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Bobbin Friction Stir Deposition

A solid-state additive process for large metal structures.

Developed by Zachary Courtright at NASA, exclusively licensed to LeapFast, and covered by US Patent 12,157,179 B1.
Created to bring the benefits of additive manufacturing to large aerospace and defense structures: design freedom, part consolidation, material savings, seamless multi-material structures, extremely high deposition rates, and repair at the point of need.
Modular end-effector runs on existing friction stir welding equipment, so one machine performs multiple processes.

Process videoA B-FSD deposition trial in progress, shown from two angles.

Close-up of an aluminum plate with four stacked passes of B-FSD material along its edge, with curved tool rotation marks across the top pass — Four-layer sampleFour layers of B-FSD material built up along the edge of a plate. The arcs are the tool's rotation marks.

Aluminum domeA seamless aluminum dome, built entirely with B-FSD and shown in blue.

In the missileSchematic cutaway of a stage: the oxidizer tank sits above the fuel tank, each closed by domed bulkheads. The domes, shown in blue, are the aluminum parts B-FSD can build.

01 · FEED

Aluminum Feedstock Goes in From the Side

It enters an open volume between the containment block and the edge of the part.

02 · STIR

Consolidated Below the Melting Point

Crown and root shoulders clamp the plane while the pin drives plastic flow. Nothing melts.

03 · BUILD

Pass by Pass to Net Shape

Each pass extends the part in-plane, so rings, barrels, and domes grow without a forging die.

Value proposition

Forging-Quality Structures, Without the Forge.

B-FSD gives large aluminum parts the strength of a forging without the die, the long lead time, or the minimum order.

SPEED

Days to Weeks, Not Months

No inflexible forging die or casting pattern to make, and no queue behind one.

STRENGTH

Forge Equivalent

A fine as-built microstructure with no solidification porosity or hot cracking.

FLEXIBILITY

Economic From One Part

No tooling to pay off, plus design freedom, part consolidation, and seamless multi-material structures.

REPAIR

Fix It Where It Stands

Repair and feature addition on parts already in service, at the point of need.

How it works

Solid-State, Pass by Pass

01 Feedstock Enters Through the Containment Mechanism
Aluminum feedstock is fed laterally into an open volume bounded by the containment block and the substrate edge. Crown and root shoulders clamp the plane; the pin between them drives plastic flow. Peak temperature stays below the alloy's melting point.
02 Material Consolidates Against the Substrate Edge
The root shoulder reacts the crown shoulder's load through the workpiece, so no backing anvil is required. Tool and containment traverse together along the edge; each pass extends the part in-plane rather than stacking a layer on top.
03 The Part Is Built to Net Shape and Inspected
B-FSD builds net shape, with no post-build machining.

Because nothing solidifies from liquid, the deposit has a wrought, fine recrystallized microstructure, not a cast one. No solidification porosity. No hot cracking.

Labeled diagram of the B-FSD tool: a rotating spindle through the containment mechanism, crown and root shoulders on either side of the substrate, feedstock fed in from the side, and the new deposit forming at the substrate edge, with an inset showing the containment's open volume for deposition — The B-FSD process schematic. Feedstock enters through the containment mechanism, the crown and root shoulders clamp the substrate, and the deposit forms at the substrate edge. The inset shows the containment's open volume in which material is consolidated.

Why solid-state

The Net-Shape Deposit Never Melts. That Is the Whole Argument.

B-FSD plasticizes metal below its melting point and consolidates it under forging pressure, which is why the comparison below runs the way it does.

Criterion	Forging	Casting	B-FSD
Lead time	Years	Months	Days to weeks
Hard tooling	Dedicated die per geometry	Pattern and mold	None
Porosity & hot cracking	Low	Inherent risk	None (no melting)
High-strength Al (2xxx/7xxx)	Standard	Poor castability	Forge equivalent
Multi-material structures	No	Limited	Seamless multi-material
Process loads	Very high press loads	None	Low; self-reacting tool
Machining	Extensive	Complex	N/A
Thin-wall structures	Limited by die	Limited by flow	Enabled
Equipment	Large press	Foundry	Modular end-effector on existing FSW equipment
Minimum economic quantity	Volume amortizes the die	Volume amortizes tooling	One
Point-of-need repair	No	No	Yes

Questions engineers ask

Straight Answers

Do We Need to Buy Any Equipment?

No. You send us a drawing, and we manufacture the part. B-FSD runs on existing friction stir welding equipment, so LeapFast can deposit structures and solve your joining needs with the same equipment.

Is the Deposit as Strong as a Forging?

Yes. B-FSD is forge equivalent: a wrought, fine microstructure with no solidification porosity and no hot cracking.

Can You Deposit Onto an Existing Part?

Yes. Repair and feature addition onto existing aluminum structure is a core application (it is one of the reasons the process was invented).

How Is a Part Qualified?

To AWS D17.4 or to your specification. LeapFast qualifies friction stir welding procedures to AWS D17.4 and to NASA specifications, including for production flight hardware. LeapFast is also helping write the industry specifications for B-FSD. Work starts with a paid feasibility study and an agreed first-article plan.

Who Owns the Process?

B-FSD was developed by Zachary Courtright while at NASA. LeapFast holds an exclusive license to the NASA process and US Patent 12,157,179 B1.

Next step

Can You Make Your Part Using B-FSD?

Send a drawing or a STEP file. We come back within 3 business days with a manufacturing architecture and a rough cost delta, including when the answer is no.

Request a Quote

contact@leapfast.com (330) 242-6951 252 W Boardman St, Youngstown, OH 44503