Skip to content
MecAgentMecAgent
Lesson 4.7DeformChapter 4 · Sheet and tube forming

Superplastic forming

Hot gas blows a superplastic sheet into one die

Superplastic forming (SPF) heats a special fine-grained sheet until it can stretch to several times its length, like warm bubble gum. Gas pressure then blows it slowly into a one-sided die (a shaped steel mold). It turns one sheet into deep, complex panels, such as aircraft doors and sports-car bodywork, that would otherwise need many pieces.

Superplastic forming: a real photo
Photo: San Diego Air & Space Museum Archives, Public domain, via Wikimedia Commons
Gas pressure slowly blows a hot, superplastic sheet into a one-sided dieCross-sections of the heated press at three moments, read left to right. Aluminum or titanium sheet, argon gas.Clamp and heatgas inlethot platenlidflat sheetempty cavitydieventhot platen12aluminum 450–520 °Ctitanium about 900 °CBlow with gas34air outargon at about 10–30 barslow: minutes to hoursOpen and remove5thinnest inthe cornersthe sheet copies the die;trim off the flangesheet (workpiece)die, lid and pipeheatersargon gasmotion
superplastic forming · clamp and heat, blow with gas, open and removeRead the panels left to right; circled numbers match the steps below.

How it works

  1. Clamp the sheet. A flat sheet of superplastic alloy is laid over a die with a cavity (the hollow shape of the part). A sealed lid presses on its edge, making a gas-tight seal.

  2. Heat everything. Heated platens (hot press plates) bring die and sheet to forming temperature: about 450–520 °C for aluminum 5083, about 900 °C for titanium Ti-6Al-4V.

  3. Blow in gas. Argon (an inert gas that keeps hot metal from reacting with air) flows in above the sheet at low pressure, typically about 10–30 bar.

  4. Let it stretch slowly. The sheet bulges like a soap bubble while the air below escapes through vents. Pressure rises gradually, so the metal stretches slowly, over minutes to hours, without tearing. Its tiny grains (the crystals that make up a metal) slide past each other, allowing stretches of several hundred percent.

  5. Fill the die, then open. The sheet meets the cavity walls and reaches the corners last, so the corners end up thinnest. The press opens, the hot part is lifted out, and its flange (the clamped rim) is trimmed off.

Key facts

Materials
Fine-grained superplastic alloys: titanium Ti-6Al-4V, aluminum 5083 and some aluminum-lithium alloys, some stainless steels
Typical parts
Aircraft doors, access panels and ducts, low-volume car body panels, hollow stiffened structures
Part size
From small brackets to panels a few meters long
Precision
Close to the die shape, typically a few tenths of a millimeter on the die side, with almost no springback (elastic bounce-back)
Surface finish
Smooth on the die side; titanium needs cleaning to remove a hard, oxygen-rich surface skin
Batch size it suits
Small to medium series: hundreds to a few thousand parts a year
Tooling and machine cost
One die only, in heat-resistant steel or ceramic, cheaper than matched stamping dies; the heated press is a large investment
Speed
Slow: roughly 15 minutes to a few hours per part, faster for aluminum than for titanium

Strengths and limits

Strengths

  • Deep, complex shapes in one piece, replacing assemblies of many parts
  • Only one die needed, so tooling costs less
  • Almost no springback, so shapes are accurate
  • With diffusion bonding (sheets fused under heat and pressure), makes hollow stiffened structures

Limits

  • Slow cycles: minutes to hours per part
  • Needs special fine-grained, more expensive alloys
  • Uneven thickness: corners and deep pockets thin out
  • Hot, energy-hungry process; titanium needs protective gas and surface cleaning

Where it's used

  • Aircraft structuresTitanium and aluminum doors, access panels and ducts
  • Jet enginesHollow titanium fan blades, made by combining SPF with diffusion bonding
  • AutomotiveAluminum body panels for low-volume sports and luxury cars
  • ArchitectureCurved aluminum facade and cladding panels

How to recognize it

  • Deep, smooth, soft-edged shapes made from one sheet, with no welds or seams.
  • One crisp, smooth side (the die side); the other side shows softer, rounded details.
  • Thickness that varies: thinner in corners and deep pockets, visible on a cut edge.
  • Draws deeper than an ordinary press could manage, always with generous radii.

Compare with

Stamping and deep drawing4.2cold, fast and with two matched dies, but shapes must be shallower and the dies cost more.Hydroforming4.5also fluid pressure against one die, but cold, with water or oil at far higher pressure.Thermoforming2.4the plastic cousin: a heated plastic sheet pulled onto a mold by vacuum or air pressure.

Watch it

superformusa · The core method: gas blows the hot sheet into a female die cavity

superformusa · A variant: the sheet is first blown into a bubble, then shaped over a male tool

superformuk · Real car body panels coming out of production

David Kirkham · Shop-floor footage of a formed part leaving the hot press

See real photos

Remember

  • Superplastic alloys stretch several hundred percent when hot and pulled slowly.
  • Gas pressure pushes the sheet into one single-sided die, so tooling stays simple.
  • Ideal for deep, complex one-piece panels; the price is slow cycles and thin corners.

More in Sheet and tube forming

All 100 processes
4.1Sheet metal bendingA press brake folds sheet along straight linesOpen the lesson4.2ShortStamping and deep drawingMatched dies cut and press sheet into shape, often in a secondOpen the lesson4.3Metal spinningA roller presses a spinning disc over a formOpen the lesson4.4Flow formingRollers stretch a spinning tube thinner and longer over a mandrelOpen the lesson4.5HydroformingFluid pressure pushes tube or sheet into a dieOpen the lesson4.6Incremental sheet formingA round tool traces contours into clamped sheet, with no dieOpen the lesson4.8Electromagnetic formingA magnetic pulse throws metal onto a fitting, without contactOpen the lesson4.9Explosive formingAn underwater blast pushes sheet into one dieOpen the lesson4.10Laser peen formingLaser shots stretch one face so a plate curvesOpen the lesson

Try it

Put AI to work in your CAD.

Model parts, generate drawings and automate the repetitive work inside your CAD software.

Download (Free)Book a demo