Composite Thinking: breaking out of the limits of 3D printing
Composite 3D Printing (3DP) is most often used to describe either multi-material 3D printers from the likes of Stratasys, or materials with secondary material infill such as Markforged offer.
There is however, a much simpler and more obvious route to a “composite” part: Adding inserts or components of other materials after printing. In its simplest form this might be the inclusion of a standard nut or bolt within the part but there could be a lot more. For production 3DP parts the combination of additive manufacturing and traditional techniques has enormous potential.
3D printing is inherently a relatively expensive process. The cost of a 3D printed part can easily come to between a hundred and a thousand times the raw material cost, so it is clear that it is necessary for production parts to add significant value to become viable. In fact, a 1cm cube of DLM printed aluminium can cost upwards of £5 whereas a section of aluminium bar the same size might cost £0.04. If the same cube was hollow the cost of the 3DP part might be the same but the material cost might be only £0.004. While 3DP polymers are significantly cheaper than 3DP metals, the still represent a high premium versus the raw material.
Despite possible additional assembly costs, combining standard or pre-existing components with 3DP parts to create ‘composite’ parts will typically have significant cost savings over ‘printing the whole thing’.
Designing for production 3DP should not exclude traditional manufacturing methods.
It is widely understood that design should take into account the manufacturing process, and whilst in 3DP the design parameters are particularly unique, design without consideration of including other techniques and materials would be unwise. In some applications, the 3DP material may not give the desired properties. Whether the application calls for heat dissipation, strength, flexibility, electrical conductivity, impact resistance or any other properties, there are often more suitable materials to aspects of a design outside of 3DP but the form or envelope itself requires 3DP.
The complexity of form which 3DP allows, empowers the designer to consider the 3DP component as an interface component enabling the use of multiple materials and manufacturing components exactly as the application requires.
Laser cutting, in particular, has significant compatibilities with 3DP parts. Sheet materials are typically relatively cost effective, as is laser cutting, which also allows complex shapes (even if only in 2 dimensions). The ability to design easily assembled components with a snap fit or complex interlocking joints with minimal assembly cost is a key benefit of this composite thinking.
With the relatively high costs of metal 3DP, it is also a great example of where the smaller the 3D printed metal element, the lower the total component cost. Utilising 3DP only where it adds the most value greatly increases the potential for viable production parts.
In short 3DP technology adds a very useful ‘tool’ to the toolbox available to the design engineer – complementing existing manufacturing methods, unlocking design freedoms to create previously unavailable superior production parts.
Case study: – Bearing Cages and Triple Labyrinth Seals
Two examples of where Bowman Additive Production (Bowman AP)have been able to combine the complex geometries and design flexibilities of SLS printed Nylon with laser cut metal inserts to create entire product ranges of high-performance engineering components.
In both cases, while the SLS nylon 11 material allows otherwise impossible, performance enhancing geometries and the flexibility to allow parts to clip together, the limiting factor was wear. Running at speed against metal components can result in a high wear rate in the Nylon. The solution was to design voids within the 3D printed parts and insert laser cut bronze or stainless steel pieces to virtually eliminate any wear of the 3D printed Nylon component.
Bowman AP’s Composite 3D printed Cage design can outperform traditionally manufactured components by 30-40% in load rating and 300% in life rating.