Metal spinning: turning a plate into a shape

Metal spinning is the mechanical sibling of forging. Instead of hammering the metal into shape, you rotate a round plate at high speed on a lathe and slowly press it down over a shape — a mandrel — with a hand-held pressure tool. The result is a round, seamless workpiece shaped in minutes instead of hours. Metal printer is an independent speciality under metal worker training precisely because the technique requires its own experience and its own tools.

§How the case is recorded and what happens next

A trimmed round plate is clamped between the mandrel and a backing (pressure disc) in the spindle so the plate and mandrel rotate together. With a pressing stick or a roller on a long lever arm the presser gradually feeds the metal over the mandrel's shape working from the outside inward in several passes. The metal flows over the form becomes longer radially and finally takes the mandrel's shape precisely. A lubricant such as soap or wax reduces friction and protects the surface.

§Tools and setup

• 01Mandrel (form): turned from hard wood, plastic or steel — determines the workpiece's shape
• 02Pinol with pressure disc: clamps the plate against the spindle
• 03Printing stake/spoon and rollers: press the metal over the mandrel
• 04Installation pivot (support point): provides the lever with support
• 05Lubricant: soap, wax or special paste against friction and heat

§Materials and items

The metals that press best are the tough malleable: aluminium copper brass and soft or stainless steel. For harder materials like stainless steel stronger machines and often pressing tools in solid brass are used. Typical products are bowls pots lamp shades funnels gas bottles dome lids and — classically — the bells of brass wind instruments. Because the object is seamless it can withstand high internal or external pressure which is exploited for pressure vessels and bottles.

§Hand and CNC printing

Traditional hand pressing is controlled entirely by pressman's experience and force over lever. In modern production same process is performed on CNC-controlled press bench where roll tool is guided by programmed paths — faster and uniform but same basic principle. Related variants are flow forming (shear forming/flow forming) where material thickness is deliberately reduced while metal flows out over mandrel

Advantages of metal printing

• 01Lave værktøjsomkostninger sammenlignet med dybtrækning og stansning
• 02Seamless items that can withstand pressure
• 03Small material waste
• 04Suitable for both single pieces, prototypes and series.

“Spinning is a drive set in rotation — same metal force, just controlled by the mandrel.”