resin quantity, however, is virtually “floating” on the fiber above. This
is followed by a compression stroke – the mold is completely closed
and the cavity corresponds to the shape of the final component. The
compression stroke has the effect of pushing the resin through the
fiber in the Z-direction and the fiber is wetted completely. This process
is advantageous for delicate preforms due to the low material
flows.
KraussMaffei is providing another alternative to the automated series
production of fiber-reinforced lightweight components in the form of
the wetmolding procedure. Here, a fiber pile is fixed in a flat state
without preforming. The mixing head is not positioned directly on the
mold, but is fixed on a traversing unit. While the mixing head moves
in a line over the fiber stack, the application device applies a laminar
thin resin layer on the fiber stack. As soon as the fibers are covered
with resin, the fiber pile is transported to a mold and pressed
there. The preforming of the fibers in wetmolding thus takes place
first with the mold closing movement. An important advantage of the
wet-molding process is that even recycled fibers can be used to reinforce
components. MB
c-rTM, coMprESSIoN rTM
10.
9.
8.
1. 2.
7.
1. Semi­finished products from
the roll
2. Handling the ready­made
semi­finished products
3. Transfer to the preform station
4. Preforming
5. Transfer the preform to the
CRTM station
6.
6. Close the mold on the compression
stroke, vacuum (optional)
7. Resin injection
8. Press (compression)
9. Hardening
10. Component removal
3.
5.
4.