Ink-jet system speeds up process to prototypes

A new system of rapid prototyping in which complex metal components can be ‘printed’ directly from CAD data has been developed by a German research institute.

The Fraunhofer Institute for Manufacturing Engineering and Advanced Materials Research in Bremen uses a nozzle system similar to that used by ink-jet printers, which sprays glue onto metal particles to bond them into shape.

Rapid prototyping systems allow the prototype to be built up as a series of layers from a CAD model, tested and modified, allowing the final product to be developed more quickly.

Researchers have been seeking to widen the range of materials in which prototypes can be made.

An example is selective laser sintering. In this process, a laser is used to bond a polymer or particles of powdered metal to form a prototype or pattern for the manufacture of the end product.

In selective laser sintering, the particles of metal powder are pre-coated with an epoxy resin which melts under the action of the laser and glues the particles together.

Haiko Pohl of IFAM’s Near-Net-Shape Production Technologies department said that in the new system the prototype is built up by spraying an adhesive onto the layers of powdered metal.

The ‘print’ head squirts the binding agent onto a thin layer of powdered steel, bonding the particles together. The first bonded layer is then layered with more powdered metal and the next section is formed. In the next step of the process the still rather delicate object is given more strength and density. This is done by blowing away surplus metal powder and applying heat to remove binding agent from the surface.

The object or prototype is then infiltrated with molten bronze, which is allowed to gradually seep between the particles of metal, causing the binding agent to vaporise and at the same time strengthening the object.

In the final stage, various standard metalworking techniques are used to give the part its ultimate form.

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