Understanding Plastic Chair Mould Production

Plastic chair moulds are among the most technically demanding products in the injection mould industry. This article walks you through the complete production process.

Phase 1: Design and Engineering

Product Design Review

• Ergonomic assessment
• Structural analysis (FEA)
• Weight optimization
• Aesthetic refinement

Mould Design

• 3D mould design with CAD
• Mould flow analysis
• Cooling simulation
• Ejection system design

Phase 2: Material Preparation

Steel Selection

Common steels for chair moulds:

• P20: Cost-effective, good for moderate runs
• 718H: Pre-hardened, excellent polishability
• S136: Corrosion resistant, mirror finish capability

Steel Procurement and Inspection

• Verify steel certificates
• Check hardness
• Inspect for defects

Phase 3: Rough Machining

CNC Machining

• Remove bulk material
• Create basic geometry
• Leave 0.3-0.5mm for finish machining

Deep Hole Drilling

• Cooling channel drilling
• Ejector pin holes
• Guide pin holes

Phase 4: Heat Treatment

For Tool Steel

• Vacuum hardening
• Stress relief
• Dimensional stabilization

Phase 5: Finish Machining

High-Speed CNC

• Achieve final dimensions
• Surface finish preparation
• Tolerance: ±0.02mm typical

EDM (Electrical Discharge Machining)

• Complex geometries
• Fine details
• Textures

Phase 6: Surface Treatment

Polishing

• Progressive polishing grades
• Mirror finish for visible areas
• Texture application

Coating (Optional)

• Chrome plating for wear resistance
• Nitriding for hardness
• PVD coating for special applications

Phase 7: Assembly

Component Assembly

• Core and cavity fitting
• Slider and lifter installation
• Cooling system assembly
• Ejection system assembly

Hot Runner Installation

• Manifold mounting
• Nozzle alignment
• Wiring and temperature control

Phase 8: Trial and Optimization

First Trial (T1)

• Initial sampling
• Identify issues
• Measure dimensions

Optimization

• Adjust processing parameters
• Fine-tune cooling
• Modify if necessary

Final Trial (T2/T3)

• Confirm all specifications
• Production speed test
• Quality consistency check

Gas-Assist Technology for Chairs

Many modern chair moulds use gas-assist injection:

Benefits:

• Reduced material usage (15-30%)
• Lighter products
• Eliminated sink marks
• Shorter cycle times

Requirements:

• Specialized nozzle design
• Nitrogen supply system
• Modified process control

Quality Inspection

Dimensional Inspection

• CMM measurement
• Profile projection
• 3D scanning comparison

Functional Testing

• Mould opening/closing
• Ejection smoothness
• Cycle time verification

Conclusion

Chair mould production is a complex process requiring expertise at every stage. Understanding this process helps you better communicate with your mould manufacturer and ensure optimal results.