Products include keypads,
bumpers, boots, covers, wipers, gaskets,
housings, bolts, nuts, insert-molded items; the
list is only limited by your imagination.
Molds for castings can be made several ways:
From a master:
(SLA, machined, supplied by the customer)
Molds can be made by
casting around a master using either silicone
or polyurethane material. The choice of
material depends on the level of detail, mold
life and what material will be used to cast
the replicated parts. Silicone is often used
for the mold if great detail is needed and
urethane will be used for replications.
Polyurethane may be used for the mold if
silicone is being used for the replications or
the mold longevity are the most important
factors.
Molds can be directly
machined into acrylic:
This method is used if a
CAD file can be provided and the part design
is finished. For simpler part designs, this is
a way of making a multiple cavity mold to get
quantities of parts cast without waiting for
the long lead-times and the high cost of
automated high-pressure injection mold
tooling. These types of molds are often the
choice for pre-production molding, or
production molding if the life of the project
is in the thousands rather than the
hundreds-of-thousands range and the cost of
injection-mold tooling is prohibitive. The
advantage of acrylic molds are the long mold
life, parts can be cast from either silicone
or polyurethane, very quick lead-time and cost
effectiveness.
MATERIALS:
Silicones:
Silicone rubber, a
synthetic polymer, has a strong silicon-oxygen
chemical structure that gives the elastomer
its unique performance properties. The process
of vulcanization transforms this structure,
allowing the silicon-oxygen polymer to become
an elastic rubber which allows it to withstand
a wide range of temperature extremes as
needed.
Silicone rubbers have high tear
and tensile strength, good elongation, great
flexibility and a durometer range of 5 to 80
Shore A. Softer durometers are available as
reinforced gels.
Silicones exceed all comparable
materials in their insulating properties as well
as flexibility in electrical applications. They
are non-conductive and maintain dielectric
strength in temperature extremes far higher or
lower than conventional materials can handle.
Silicones can be formulated to
comply with FDA, ISO and Tripartite
biocompatibility guidelines for medical
products. They are odorless and tasteless, do
not support bacteria growth, and will not stain
or corrode other materials. Most importantly,
silicone rubbers exhibit superior compatibility
with human tissue and body fluids.
Silicones resist water and many
chemicals, including some acids, oxidizing
chemicals, ammonia and isopropyl alcohol.
However, silicones should not be used with
concentrated acids, alkalines and solvents.
Polyurethane:
This category covers
an extremely wide variation in physical and
mechanical properties. Polyurethane polymers,
produced by the reaction of polyisocyanates
with polyester or polyether-based resins can
be either thermoplastic or thermosetting. They
have outstanding flex life, cut resistance,
and abrasion resistance. Some formulations are
as much as 20 times more resistant to abrasion
than metals. It is a unique material that
offers the elasticity of rubber combined with
toughness and durability. Because urethane is
available in a very broad hardness range it
allows the engineer to replace rubber, plastic
and metal with the ultimate in abrasion
resistance and physical properties.
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