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# Ejection System Design for Aluminum Casting Molds: Ejector Pin, Plate & Force Calculation Unreasonable ejection system causes casting bending, surface draggi

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  • Release time: 2026-09-29

Ejection System Design for Aluminum Casting Molds: Ejector Pin, Plate & Force Calculation

Unreasonable ejection system causes casting bending, surface dragging marks and stuck parts, raising rejection rate by 31%. This chapter covers ejector layout, ejector pin specification, ejection force calculation and maintenance standards for LPDC and gravity aluminum casting molds.

Total ejection force calculated by casting projected area × mold sticking coefficient. Coefficient set to 0.28–0.35 MPa for A356 aluminum alloy after nitrided mold surface.

Multi-point symmetric ejector layout to avoid unbalanced force. Ejector pins arranged around bosses, ribs and thick wall regions; spacing between ejector pins 40–70 mm.

Ejector pin diameter selection Φ6–Φ12 mm for most automotive aluminum castings. Small diameter pins bend easily; oversized pins occupy too much cooling channel space.

Ejector pin surface nitriding layer 0.07–0.10 mm, surface hardness Hv950–1050 to resist wear and aluminum adhesion. Ejector pin tip Ra0.8 μm polishing requirement.

Ejector plate guided by 4–8 guide posts to ensure parallel movement. Guide post clearance controlled at 0.015–0.025 mm to prevent ejector pin jamming.

Ejector stroke reserved 8–12 mm more than casting demolding travel, with travel limit switch for safety protection.

Ejector sleeve used for boss hole demolding. Sleeve inner hole tolerance ±0.012 mm, matched with core pin clearance 0.01–0.02 mm.

Draft angle: external surface draft 1.2°–2.0°, internal rib draft 2.0°–3.0°. Draft angle below 1° easily creates drag marks and part sticking.

Anti-wear plate installed on ejector plate contact surface, reducing friction wear by 40% and extending ejection system service life.

Ejector return adopts spring return plus mechanical reset pin for double insurance, preventing collision during mold closing.

Ejector pin inspection every 2500 cycles: check bending, wear, soldering and pin length variation; replace pins when wear exceeds 0.03 mm.

FAQ

Q1: How to calculate ejection force for A356 aluminum casting? A1: Ejection force = casting projected area × sticking coefficient 0.28–0.35 MPa. Q2: What draft angle is required for internal ribs of aluminum casting? A2: Internal rib draft angle recommended 2.0°–3.0° to avoid drag marks. Q3: What maintenance check frequency for ejector pins? A3: Inspect ejector pins every 2500 casting cycles for wear and deformation.

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