Reverse Extrusion

Reverse Extrusion is an extrusion process in which the material flows in the opposite direction to the movement of the punch during forming. The punch penetrates the raw material and displaces the material, which flows back along the punch in the opposite direction.

This method is particularly suitable for producing cavities and cup- or sleeve-shaped geometries. Reverse flow forming is therefore suitable for components where hollow areas are to be created during the forming process itself.

In cold extrusion, the forming takes place without first heating the material to forming temperature. Reverse extrusion can be used as a single forming operation or as part of a multi-stage forming process.

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Reverse Extrusion in cold forming
Reverse Extrusion: Questions and answers

Reverse Extrusion in cold forming

In reverse flow forming, the punch penetrates the raw material. The displaced material flows against the direction of the punch’s movement into the space between the punch and the die. This allows a hollow section of the component with a defined wall thickness to be formed.

The process enables the production of various internal and external geometries and is particularly suitable for components such as sleeves, bushings or other parts with hollow sections. The achievable geometry is determined, amongst other factors, by the material, initial dimensions, degree of forming, and the geometry of the punch and die.

A key advantage over machining methods for producing hollow geometries lies in material utilisation. The hollow cavity is not created by removing material. Instead, the existing material is specifically displaced into the required component areas. Consequently, reverse flow forming can enable material-efficient and cost-effective production, particularly for high production volumes.

For more complex cold-formed parts, reverse flow forming is frequently combined with further forming operations. For example, different diameters, shoulders, flanges, steps or other functional geometries can be produced step by step within a multi-stage forming sequence.

Reverse Extrusion: Questions and answers

What is Reverse Extrusion?

Reverse extrusion is an extrusion process in which the material flows in the opposite direction to the movement of the punch. The punch penetrates the raw material and forces the material back along the punch.
What geometries can be produced using Reverse Extrusion?

Reverse Extrusion is particularly suitable for producing hollow geometries. These include, for example, cup- or sleeve-shaped component sections. The internal and external geometries that can be achieved depend, amongst other things, on the material, the degree of forming and the tool design.
How is the cavity formed during Reverse Extrusion?

The punch penetrates the material, displacing it in the process. The displaced material flows against the direction of the punch’s movement through the space between the punch and the die. In this way, the cavity is created by material displacement rather than by machining.
What are the advantages of Reverse Extrusion?

The process enables the material-efficient production of hollow geometries and can therefore reduce or eliminate machining steps. This can result in advantages in terms of material usage, production time and cost-effectiveness, particularly for high production volumes.
What is the difference between Forward and Reverse Extrusion?

The main difference lies in the direction of material flow relative to the punch movement. In Forward Extrusion, the material essentially flows in the direction of the punch’s movement. In Reverse Extrusion, by contrast, it flows against the punch’s movement. Both processes can be combined within a multi-stage cold forming process.

Reverse Extrusion

Reverse Extrusion in cold forming

Reverse Extrusion: Questions and answers

What is Reverse Extrusion?

What geometries can be produced using Reverse Extrusion?

How is the cavity formed during Reverse Extrusion?

What are the advantages of Reverse Extrusion?

What is the difference between Forward and Reverse Extrusion?