3D printing has already had a disruptive impact on the world of manufacturing by allowing parts to be made faster, made with never before seen complexity and brought to market in less time.
Ultrasonic additive manufacturing (UAM), developed by Fabrisonic, combines a unique room-temperature metal deposition process with the ease of traditional CNC milling. Our patented ultrasonic print head is integrated into three-axis mills to create a hybrid additive-subtractive process. Swapping from additive to subtractive is as easy as doing a tool change.
So, how does it work?
Welding Metal with Ultrasound
Ultrasonic metal welding has been around since the 1950s with modern applications in everyday welding of battery tabs, thin foil packaging and even electronic wires. An ultrasonic weld operation begins by pressing a thin metal foil onto another metal component. While under a constant force, ultrasonic vibrations are applied to cause scrubbing of the mating faces. This shearing motion cleans off surface oxides through friction to allow direct contact of pure metal on pure metal. The result is in a solid-state atomic bond with minimal heating.
The heat and plastic deformation promote diffusion and recrystallization at the interface, resulting in a true metallurgical bond. Ultrasonic welding can be accomplished at very low temperature and without any special environments. For all metals, the bonding temperature is significantly below their respective melting temperature. In aluminums, for example, this peak temperature is always below 250°F. The solid-state nature is a key advantage of ultrasonic welds as it:
- Protects material properties of the incoming feedstock. Since the materials are only slightly heated, the materials do not experience changes in grain size, precipitation reactions or phase changes. The properties of the incoming feedstock are the same as the properties of the final part.
- Creates bonds between dissimilar metals without creating an undesirable brittle metallurgy. This capability differentiates UAM from fusion-based processes and enables Fabrisonic to print engineered materials with custom material properties or properties to match an existing component. For instance, layers of molybdenum and Invar can be printed into an aluminum heat exchanger to match the CTE of a mounted electronic circuit.
- Embed temperature-sensitive components in solid metal parts. Many electronic components (including microprocessors, sensors and telemetry) have been successfully embedded in solid metal parts using UAM. The low-temperature bond allows delicate components to be embedded in solid metal without the damage incurred in comparable fusion-based additive processes.
Ultrasonic Additive Manufacturing (UAM)
UAM is ultrasonic welding on a semi-continuous basis where solid metal objects are built up to a net three-dimensional shape through a succession of welded metal tapes. Through periodic machining operations, detailed features are milled into the object until a final geometry is created by removing excess material. The figure at right shows a rolling ultrasonic welding system, consisting of two 20,000 hertz ultrasonic transducers and the welding sonotrode.
High-frequency ultrasonic vibrations are locally applied to metal foils and held together under pressure to create a weld. The vibrations of the transducer are transmitted to the disk-shaped welding sonotrode, which in turn creates an ultrasonic solid-state weld between the thin metal tape and the substrate. The continuous rolling of the sonotrode over the plate welds the entire tape to the plate. Successive layers are welded together to build up height. This process is then repeated until a solid component has been created. CNC contour milling is then used to achieve required tolerances and surface finish.
Hybrid: What is That?
UAM combines the advantages of additive and subtractive fabrication approaches to allow complex 3D parts to be formed with high dimensional accuracy and smooth surfaces, including objects with complex internal passageways. ASTM International defines additive manufacturing as the “process of joining materials to make objects from 3D model data usually layer upon layer as opposed to subtractive manufacturing methodologies much like CNC milling.” Synonyms include: additive fabrication, additive processes, additive techniques, additive layer manufacturing, layer manufacturing and free-form fabrication.
While not formally defined under ASTM terminology, hybrid additive is generally considered to be a combination of additive (3D printing) and subtractive (CNC milling) technologies in a single machine. For instance, the SonicLayer 4000, starts off life as a large three-axis mill to which we integrate our patented ultrasonic welding head. The system builds up to near-net shape using ultrasonic welding and completes fine detail through the use of onboard CNC milling.