Electroforming

How it works

1. 1

   Make the mandrel. The mandrel (the master shape the metal grows on) is machined, molded, 3D printed or etched. Its surface is the negative of the one you want.

2. 2

   Make its surface conductive. Plastic, wax or glass mandrels get a very thin conductive coat, such as silver paint or graphite. Metal mandrels get a release layer instead, so the copy can let go later.

3. 3

   Immerse and connect. The mandrel goes into an electrolyte (a bath of dissolved metal salts), facing an anode (the positive electrode, a nickel or copper plate). A DC power supply makes the mandrel the cathode (the negative electrode).

4. 4

   Grow the metal. The current pulls metal ions (electrically charged atoms) onto the mandrel, where they turn into solid metal. The anode slowly dissolves and refills the bath. The layer typically thickens by tens of microns per hour, so a part takes hours to days.

5. 5

   Separate the copy. The shell is peeled or lifted off, or the mandrel is melted or dissolved away. The copy is trimmed and finished; a reusable mandrel goes back in for the next one.

Key facts

Materials

Mostly nickel and copper, also gold, silver and iron; mandrels of metal, glass, silicon, plastic or wax

Typical parts

Thin shells, foils, fine meshes, seamless hollow parts, finely textured molds

Part size

From micro-parts under 1 mm to shells tens of centimeters across; walls from a few microns to several millimeters

Precision

Copies mandrel detail below 1 µm (a thousandth of a millimeter); wall thickness is less even, thicker on edges and corners

Surface finish

Inner side as smooth as the mandrel, mirror-like on a polished one; outer side matte and less defined

Batch size it suits

One-offs to medium series; one mandrel can make many copies

Tooling and machine cost

Low to moderate: hundreds of dollars for a hobby tank, typically tens of thousands and up for an industrial line; the long time in the bath is the main cost

Speed

Slow: typically tens of microns per hour, so a 1 mm wall takes about a day or more

Strengths and limits

Where it's used

• Music and mediaVinyl record stampers, CD and DVD stampers
• Consumer productsElectric shaver foils, fine filters and sieves
• Printing and electronicsInkjet nozzle plates, rotary screen-printing screens, micro-molds
• Space and opticsX-ray telescope mirror shells, reflectors, waveguides
• AerospaceThin-wall nozzles, cooling jackets, bellows
• Jewelry and artLight hollow gold and silver pieces, metal-coated leaves

How to recognize it

• A thin metal part that copies a texture with startling sharpness, like the tiny holes of a shaver foil.
• A light, hollow piece with no seam, whose inside mirrors the shape of a model.
• Edges and corners slightly thicker or rounder than flat areas, from extra metal build-up.
• A leaf or shell turned into metal with every vein and ridge still visible.

Compare with

Watch it

What is Nickel electroforming?

Winovus · How nickel grows on a mandrel, then is separated

Vinyl Record Plating Process Explained

Well Made Music · How a record master becomes nickel stampers

Electroforming

Guild's Garage · A small workshop setup: conductive paint, bath, power supply

Electroforming Leaves: Step By Step Process

Electroforming Artist · A real leaf painted, plated and turned into copper

See real photos

• Wikipedia: Electroforming — principle, mandrels and uses; mostly text, few photos
• Wikimedia Commons photo search