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Polymer Processing
Molding Papers
Hand lay-up process
1.
Brief introduction
Hand Lay-
up process is also called contact molding, which
job is to turn of the glass
fiber
fabric and resin in the mold shop, and then
solidified forming process for glass
fiber reinforced plastic products. In
China, hand lay-up process occupied about 80%
of all thermosetting resin matrixes
composite molding process in the gross domestic,
which
is
used
the
earliest
and
most
widely,
as
a
molding
method,
in
thermosetting
resin matrix composite material
molding.
2.
Process Description
(1)
Production Preparation
construction
site:
the
size
of
the
workplace
should
be
based
on
product
size
and
output decisions, the site demands
clean, dry and well ventilated, the air
temperature
should
be
maintained
at
between
15
~
35
℃
,
after
processing,
renovated
section
should include a dust extraction and
sprinklers.
Mold
preparation:
preparation
work
including
cleaning,
assembling
and
coating
release, etc.
Resin glue make-up:
we
should pay attention to two problems:
①
The glue should
prevent air bubbles in the mix;
②
Assigned glue
amount can not be too much, each amount should
ensure it become
the resin gel before
running out.
Enhanced
material
preparation:
to
enhance
the
types
of
materials,
the
choice
should relate to the
requirements and specifications.
(2)
Paste making
and solidification
There
are
two
kinds
of
hand-laminated
paste
making,
namely
wet
and
dry.
Dry
stacking
is
to
use
pre-preg
cloth
as
raw
material,
a
good
first
material
(fabric)
by
sample
cut
into
a
bad
material,
layer
softens
when
heated,
and
then
level
by
level,
close
to
the
mold,
and to
rule
out
interlayer
bubbles,
so
that
dense.
This
method
is
used for pressing cans and bags of
pressure molding.
Shop wet layer is
directly
put reinforced material cord
in the mold, close to the die
level
by
level,
the
less
bubbles,
to
make
it
dense.
Hand
lay-up
method
has
been
applied
more
generally
craft
shop
floor.
Shop
floor
wet
gel
coat
layer
is
further
divided into the
system and structure of the layer of paste paste
system.
In
addition,
the
hand
lay-up
tool
to
ensure
product
quality
greatly.
Generally
have
wool roller, roller
bristles, spiral rollers, and electric saws,
electric drills, grinding and
polishing
machines.
Products
cured
sub-hardening
and
maturation
in
two
stages.
Triangulation
from
the
gel to a
general 24h, at this time curing degree of 50% to
70% (Barcol hard degree 15),
may be
stripping, de-cured under natural environmental
conditions after 1 to 2 weeks
in
order
to
make
products
with
the
mechanics
strength,
said
the
aging
of
its
curing
degree of 85% or more. Heating can
promote the ripening process, pairs of glass fiber
reinforced
polyester,
80
℃
heating
3h,
pairs
of
glass
fiber
reinforced
epoxy
after
curing
temperature
can
be
controlled
at
150
℃
or
less.
Heat
curing
many
ways,
small and medium products can be heated
during the curing oven curing, large-scale
products can be used in-mold heating or
infrared heating.
(3)
Stripping and finishing
Stripping
is
designed
to
ensure
products
free
from
injury.
Stripping
method
has
the
following
several kinds:
①
the die on top of a stripping ejector
embedded devices, stripping when the rotating
screw, the product ejection.
②
pressure
ejection
of
compressed
air
or
water,
leaving
mold
on
the
entrance,
stripping
will
be
compressed
air
or
water
(0.2MPa)
between
the
pressure
into
the
molds
and
products,
while
wood
hammer
and
rubber
hammer
to
fight,
so
that
separation of products and molds.
③
large-scale
products (such as boats) stripping can take
advantage of jacks, cranes
and hard
wedge tools.
④
complex
products
can
be
used
hand-stripping
method
first
paste
in
the
mold
system
of two three-story glass fiber reinforced plastic,
can wait until the cured peel
from
the
mold,
and
then
continue
to
paste
the
system
on
the
mold
to
the
design
thickness, cured easily from the mold
off down.
Finishing can be divided
into two kinds, one is the size trimmed, the other
is the
bug fixes.
①
Size trimmed is
after molding products, according to design
dimensions to cut out
excess
superfluous parts;
②
bug fixes, including
perforation repair,
air
bubbles, cracks, patches,
broken hole
reinforcement and so on.
3.
The characteristics of Hand lay-up
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