DfAM to optimise parts.

What is DfAM?

Designing for Additive Manufacturing (DfAM) is the process of designing a component so that it takes advantage of the Additive Manufacturing layering process, ensuring that the component delivers functional benefits within the supply chain that could not be achieved through conventional production techniques.

 

Designing for Manufacturing (DfM)

For decades Designers and Engineers have developed parts and prototypes under the restrictions of their production capabilities. Whether the production techniques involved CNC Machining, Castings, Milling or other conventional techniques, the design of the part or prototype would be limited to the manufacturing process methods where usually material is removed from a billet (subtractive manufacture), followed by other processing steps such as folding, welding and assembly to form the final component. Therefore designs would be orientated around Designing for Subtractive Manufacture (DfM).
The conventional barriers on traditional manufacturing meant that the production of components could take a long time, especially multi-part components with complex assembly as tooling production would also be required. The subtractive production methods can also result in high amount of waste from the production lines.

Designing for Additive Manufacturing

 

Design Freedom

Designing for Additive Manufacturing takes advantage of the metal 3D printing process to produce a complex part. The AM process offers far less design constraints than that of conventional manufacturing processes, thus AM is often described as having design freedom. AM produces parts by adding material where it is required in a part, often to create an overall geometric shape which has areas that could not be reached or achieved by subtractive manufacturing. For AM the design freedom allows for material to be placed around fixing points, along areas required for strength, to form freeform channels, deposition of varying amounts of material without tooling to add value to the component through improved function, light weighting, decreased tooling costs and multi-part to single part. The enhanced design freedom of AM allows complex parts to be developed with benefits that conventional methods or other CAD/CAM processes could not deliver.


Improving Functionality through Design: Case Study

3D printing in metal can deliver innovation through a new product, prototype or an improved product. Alterations to a design or new designs that focus on delivering a more efficient function add the greatest value. An example of this is in the development of a latticework cone filter. Here the aim was to improve the efficiency of the filter by maximising the open area: through firstly decreasing the diameter of the strands in the latticework. When fluid is passed through a filter, turbulence is created and the resistance across the filter increases. To reduce this turbulence the apertures in the design were aligned to increase the laminar flow through the filter. Tests determined that these design changes reduced the resistance of the filter compared to a comparable conventional filter demonstrating that the filter AM design added value. Further modification of the Additive Manufactured latticework design allowed the incorporation of smaller aperture sizes, thus achieving a different filtration level whilst maintaining strength in the filter.

Considerations for DfAM

Whilst parts that have been designed for subtractive manufacture can be manufactured by AM, these designs may not be optimised for AM production. For powder bed AM technology, where a laser melts the powder according to the sliced layer of the CAD design, anchor supports are required to attach the component to the build platform and build supports are required for overhanging areas of the part. The AM process produces a near net shape part, whose surface finish is rougher than a machined finish. Critical features such as surface roughness on certain facets of the part, hole dimensions and other part specifications should be identified prior to part manufacture.
Croft uses its AM knowhow and knowledge to assess the suitability of CAD designs for manufacture by metal 3D printing and can offer advice on optimisation of CAD designs for subsequent AM production.

Reverse Engineering

The CAD capabilities twinned with the layering process of AM offers the ability to Reverse Engineer components previously manufactured by conventional methods. Re-engineering the part could enhance how the part performs, whether that is through a reduction in weight (lightweighting) or through producing a multi part component already assembled.

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