Lesson 8.9ShapeChapter 8 · Additive manufacturing

Ultrasonic additive manufacturing (UAM)

Ultrasonic vibration welds metal foils without melting, then a mill trims them (sheet lamination)

Ultrasonic additive manufacturing (UAM) builds metal parts by welding thin foils onto each other with high-frequency vibration. Nothing melts: the metal stays solid, much as two very clean metal surfaces can stick when rubbed hard together. Because it runs cool, UAM can bury sensors, wires and cooling channels inside solid metal.

Photo: Fabrisonic LLC, CC BY-SA 4.0, via Wikimedia Commons

ultrasonic additive manufacturing · welding and machining, 5 stepsLeft: the foils being welded, with the joint magnified below. Right: the machining step that follows. Circled numbers match the steps below.

How it works

Lay a foil. A strip of metal foil, typically about 0.15 mm thick and 25 mm wide, unrolls onto the part.
Press and vibrate. A sonotrode (a wheel-shaped horn driven by ultrasonic vibration) rolls over the foil. It presses hard and scrubs it side to side about 20,000 times a second (20 kHz).
Bond without melting. The scrubbing breaks the thin oxide film (a skin of tarnish) on both surfaces. Clean metal touches clean metal and the atoms bond, while the part stays warm, not molten.
Repeat. Foils are laid side by side and on top of each other, building a solid block layer by layer.
Machine and embed. Every few layers, a built-in CNC mill (a computer-controlled cutter) trims the outline and cuts channels or pockets. Sensors or fibers go into a pocket, and new foils seal them in.

Key facts

Materials: Aluminum alloys (most common), copper, titanium, nickel and steel foils; dissimilar pairs such as aluminum with copper or titanium
Typical parts: Heat exchangers with internal channels, parts with embedded sensors or fibers, multi-metal plates and transition joints
Part size: From a few centimeters up to roughly 1.8 m across on the largest machines
Precision: Set by the built-in CNC mill: about ±0.05 mm on machined faces
Surface finish: Machined, so as smooth as any milled part
Batch size it suits: Prototypes, one-offs and small series of high-value parts
Tooling and machine cost: No tooling. Machines typically cost from several hundred thousand to millions of dollars
Speed: Hours to days per part: welding is quick, but the machining stops add time

Strengths and limits

Strengths

No melting, so dissimilar metals join without brittle layers
Sensors, fibers and electronics survive being buried in metal
Internal channels with no supports or loose powder to clean out
Machined accuracy and finish from the same machine

Limits

Works best with softer metals; aluminum is by far the easiest
Bonds between foils can be weaker in the stacking direction
Mostly blocky shapes; thin, tall or intricate features are hard
Few machine makers and costly equipment

Where it's used

Aerospace and spaceHeat exchangers and thermal-control parts for satellites and aircraft
ElectronicsCold plates and housings with built-in cooling channels
Energy and researchStructures with embedded fiber-optic or temperature sensors
Heavy industryMulti-metal transition joints, such as aluminum bonded to steel or copper

How to recognize it

Blocky parts that look milled from solid, with no layer lines on the outside.
On a cut and etched section, thin stripes about 0.15 mm apart: the foil layers.
Two different metals in one block, such as aluminum on copper, meeting at a sharp, straight boundary.
Hidden internal channels or wires that no cutter could have reached from outside.

Compare with

Ultrasonic welding7.7the same vibration bonding used to join two parts; UAM repeats it foil after foil to build one.Laser powder bed fusion8.4also makes internal channels, but by melting powder, so it cannot bury sensors or freely mix metals.Milling5.2UAM has a mill built in; the final shape is cut, so accuracy matches milling.

Watch it

Fabrisonic3D · The maker explains how ultrasonic welding bonds foils without melting

Fabrisonic3D · Real footage of the machine laying, welding and trimming foils

Fabrisonic3D · Example parts: embedded sensors, internal channels, mixed metals

Fabrisonic3D · A large production machine at work

See real photos

Wikipedia: Ultrasonic consolidation — the process and its history; text only, no photos
Wikimedia Commons photo search

Remember

UAM welds metal foils with pressure and ultrasonic vibration, never melting them.
Low heat lets it join dissimilar metals and bury sensors inside solid metal.
It alternates welding and CNC machining, so parts come out accurate.