Aluminum Die-Cast 5-Star Chair Base Custom Parts Case Study

Project Summary
The customer’s high-end office chair originally adopted glass fiber reinforced nylon 5-star base, which suffered creep deformation under heavy load and high fracture risk after long service. Common die-cast aluminum chair bases on the market had poorly designed wall thickness, stress concentration at arm roots, easy cracking during impact test, rough appearance and inconsistent dimensions, causing caster jamming. We adopted A380 die-cast aluminum alloy, optimized internal reinforcing ribs on five arms with integrated die-casting, matched with CNC machining for central hole & end mounting holes, sandblasting and passivation. The finished part balances lightweight, high structural strength and good appearance, passes BIFMA office chair load impact test with stable mass delivery.


Core Pain Points

1.Nylon 5-star bases creep under long-term load, deform gradually and break easily in fatigue test, bringing safety risks for premium office chairs

2.Standard aluminum die-cast bases lack reinforcing ribs at arm roots, stress concentration leads to fracture during impact test

3.Asymmetric shrinkage of five arms causes uneven height of leg ends, casters jam and chair slides unsmoothly

4.Many casting pores create pinholes after painting, poor appearance and downgrade furniture quality


Material Selection

A380 high-pressure die-cast aluminum alloy has excellent fluidity for integrated forming of large-size multi-branch 5-star structure. It is stronger than nylon with outstanding creep & impact resistance and anti-aging property. Good as-cast surface quality supports sandblasting or painting, balancing load capacity and lightweight.

Structure & Mold Optimization

1.Radial reinforcing ribs inside five arms plus thickened transition fillets at arm roots distribute stress and avoid impact fracture
2.Symbalanced gating system enables synchronized filling of five arms and uniform shrinkage, ensuring coplanar leg ends and smooth caster movement
3.Overflow & vent slots at ribs and corners reduce air entrapment and pores, improving cosmetic yield
4.Uniform CNC machining allowance, single-clamping machining for central bore and five end holes to guarantee positional accuracy