Until recently the outer geometry of a part and its function and/or strength were of main interest for the user, but Additive Manufacturing allows the integration of additional functions and new fields of application of technical parts.

One example of the ability of AM technology to integrate functionality directly into parts is in the production of moulds or tools with conformal temperature control or vacuum channels running directly below the surface of the die. An example of an extrusion tool design with this feature is described in this case study. The cooling channels in this tool cannot be produced with any other technique.

Basic cell geometries for structure design

Another good example of using AM to integrate functionality can be seen in parts with repeating internal patterns which enlarge inner surfaces for a better energy or mass exchange in devices for heat recovery or filtration. Some examples of unit cells for 3D tessellation are showed above. These structures make possible the complete filling of the space, if needed, allowing the free design of part density.

Additively manufactured study for material combinations of porous and dense areas. Shown in the left image is a dense shell with a porous core and on the right is a porous shell with a dense core

To further utilise the full potential of metal AM techniques, complex internal structures can be combined with other geometric features as outer shells. Separating parts into shell and core volumes enables new solutions, not only for lightweight parts which need a dense shell and a porous core, but also for parts with internal functionality. Both parts were produced in one manufacturing step, resulting in considerable savings in part weight as well as energy consumption during processing.

The frame of this bike has been made using Additive Manufacturing. Built from Ti alloy the frame is 33% lighter than the original. The build plate (right) includes all parts for the frame (Courtesy Renishaw & Empire Cycles)

The design process can also incorporate the use of topological optimisation software to determine the logical place for material. Material is removed from areas of low stress until a design optimised for load bearing is finalised. The resulting component is both light and strong. This process was applied to parts of the bike frame shown above. The optimisation of the design and the use of titanium alloy resulted in a weight saving of 33% over the original.

Due to limited building envelopes of AM systems, the production of large structural elements by AM is restricted. The size of the current maximum build space in industrially available AM equipment is approximately 630 x 400 x 500 mm, but AM technologies are being continually improved and build space in all systems will certainly continue to grow.

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