Ejection Force Calculator
Determine the force required to eject the part from the mold based on the lateral surface area, draft angle, surface roughness, and ejection temperature. Underestimating ejection force risks deformation or damage to the part.
Input Parameters
Results
Fill in the data and click Calculate
ARGUS automatically designs the ejection system based on part geometry and material
Ejection force depends on many factors — ARGUS integrates part geometry, material properties, and mold parameters into a single context.
How do we calculate ejection force?
Ejection force is the force needed to detach the part from the core or cavity walls after the material has solidified. The part adheres to the mold due to thermal shrinkage, which clamps the material onto cores, and friction between the part surface and the mold surface.
The calculator accounts for static friction force between the part and the mold, dependent on contact area, draft angle, roughness, and ejection temperature.
Fej — ejection force [N]
A — lateral surface area of part [cm²]
μ — friction coefficient (function of angle and roughness)
pshrink — shrinkage pressure [bar]
fT — temperature factor
The draft angle has a decisive influence on ejection force. The standard minimum is 0.5–1° per side, recommended 1–3°. For textured surfaces, the required angle is 1° per 0.025 mm of texture depth. Lack of draft angle leads to scratches, deformation, or cracking of the part during ejection.
Ejection system design
Ejection force determines the number, size, and placement of ejector pins. Insufficient ejector pin contact area causes deformation or puncturing of the part.
1.0° angle — standard for smooth surfaces
2.0° angle — comfortable ejection, recommended
3.0°+ angle — texture, deep cores
Ejection temperature affects the stiffness of the material — the lower the temperature, the stiffer the part and the lower the risk of deformation, but friction is higher. Optimal ejection temperature is a compromise between part rigidity and cooling time. Typically 10–30°C below the heat deflection temperature (HDT).
Ejection problems
Most common issues: ejector pin marks (insufficient contact area), scratches (no draft angle), cracking (ejection temperature too low, brittle material). Solutions: increase number of ejector pins, use ejector sleeve, air-assisted ejection, optimize cooling time.
ARGUS automatically designs the ejection system based on geometry and material
See it for yourself — book a presentation and discover how ARGUS integrates force calculations with the full mold context.