1. Locally optimizing mechanical properties
3D printing, especially additive manufacturing of metals, has been hailed as a revolution in the manufacturing world due to its short cycle times, almost non-existent set-up, and unprecedented design freedom, even allowing to make complex structures such as fine lattices impossible with classical machining.
For implants such as spinal cages and total replacement hip joints this added design freedom and lattice structures has been used to great effect. The lattices not only allow anchoring of the implants through bone ingrowth but also locally reduce the stiffness of the implant to prevent complications resulting from bone degradation.
This capability can be broadened if we can combine 2 or more metals in a single structure. Even within material families, like the Titanium alloys used in implants, there are significant differences in properties. For instance, the Grade 5 Ti6Al4V titanium is well known for its higher strength but lower ductility, while the commercially pure grade 1 has excellent ductility and low e-modulus. With multi-metal printing, the lattices could be printed in the latter alloy while the load-bearing parts can be made in a stronger alloy.
Wear resistance
Friction is the enemy of moving parts. Not only will friction make the movement less efficient, it can also lead to premature failure due to wear. There are 2 ways to solve this: lubrication and using hard wearing materials.
Self-lubricating materials, such as brass and bearing metals, are often soft and don’t have the mechanical resistance to be load-bearing. Hence plain bearings are often used as inserts, which can get lost or trap dirt. With multi-metal AM one can, however, print a lubricating surface inside a construct, guaranteeing long-term smooth movement.
Hard-wearing materials, on the other hand, are often brittle and have a low tensile strength or shock resistance. These are often brazed into larger constructs such as cutting heads to improve the lifetime. Here the joining between the 2 materials becomes an issue. With multi-metal AM Gradients can be generated, gradually increasing hardness. As both high strength and high wear resistance can be combined without the weak point of a joint or sudden transition.
Vibration dampening
Those who enjoy watching the cycling classics will be well aware of the rigors of the hell of the north. However, they might not be aware of the science that has governed this race during the past 2 decades. For the cobblestones of Paris Roubaix, the bike frames of the top teams are optimized to filter out the high-frequency chatter to improve the rider’s endurance and performance. And this has had a clear impact on the podium of this race.
The same holds in many mechanical constructs. Using lattices and frames vibration resilience has been combined with stiffness since the great Eifel tower. However, those structures were built with a single material. Imagine that you could go a step further, and choose where to place braces that are stiff, and others that allow the sway caused by the wind to harmlessly flow away. With multi-metal 3d printing, this becomes an option, even going further and offering the possibility to add in locally compliant features.
Strength
Strength is often the critical parameter determining material choice and part design. With 3D printing optimizing designs for maximal strength has become summon ground. The organic structures generated by topological design optimize stresses through a single material part through modeling of the loads. Imagine if, in those models, you could single out the high-stress points and allocate higher strength values to them. How much more elegant and lighter structures could become. With multi-metal printing, this is no longer a pipe dream.
2. Improving chemical and physical performance
As technology progresses we demand more and more of the tools we use. Higher temperatures, faster processing speed, more aggressive media, … All these require high-performance tools. And with this comes specialty material. However in many of the use cases more than one use parameter influences performance. This often leads to a compromise, choosing a tool material good enough for both / all demands, but not the best for each individually. With multi-metal printing, this kind of compromise might no longer be a necessity. Below are some use cases describing how his new technology might be of aid to get more out of life.
Thermal conductivity
In terms of functional performance, the thermal behavior of tools is often a critical parameter. Often a compromise must be made between mechanical and thermal properties when selecting a material. The ability to create multi-metal parts can make the need to choose obsolete.
Rocket and injection nozzles, brake calipers and rotors, different types of complex forms of heat exchangers, heat sinks, and heat pipes are great examples of use cases where thermal conductivity can be improved by Multi- Metal AM.
Electrical conductivity
Aerosint is actively involved in a Eurostars project to print thermocouples and heating wires into aerospace-grade sensors. In order to make this a reality insulators must be printed in place to pursue the function of these added features.
From an industrial perspective, L-PBF of ceramics is still out there, blue sky technology. But this is because one looks at monolithic ceramic parts. Thin layers of insulator, which don’t need to be perfect from a mechanical point of view, is a different ball game. In fact, glasses and thin ceramics have been successfully processed by others.
Corrosion resistance
AM allows making complex structures, including ones with lots of internal channels. For his reason, metal printing is popular for heat exchanges. However, as channels become more complex, fouling and corrosion also become more troublesome. And corrosion is difficult to avoid if different metals are used in a single cooling circuit. Using multi-metal AM the surfaces in a cooling circuit in contact with the cooling medium can in parts produced using this technology easily be matched to other components. Adding small amounts of copper to these surfaces can also prevent the growth of algae, clogging fine tubes.
Aesthetics
Multi-Metal prints can be very aesthetically pleasing. It is no surprise that the unique appearance can therefore be appealing for luxury items. Indeed, you can now create watches, rings, bracelets, and many other accessories with custom patterns in the material itself. Sporting goods can be another example where multi-metal AM allows a huge range of customization opportunities while potentially even improving performance.
Interested ?
They are many exciting possibilities with Multi-Metal, reach out and talk to one of our experts: contact us.
