One of the lesser-known 3d printing technologies is sheet lamination, sometimes also known as laminated object manufacturing (LOM). It is considered additive because one sheet of material is bound to another in a layer-by-layer process. The LOM process fused layers (usually of paper with a binding agent) using heat and/or pressure to bind the layers together. Like sheet lamination, a laser or a cutting blade removed excess material to achieve the final shape.
This technology was primarily used for prototyping or “look and feel” proofs of a design. Because of the binding agents, parts often had wood-like properties and could be sanded and painted. One drawback of this technology is that material waste can be high, depending on the object design.
One of the early developers of this technology was Solido, but the company is no longer is business. An Ireland-based company, Mcor Technologies Ltd developed a variation of the lamination process, but the company also seems to be no longer in business. At one point, EnvisionTEC offered a lamination system, but it no longer does so.
The main company left in this part of the industry is Fabrisonic with its variation on LOM using ultrasonics. Known as Ultrasonic manufacturing (UAM), this company works with metals rather than paper materials.
UAM is ultrasonic welding on a semi-continuous basis where solid metal objects are built up to a three-dimensional shape through a succession of welded metal tapes. Periodic machining operations deliver detailed features and form into the object until a final geometry is created.
The technology behind ultrasonic metal welding has been around since the 1950’s. 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 a scrubbing motion of the mating faces. This shearing motion cleans off surface oxides through friction, then allows direct contact of pure metal on pure metal. This process results in a solid-state atomic bond with minimal heating. Ultrasonic welding can be accomplished at very low temperature and without special environments. In aluminum for example, this peak temperature is always below 250 °F.
The solid-state nature is a key advantage of UAM 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. Metal foils are widely available on the open market for prices approaching that of billet.
–Creates bonds between dissimilar metals without creating an undesirable brittle metallurgy. This capability differentiates UAM from fusion based processes and enables the machine 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 embed into solid metal without the damage incurred incomparable fusion based additive processes.