Enter the billet area, extruded product area, and the extrusion constant into the calculator to determine the extrusion force.

Extrusion Force Calculator

Enter any 3 values to calculate the missing variable

Extrusion Force Formula

The following equation is used to calculate the Extrusion Force in a simplified (idealized) direct-extrusion model that relates force to area reduction.

EF = A0 * k * ln ( A0/Af)
  • Where EF is the extrusion force (lbf)
  • A0 is the billet area (in^2)
  • Af is the extruded product area (in^2)
  • k is an effective extrusion “constant” with stress units (lbf/in^2), typically determined empirically for the material/process conditions

To calculate the extrusion force, multiply the billet area by the extrusion constant, then multiply by the natural log of the ratio of the billet area to the extruded product area (A0 > Af so the logarithm is positive).

What is an Extrusion Force?

Definition:

An Extrusion Force measures the axial force required to push a billet/material through a die opening (commonly in ram/direct metal extrusion). The force is measured in pounds-force (lbf) or newtons (N). In general, higher force means the material offers more resistance to deformation/flow through the die.

How to Calculate Extrusion Force?

Example Problem:

The following example outlines the steps and information needed to calculate the Extrusion Force.

First, determine the billet area. In this example, the billet area is measured to be 12 in^2.

Next, determine the extruded product area. The extruded product area in this problem is 8 in^2.

Next, assume the extrusion constant is 50 lbf/in^2.

Finally, calculate the extrusion force using the formula above;

EF = A0 * k * ln ( A0/Af)

EF = 12 * 50 * ln ( 12/8)

EF = 243.27 lbf

FAQ

What factors can affect the extrusion force required during the extrusion process?

The extrusion force can be affected by several factors including the material’s flow stress (or resistance to deformation), the temperature at which extrusion is performed, the extrusion speed/strain rate, the die angle and bearing length, and friction/lubrication. Higher flow stress, less favorable die geometry, and higher friction generally increase the required force.

How does the extrusion constant (k) vary between different materials?

In this simplified model, the “extrusion constant” (k) is an effective stress-like parameter. For metal billet extrusion, it is commonly related to the material’s (mean) flow stress at the extrusion temperature and can also reflect process effects such as friction and die geometry. It should be obtained from experiments, tooling/process references, or validated process models for the specific material and conditions.

Can the extrusion force formula be used for materials other than plastics, such as metals?

This logarithmic area-reduction formula is most commonly used as an idealized approximation for ductile solid-billet extrusion (often metals). It is not generally applicable to polymer screw/die extrusion, where pressure/force is typically governed by melt rheology (viscosity), flow rate, temperature, and detailed die geometry rather than a simple ln(A0/Af) reduction model.