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Aluminum-filled epoxy tooling is a good choice for short prototype or production runs for applications that require a final
engineering thermoplastic. It can be thought of as one step up from silicone rubber tooling, and while it's fabrication is
similar in concept, in usage it's more complicated and expensive. Molds made in this way are used in injection molding machinery,
but as with RTV rubber molds, the parts fabricated won't be identical to those created in a high volume mold. Cycle time must be
considerably longer due to the poorer thermal conductivity of the material compared to metal, and lower pressures must be used to
accommodate its lower strength. The process works best for relatively simple shapes. Tool life is adequate for anywhere from 50
to 1000 parts, depending on requirements.
The following is a somewhat simplified description of the process, which has much in common with that used to fabricate an RTV
rubber mold. An RP-generated pattern is embedded in a wooden frame along a parting line. Aluminum-filled epoxy is poured around
it to create the first half of the mold. It's usually necessary to secure the positioning of the pattern with specially fabricated
wooden supports, and often specially machined metal inserts are placed in areas of the mold that might need strengthening.
The parting line might also be a fairly complex geometry rather than just a simple plane, requiring additional fabrication steps.
After the mixture hardens, the entire assembly is inverted and the second half of the mold is cast against the first. After the
second half of the mold is completed, the pattern is removed. Aluminum-filled epoxy molds are typically used in a mold frame and
water cooling lines can also be included during the fabrication process.
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