FOR AUTO RTM

PLANT TOUR
FIG. 1 Monocoque tubs via low-pressure RTM
The automated McLaren P1/MP4 monocoque manufacturing line uses actuated
six-piece tooling to mold the 70-kg, one-piece tub with integrated aluminum
attachments and hollow structural frames in a one-shot LP-RTM process.
FIG. 2 Automated pre- and post-mold handling
Robots place P1/MP4 preforms and remove the finished tubs, placing them into
the mechanized ceiling track for finishing operations.
monocoque “tubs,” aerodynamic structures and engine parts are
in various stages of layup, vacuum bagging, autoclave cure and
finishing. This building features two 2.5m by 4.5m autoclaves plus
eight ovens.
Design, development and prototyping activities all take place
in Salzburg, handled by a staff of 30 to 50 in design engineering.
Salzburg’s R&D labs develop processing methods and equipment,
including robotics, and also perform materials testing for mechanical
properties, degree of cure, fiber volume, porosity and characterization
of adhesive bonds and laminate failures. In addition,
MCT performs industry-standard tests for Class A surface finish
as well as environmental testing, using UV and climate exposure
SIDE STORY
Mini-autoclaves for visual carbon parts
Mubea Carbo Tech Salzburg’s Building 3 is the center for several of
the company’s mini-autoclave programs, including a carbon seat shell
for Porsche, which produces 16,000 parts (8,000 seats) per year in a
twin-cavity steel tool. A mini-autoclave is a part-shaped piece of equipment,
which integrates metal tooling and pressure vessel into a single
unit, dedicated to one part. MCT uses automated cutters and nesting
software to prepare prepreg kits for layup. Hand layed onto polyethylene
(PE) slip sheets, the layups are then transferred into the mini-autoclave
and vacuum bagged either with traditional vac-bag film or a reusable
bag. The mini-autoclave is then hydraulically clamped shut and vacuum
and 4 to 12 bar of air pressure are applied to compact laminate stacks
ranging from 0.5 mm to several centimeters in thickness during a heated
cure. Cycle times range from 15 to 60 minutes, depending on the size and
complexity of the part. “The size of mini-autoclave parts is limited by legal
requirements on pressure vessels,” explains Siegmann. “Once parts reach
the size approaching that pressure limit, you must have a vessel the size of
a normal autoclave.”
MCT Žebrák uses 60-80 mini-autoclaves (see photo), mainly for visual
carbon parts, says Karas, for example a 0.5m by 2.5m spoiler. “Customers
like visible carbon,” he adds, describing an MCT-patented transfer foil
technology developed for cosmetics. These foils used on the CFRP surface
Part-specific, short-cycle, high-pressure cure
MCT Žebrák has 60 to 80 mini-autoclaves in production, using vacuum and 4
to 12 bar of air pressure to compact and cure bagged prepreg layups in 15- to
60-minute molding cycles. Source | Mubea Carbo Tech
provide a clear coat finish without secondary operations. “But this is just
one possible way of achieving this,” notes Karas, who points out that
painted surfaces must be equally high quality. He says the reusable bag
technology used in the mini-autoclaves is also unique, developed with a
supplier using a special silicone and textile reinforcement. Slavko claims
each reusable bag can perform to specification for hundreds of cycles
before it must be replaced.
54 SEPTEMBER 2015
CompositesWorld