FOR AUTO RTM

PLANT TOUR
FIG. 5 Parts, parts ... and more parts
Visible throughout MCT’s Žebrák facility tour was evidence of highquality,
volume parts production.
TABLE 1
PREPREG
MCT COMPOSITE PROCESSES
Parts/yr Tooling
Pressure
(bar)
Variations
Autoclave 1 – 100 Al, CFRP 6 -
Miniautoclave
-
500 – 2,000 Steel, Al 4 – 12
NON-
PREPREG
Prepreg
Press
Wet
Pressing
1,000 – 5,000 Steel up to 30
10,000 –
100,000
Steel
up to
100
LP-RTM 1,000 – 5,000 Steel 10 – 40
HP-RTM 10,000 –
50,000
-
-
• Solid
• Cored
• Hollow
Steel 100 • Solid
The MonoCell’s six-piece automated tooling and molding
process is impressive (see Fig. 1, p. 54). The molding area is
surrounded by safety gates, and as the molding cycle begins,
warning lights and alarms demand that the area be cleared. Metal
floor grates open up and the side and rear tool sections slide in
to completely enclose a complex carbon fiber preform already
placed onto the fixed central tool section. The actuated tooling
allows the tub to be demolded even with an undercut. A single
injection point supplies epoxy resin, followed by a several-hour
cure cycle. After cure is complete, the tool sections slide apart
and a robotic arm with a vacuum/suction attachment picks up
the finished tub and eases it out of the mold. The robot then
places the MonoCell into a mechanized ceiling track (see Fig.
2, p. 54), which moves it through various finishing operations.
Meanwhile, another tub preform is placed onto the tool and the
molding cycle begins anew.
The front end of the 650S MonoCell features a large integrated
aluminum insert to which the front crash and bumper structures
will be attached. In fact, aluminum inserts have been embedded
throughout the monocoque preform. When cured, the part’s
digital design files serve also to guide location and precision CNC
machining of each aluminum hard point. Siegmann notes that
it is better to integrate inserts or hard points into the composite
structure vs. bonding on afterward. “Bonding is time-consuming
and adds risk to tolerances,” he explains. Integration, however,
demands very tight tolerances for all tools and machining jigs.
But for MCT, Siegmann points out, maintaining tight tolerances is
standard procedure.
Completed tubs ship twice each week to McLaren’s Woking,
UK, production center. More than 6,000 MonoCells have been
made to date, part of a contract secured in 2010 for 25,000 monocoques
over eight years for the MP4 and P1 supercars, plus followon
models (see “Learn More”).
High-performance, high-volume in Žebrák
The Czech Republic was chosen for MCT’s high-volume manufacturing
because it offers a central, easy-to-visit location for key
56 SEPTEMBER 2015
CompositesWorld