Lampshades are very common products in life. The materials selected for PC lampshades are basically light-diffusing PC materials/PMMA materials. We can make both materials. The following is the production process of lampshades

1. Demand analysis and digital design

Optical performance modeling

Light simulation: Use LightTools or Zemax OpticStudio to build a light path model to ensure that the light transmittance of the lampshade is ≥92% (PC material characteristics) and avoid glare (UGR＜19);

Structural verification: Use ANSYS topology to optimize the mold wall thickness (conventional 1.5-3mm) to balance lightweight and impact resistance (need to withstand 3kg falling ball impact).

Mold 3D design

Parting strategy: Use asymmetric parting lines for complex surfaces (such as Fresnel patterns), combined with 3D slider linkage mechanism (angle tolerance ±0.01°);

Conformal cooling: Metal 3D printing titanium alloy water channel (diameter 1.2-2mm) to ensure that the mold temperature fluctuation is ≤±1.5℃ to prevent PC material stress whitening.

2. Precision machining and surface treatment

Core technologies:

Cavity milling, five-axis ultra-precision machine tools (GF Machining Solutions), surface roughness Ra≤0.02μm

Microstructure etching, femtosecond laser + nanoimprint composite process, Fresnel depth 0.05mm±0.003mm

Electrode machining, graphite electrode EDM (discharge gap 0.03mm), edge R angle ≤0.1mm

Surface strengthening treatment:

Optical grade polishing: multi-level polishing with diamond paste (from W40 to W0.5), combined with magnetorheological polishing (MRF) to eliminate sub-surface damage;

Anti-stick coating: Diamond-like carbon (DLC) coating (thickness 2-3μm), reducing demolding force to <5kN, extending mold life to 800,000 molds

3. Trial mold verification and mass production optimization

Injection molding process window

Temperature control: barrel temperature 280-310℃ (PC melt index 18g/10min), mold temperature 90-110℃ (to prevent cold material marks);

Pressure curve: three-stage pressure holding (60MPa→45MPa→30MPa), compensation shrinkage rate 0.6-0.8%.

Defect closed-loop correction:

Weld line development, unreasonable gate position leads to the intersection of multiple streams, adjust the hot runner valve needle timing (error ±5ms)

Light spot distortion, mold microstructure collapse or uneven polishing, local repair welding + ion beam shaping (correction amount 0.005mm)

Stress cracking, insufficient demoulding slope (<1°) or too fast ejection speed, increase the number of ejector pins (1 for every 100cm²)

4. Key points of injection mold production:

Optical performance and structural design

Light transmittance and light path control

Surface microstructure: Nano-scale Fresnel lens design (depth accuracy ±0.003mm), achieved by laser etching or electroplating process, so that the light scattering angle ≤15°, avoid glare (UGR value needs to be <16);

Wall thickness uniformity: Use topology optimization algorithm (ANSYS Discovery) to balance light transmittance and intensity, wall thickness 1.2-2.5mm, tolerance control ±0.05mm. Parting line and demoulding strategy

Asymmetric parting: 3D slider + hydraulic core pulling linkage is used for special-shaped curved surfaces (such as petal-shaped lampshades), and the parting line offset angle is ≤0.5° to ensure no flash;

Demolding slope: The slope of the optical surface area is ≥1.5°, and the non-optical surface is ≥0.8°. The ejection system uses silicon nitride ceramic ejector pins (friction coefficient <0.1).

Cooperative optimization of materials and processes

Mold steel selection

High polished steel: S136 SUPREME (HRC 52-54) or German Gritz 1.2085 ESR (mirror polished to Ra 0.008μm) are preferred;

Corrosion-resistant treatment: The surface is coated with diamond-like carbon (DLC) coating (thickness 2-3μm) to resist the acidic gas generated by high-temperature decomposition of PC.