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Rapid Tooling & Metal Parts by Additive Fabrication (C) Copyright Castle Island Co., All Rights Reserved.
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 Tooling & Metal Part Technology Comparison Tables...
Injection Molds & Metal Parts Continued...
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Aluminum-filled Epoxy Tooling Aluminum-filled epoxy tooling is a good choice for short prototype or production runs for applications that require an engineering thermoplastic as a final material. It can be thought of as one step up from silicone rubber tooling, and while it's fabrication is similar in concept, in practice 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:
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Spray Metal Tooling
Spray metal tooling is made in a similar fashion to aluminum-filled epoxy tooling. In this case, an epoxy or low melting temperature metal alloy tool is prepared by casting this material against an RP-generated pattern. A thin metal coating is then arc-sprayed on the resultant mold's working surface to give it greater strength. Tool life is about the same as for aluminum-filled epoxy, but the method can accommodate larger parts.
Kirksite Tooling
Kirksite tooling is advantageous for more complex geometries, but it's generally less accurate and more expensive than aluminum-filled epoxy, or spray metal tooling. Kirksite is a zinc-based alloy and the tool making process also starts with an RP-generated pattern, but has more transfer steps than either of those methods. Kirksite tools have about the same life as spray metal or aluminum-filled epoxy tools.
Rapid Solidification Process (RSP) ToolingTM
Rapid Solidification Process ToolingTM was developed by the Idaho National Engineering and Environmental Laboratory (INEEL) in conjunction with several large corporations. RSP Tooling LLC was formed to commercialize the process. The company has partnered with Belcan for machine design and manufacture.
Molten metal is sprayed at high velocity onto a ceramic or polymer pattern which may be generated by rapid prototyping or in any other way. Stainless steel, tool steels, copper, brass, gray iron, invar, Kirksite, alloys and other metals can be used. As the metal droplets impact the form, they rapidly cool and harden.
This seems like a process that should be full of sound and fury, but it's surprisingly gentle, high in resolution, extremely fast, and yields metal properties that so far have been found to be superior to the intrinsic material. It's possible to coat a toy balloon with a thick layer of metal without bursting or melting it, to pick up fingerprints on a pattern, and do this at build-up rates of hundreds of pounds of metal per hour. Molds created with the process have been found to last as much as 20% longer than comparable machined molds of the same materials. After the pattern has been coated with sufficient material, it is removed and the resultant metal block undergoes final-machining to fit in a mold frame. Work is progressing to increase accuracy and mold size, and incorporate conformal cooling by interrupting the spraying process to embed copper tubing. One oft-mentioned limitation of the process is its inability to reproduce high aspect ratio features.
Raymor Industries, Inc. (Canada) supplies a similar process through its Advanced Powders & Coatings Division. Raymor calls its process Vacuum Plasma Spraying (VPS) and it can use a wide range of metals and other materials. The thrust appears to be more toward net-shape parts than tooling, however.
SprayformTM
The SprayformTM process is similar to RSP for steel tools and was originally developed by Sprayform Ltd. of the UK. Ford Motor Company purchased the firm, moved the entire operation to the US, and has applied its considerable resources to further developing the process. Several of Ford's own facilities are making metal tools using SprayformTM and the company has licensed it to Praxair Surface Technologies and a dozen other firms. At present the process uses a ceramic pattern, but work is ongoing to develop the use of RP patterns directly. SprayformTM is said to be well-adapted to large tools.
RePliForm
RePliForm offers a process that is based on electroforming. Although now used mainly as a finishing and strengthening method for plastic parts made by additive fabrication, it's still available as a tooling process, its original application.
A metal shell is plated on to a rapid prototyping-generated master. After the metal shell is electroformed, the pattern is removed and the hollow space is usually filled with a ceramic composite material which is temperature coefficient-matched to the shell. Either copper or nickel can be used to generate the face of the tool. RePliForm indicates that the main limitation on accuracy is the RP pattern itself. Depending on the plastic used, a copper tool can generate thousands of parts and a nickel tool as many as 50,000. The company feels the process is especially good for large parts.
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From Here...
Rapid Tooling & Metal Part Technology Comparison Tables.
Rapid Manufacturing; What RP will be when it grows up.
RP System Manufacturers.
Bridge Tooling and Related Listings.
Service Bureaus.
RP Technology, Brief Tutorial.
RP's Frequently Asked Questions.
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.