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The Mechanical Engineering Technology department (MET) at Red River College have developed a new means of making dissolvable mandrels and patterns.
Leon Fainstein and Serge Broeska have developed rapid prototype composite tooling in an effort to make composite manufacturing more economical by eradicating the need for CNC machines as well as special machinery to make the mould.
Broeska says that rapid prototype composite tooling involves only a 3D printer, to make dissolvable mandrels and patterns and it can make complex wet layup or prepreg composite parts at any scale of commercial operation. He goes on to explain that a Computer Aided Design (CAD) model must be imported into the 3D printer software which will print virtually any shape in approximately 4 to 8 hours to meet the capacity of the build tray, although the mandrels or patterns can be divided in sections and assembled afterwards. The media the 3D printer uses is a dissolvable plaster with a binder mixture.
Broeska describes making complex composite parts using dissolvable mandrels as a simple process whereby first the mandrel is designed, printed and coated with polyvinyl acetate (an agent that prevents mandrel integration into the carbon fibre), then the mandrel is then laid up with wet layup or prepreg, vacuum bagged and cured. After curing the mandrel can be dissolved and broken away by submerging it in water.
To demonstrate the complexity of the composite parts that can be produced using this technique, the MET made a pair of “time trial” bicycle handlebars in the lab at Red River College using CAD software, the 3D printer, vacuum bagging materials, curing supplies and a kitchen oven.
“Where manufacturers require a permanent composite mould for short production runs they can make them with dissolvable patterns. These composite moulds can be very complex, have smooth surfaces and are comparable to metal moulds with the notable exception that they are much cheaper. In the Red River College lab a bicycle waterbottle cage composite mould was made along with a two part composite tool for an airfoil shaped bicycle down tube” said Broeska.
Rapid prototype composite tooling has been designed to allow production parts to be changed just as easily as the CAD model meaning parts can be readily fabricated and tested for physical properties or functional use until they reach acceptable properties, subsequently lowering the cost of research and development. This allows manufacturers to make smaller production runs, or specialty parts without the need to invest in traditionally made and expensive composite tooling.
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