Comprehensive Analysis of Advanced Technology for Single-Use Lunch Box Injection Moulds
1. Innovative Mould Structure System
1.1 Multi-layer Rotating Stack Mould Technology
Adopts a four-layer rotating stack mould design, with each layer containing 4-6 cavities. Synchronous opening and closing are achieved through a central rotating shaft. The rotating mechanism uses planetary gear transmission with a precision grade of DIN Class 5, allowing each mould layer to rotate 180° independently for product ejection. The total stack mould thickness is controlled at 600-800mm, increasing production capacity by 200-300% compared to traditional moulds. Each layer is equipped with an independent hot runner system, employing a split hot runner plate design, with temperature variation between layers controlled within ±1.5°C.
1.2 Ultra-Thin Wall Rapid Cooling System
For the thin-wall structure of lunch boxes (0.4-0.6mm), micro-channel cooling technology has been developed. Cooling channels have a diameter of Φ4-6mm, positioned 3-5mm from the cavity surface, and are formed by laser welding 316L stainless steel tubes. The channel network features a three-dimensional mesh structure, forming 5mm×5mm cooling grid units. In reinforcement rib areas, miniature cooling copper tubes with diameters of Φ2-3mm are installed using hot-press embedding technology. Cooling water flow rate is 15-20L/min, pressure 0.4-0.6MPa, and cooling time 2.5-3.5 seconds.
2. Hot Runner System Innovations
2.1 Multi-Point Sequential Control Hot Runner
Employs a 16-point needle valve sequential hot runner, with each cavity configured with 2-4 gates, each with a diameter of Φ1.2-1.8mm. Needle valves are driven by servo motors, with opening time accuracy of ±0.01 seconds and stroke consistency of ±0.02mm. The hot runner system is divided into 4 independent temperature control zones, each equipped with a PID intelligent temperature control module, providing temperature control accuracy of ±0.3°C. Runners use a stepped variable diameter design, with the main runner diameter gradually reducing from Φ12mm to Φ6mm, and branch runner diameters of Φ5-8mm, reducing pressure loss by 30-40%.
2.2 Low-Temperature Molding Hot Runner
For bio-based materials such as PLA and PBS, a low-temperature hot runner system has been developed, operating at 120-160°C. It uses PEEK insulation materials and ceramic heating elements, reducing heat loss by 40-50%. Runner surfaces receive special coating treatment, with a friction coefficient ≤0.1, preventing degradation of bio-based materials. Equipped with melt temperature monitoring sensors, it adjusts temperatures in various zones in real-time, controlling temperature differences within ±2°C.
3. Ejection System Innovations
3.1 Pneumatic-Hydraulic Hybrid Ejection System
Adopts a pneumatic pilot + hydraulic main ejection composite structure. First, compressed air at 0.3-0.5MPa forms an air film on the parting surface, separating the product from the cavity by 0.1-0.2mm. Then, the hydraulic ejection mechanism ejects the product at a speed of 8-12mm/s. Ejector pins are arranged radially, with auxiliary ejection blocks placed at the edges of the lunch box and reinforcement rib positions. Ejection stroke is 20-30mm, with ejection time of 0.5-0.8 seconds.
3.2 Anti-Stick Surface Treatment
Cavity surfaces employ a three-layer composite treatment process:
Base treatment: Mirror polishing to Ra 0.05-0.1μm
Micro-etching treatment: Formation of regular 5-10μm凹凸 textures
Nano-coating: DLC (Diamond-Like Carbon) coating, thickness 2-3μm, hardness 3000-3500HV
Draft angles: 0.5°-1°, enlarged to 1.5°-2° at corners.
4. Material Compatibility Design
4.1 Multi-Material Compatible Runner
The mould runner system is compatible with four materials: PP, PS, PLA, and PBS. Rapid switching is achieved by replacing the manifold and gate inserts. To accommodate the flow differences of various materials, runner dimensions are adjustable: PP material runners are enlarged by 10-15%, while PLA material runners are reduced by 5-10%. A material identification system is included to automatically adjust process parameters.
4.2 Special Design for High-Filler Materials
For calcium carbonate-filled materials (filler content 20-40%), the following proprietary designs are used:
Runner surface hardness: 60-63 HRC
Gate angle: 30°-45° (to reduce shear)
Venting depth: 0.03-0.05mm
Wear-resistant coating: CrN coating, thickness 5-8μm
5. Precision Manufacturing Technology
5.1 Ultra-Precision Cavity Machining
Utilizes five-axis high-speed milling, with spindle speeds of 20,000-24,000 rpm and feed rates of 10,000-15,000 mm/min. Thin-wall areas are machined layer by layer using micro-diameter milling cutters (Φ0.3-0.8mm), with a cutting depth of 0.02-0.05mm per layer. Post-machining cavity dimensional accuracy: ±0.01mm, positional accuracy: ±0.005mm, thin-wall thickness tolerance: ±0.02mm.
