📤Demold & Ejection Design
Rubber hugs the core after demolding because of shrinkage grip. Estimate the demolding force and the ejector-pin area needed to push the part off without marking it.
Demolding force & ejector sizing
E ≈ 10(0.0235·HA − 0.64)
HA = Shore A hardness
p = E · Shrink / 100
F = p · A · µ / 10
A = lateral contact area (cm²) · µ = friction coefficient · result in kN
Units & validation
Editable: hardness 10–100 A · shrinkage 0.1–10 %
A = 0.1–5000 cm² · µ = 0.1–2.5 · pin Ø 1–40 mm
✓ Result
Grip pressure p
Demolding force F
Required pin area
Recommended pins (Ø d)
Recommended draft angle
Grip pressure p comes from shrinkage tightening the part around the core; use a higher µ (≈1.0–1.5) for rough core finish and dry surfaces, lower for polished/lubricated cavities. For undercuts, add the force to deform the lip over the undercut.