一, Mold design: precision structure lays the foundation of quality
1. Selection of mold materials
High gloss molds need to withstand high temperatures of 80 ℃ -130 ℃ and rapid cooling cycles below 40 ℃, with extremely high requirements for material thermal fatigue strength. The mainstream solutions in the industry include:
S136H (Sweden): After rough machining, quenched to HRC52, suitable for complex structural components;
CEANA1 (Japan): Comes with HRC42 hardness, does not require quenching treatment, making it easy for subsequent processing;
CPM40/GEST80 (Germany): High purity steel suitable for ultra-thin wall products.
Taking the middle frame mold of an international brand smartphone as an example, using S136H steel combined with vacuum heat treatment technology, the mold's lifespan exceeded 1 million times, and the surface roughness reached Ra ≤ 0.01 μ m, directly supporting the production grade mirror effect.
2. Optimization of waterway system
The rapid cooling and rapid heating process requires the mold waterway to achieve a "second level response":
Aperture design: Adopting a 5-6mm waterway and a 1/8-inch water nozzle to ensure uniform water flow;
Layout: Circular products use circular waterways, while irregular products use three-dimensional conformal waterways to reduce thermal energy loss;
Sealing technology: Use an extended water pipe directly connected to the mold core instead of traditional sealing rings to avoid the risk of water leakage caused by high temperature aging.
A certain laptop A-shell mold has reduced the heating time from 45 seconds to 18 seconds, the cooling time from 32 seconds to 12 seconds, and the injection molding cycle by 65% by optimizing the waterway layout.
3. Innovation of hot runner system
In response to the challenge of welding line control, the industry has developed multi-level hot runner technology:
Independent airway control: Each hot nozzle is equipped with a sealing needle and solenoid valve, and timed injection of glue is achieved through a time relay;
Gate optimization: Adopting large-sized gates (diameter ≥ 3mm) with short runner design to reduce material degradation caused by shear heat.
After applying this technology to the mold of a smartwatch case, the number of fusion lines decreased by 90% and the surface glossiness increased by 40%, directly passing the strict appearance inspection standards of the brand.
二, Temperature control system: dynamic control achieves process breakthrough
1. Principle of rapid cooling and rapid heating technology
By quickly switching between steam/high-temperature water and cooling water, dynamic control of mold temperature can be achieved:
High temperature stage: Before injection, steam at 150 ℃ is introduced to raise the mold temperature to above 120 ℃, ensuring that the melt maintains a viscous flow state;
Low temperature stage: Inject 4 ℃ cooling water after holding pressure, causing the mold temperature to drop sharply below 60 ℃ and accelerating resin curing.
After applying this technology to a high-end TV frame mold, the surface shrinkage rate decreased from 0.8% to 0.2%, the amount of warping deformation decreased by 75%, and the yield rate increased to 99.2%.
2. Closed loop control system
Adopting a fully closed-loop temperature control scheme:
Sensor layout: PT100 temperature sensors are embedded in key positions such as mold cavity, hot runner, and waterway;
Control accuracy: The precision of the mold temperature machine reaches ± 0.3 ℃, and the steam/cooling water flow is adjusted in real-time with the help of PLC;
Data visualization: Display temperature curves through color charts to achieve dynamic optimization of process parameters.
A certain car control screen mold uses closed-loop control to control the surface temperature difference within ± 1 ℃, completely eliminating flow marks and silver wire defects.
三, Material selection: Performance matching supporting process implementation
1. High fluidity engineering plastics
The mainstream materials in the field of consumer electronics include:
ABS+PC alloy: Melt Flow Index (MFI) ≥ 30g/10min, impact resistance up to 20kJ/m ²;
PMMA: Light transmittance>92%, surface hardness up to 2H, suitable for the production of transparent parts;
ASA: Excellent weather resistance, no color change after 5 years of outdoor use, suitable for smart wearable devices.
The shell of a certain brand of tablet computer is made of high gloss ABS+PC material, combined with rapid cooling and heating process, with a surface glossiness of over 90GU, directly replacing traditional spraying process.
2. Additive technology
To solve the problem of yellowing caused by high-temperature processing, the industry has developed a specialized additive system:
Light stabilizer: absorbs ultraviolet rays to prevent material degradation;
Antioxidants: inhibit oxidation reactions and extend the service life of materials;
Lubricant: Reduce melt viscosity and improve mold filling performance.
The frame material of a certain mobile phone meets the strict requirements of the high-end market by adding 0.5% nano level light stabilizer to achieve a color difference Δ E ≤ 0.3 after high-temperature processing.
四, Process control: Fine management ensures stable quality
1. Injection parameter optimization
Adopting three-stage pressure control technology:
Filling stage: pressure ≥ 120MPa, ensure that the melt fills the mold cavity;
Pressure holding stage: pressure of 80-100MPa, compensating for material shrinkage;
Cooling stage: pressure of 20MPa to prevent product deformation.
A certain laptop shaft mold has improved the welding line strength to 35MPa through parameter optimization, exceeding the industry average by 20%.
2. Mold maintenance standards
Establish standardized maintenance procedures:
Daily cleaning: Use an ultrasonic cleaning machine to remove oil stains and debris from the surface of the mold;
Regular polishing: Diamond polishing paste is used for mirror polishing to maintain surface roughness Ra ≤ 0.02 μ m;
Rust prevention treatment: Apply specialized rust prevention oil to prevent the mold from rusting in humid environments.
A certain mold factory has extended the service life of molds to 1.2 million times and reduced single piece costs by 18% by implementing this standard.
五, Industry application cases and trend prospects
1. Typical application scenarios
Smartphone: A flagship model of a certain brand achieves seamless connection between the middle frame and glass back panel through high gloss seamless technology, enhancing the overall texture of the device;
Smart wearables: The case of a certain smartwatch adopts rapid cooling and heating technology, with a surface hardness of 3H and a 3-fold increase in scratch resistance;
Home appliances: A high-end refrigerator panel has won the IF Design Award for eliminating seam marks through this technology.
2. Technological development trends
Composite function integration: Combining LDS (Laser Direct Molding) technology, directly etching antenna lines on high gloss surfaces;
Intelligent production: Introducing AI algorithms to optimize process parameters in real-time, achieving "one machine, multiple modes" flexible production;
Green Manufacturing: Develop a formula for recyclable materials, combined with a closed-loop temperature control system, to reduce VOC emissions by 90%.