5.2 Mould Inspection Technology
A 3D white light scanner inspects cavity profiles, with a measurement point density of 200 points/cm² and a comparison accuracy of 0.005mm against the design model. A laser confocal microscope measures surface roughness, with a measurement range of Ra 0.01-10μm. Cooling channels undergo endoscope inspection to ensure no blockages or leaks.
6. Production Efficiency Optimization
6.1 Ultra-Short Cycle Molding Process
Injection time: 0.8-1.2 seconds
Holding time: 1.0-1.5 seconds
Cooling time: 2.5-3.5 seconds
Mold opening/closing time: 1.0-1.5 seconds
Ejection time: 0.5-0.8 seconds
Total cycle: 5.8-8.5 seconds
6.2 Quick Mold Change System
The mould is equipped with an HSK quick mold change interface, enabling mold change time ≤3 minutes, including:
Hydraulic quick clamping device
Plug-and-play water/electrical connectors
Automatic centering and positioning system
RFID mould identification system
7. Mould Technical Specifications
7.1 Basic Specifications
Number of cavities: 16-24 cavities (four-layer stack mould)
Mould dimensions: 700×700×650mm
Injection machine tonnage: 300-600 tons
Clamping force: 200-400 tons
Shot weight: 300-600g
Mould weight: 4-6 tons
Heating power: 20-30kW
7.2 Performance Indicators
Daily output: 120,000-200,000 pieces (24 hours)
Material utilization rate: ≥96%
Product qualification rate: ≥99.2%
Energy consumption index: 0.8-1.2 kWh/kg
Mould life: 2.5-3.5 million cycles
8. Quality Control System
8.1 Online Inspection System
Laser thickness gauge: Real-time wall thickness monitoring, accuracy ±0.005mm
Infrared thermal imager: Temperature distribution monitoring, accuracy ±0.5°C
Weight sorter: Weight deviation detection, accuracy ±0.01g
Vision inspection system: Surface defect detection, resolution 0.02mm
8.2 Product Testing Standards
Sealing performance: ≥0.05MPa, no leakage for 30 minutes
Stacking strength: ≥10 layers without deformation
Drop test: 1.2m height, no breakage after 3 drops
Microwave test: 800W, no deformation after 3 minutes
Oil resistance test: 95°C oil, no penetration after 2 hours
9. Technological Innovation Applications
9.1 Functional Integration Technology
Leak-proof design: Integrated silicone sealing groove
Breathable design: Micro-porous ventilation structure
Insulation design: Air interlayer structure
Easy-tear design: Pre-set tear lines
9.2 Environmental Technologies
Lightweight design: 20-30% weight reduction
Mono-material: Facilitates recycling
Compostable certification: Compliant with EN 13432 standard
Water-saving design: Cooling water recycling rate ≥95%
10. Economic Benefit Analysis
10.1 Production Costs
Mould investment: 250,000-450,000 RMB
Material cost per piece: 0.05-0.12 RMB
Energy cost per piece: 0.01-0.02 RMB
Labor cost per piece: 0.005-0.01 RMB
Comprehensive cost per piece: 0.08-0.18 RMB
10.2 Return on Investment
Daily output value of 24-cavity mould: 10,000-18,000 RMB
Monthly output: 300,000-540,000 pieces
Investment payback period: 4-8 months
Annual return on investment: 30-45%
11. Maintenance System
11.1 Daily Maintenance
Every 2 hours: Clean parting surfaces
Every 4 hours: Check hot runner temperature
Per shift: Lubricate moving parts
Daily: Check cooling system
11.2 Preventive Maintenance
Every 50,000 cycles: Check cavity dimensions
Every 100,000 cycles: Inspect surface roughness
Every 200,000 cycles: Replace seals
Every 500,000 cycles: Comprehensive overhaul
12. Technology Development Trends
12.1 High Efficiency
Cycle time reduced to 4-6 seconds
Number of cavities increased to 32-48
Mold change time reduced to under 1 minute
12.2 Intelligence
12.3 Green Technology
100% compatibility with bio-based materials
Zero-emission cooling system
Energy recovery and utilization
Conclusion: Modern single-use lunch box injection moulds achieve high-efficiency, low-cost, and high-quality mass production through technological innovations such as multi-layer stack moulds, ultra-thin wall molding, and rapid cooling. The future direction will continue toward higher speed, more intelligent control, and more environmentally friendly materials, providing sustainable technological solutions for the food packaging industry.
