Comprehensive Process and Technical Advantages of Removing Flash and Burrs from Silicone Earplugs with Cryogenic Deflashing Machine
In the manufacturing of silicone earplugs, the delicate treatment of flash and burrs directly affects product wearing comfort and hygiene standards. Cryogenic deflashing technology, leveraging the composite process of low-temperature embrittlement and precise spraying, has become the core solution for silicone earplug surface finishing. This article details the standard process of removing flash from silicone earplugs using a Liquid nitrogen flash machine and analyzes the key roles and technical advantages of Sand blasting machine and small sand blasting machine in refined processing.
I. Pretreatment: Dual Preparation of Earplugs and Equipment
1. Initial Inspection and Fixing of Silicone Earplugs
Flash Positioning: Flash distribution is identified via a visual inspection system (precision ±0.01mm), commonly found at the junction of earplug stems and cavities, parting surfaces, and earplug tips. Record burr thickness (typically 0.05–0.2mm) and silicone hardness (Shore A 20–40).
Flexible Fixture Design: Medical-grade silicone fixtures produced by 3D printing are used to fix earplugs. Contoured grooves are designed for ergonomic surfaces to avoid deformation from stress concentration at low temperatures. Fixture surfaces undergo hydrophobic treatment to prevent silicone adhesion affecting demolding.
2. Parameter Setting for Liquid nitrogen flash machine
Cryogenic Embrittlement Threshold: Equipment temperature is adjusted to −160℃–−196℃ based on silicone properties, with a holding time of 8–12 minutes. This embrittles flash areas due to molecular chain contraction (hardness increases to Shore A 85+), while maintaining the soft elasticity of main earplugs (elongation ≥400%).
Spray Media Preparation: 0.08–0.15mm nylon sand (Shore D 70–75 hardness) is used, pre-dried at 120℃ for 4 hours to ensure no moisture residue, avoiding impact on silicone surface skin-friendliness.
II. Liquid Nitrogen Cryogenic Deflashing: Flash Embrittlement and Batch Removal
1. Gradient Cryogenic Embrittlement
Staged Cooling: After starting the Liquid nitrogen flash machine, earplugs are pre-cooled at −80℃ for 3 minutes, then gradually cooled to the target temperature to prevent internal stress from sudden temperature changes. Liquid nitrogen atomization particle diameter in the chamber is controlled at 30–60μm, with circulating airflow (wind speed 10m/s) ensuring uniform flash cooling and surface temperature difference ≤1.5℃.
Temperature Field Monitoring: Real-time monitoring via infrared thermography focuses on heat dissipation blind spots like earplug tips and grooves. Auxiliary nozzles are added if necessary to ensure consistent flash embrittlement.
2. Low-Pressure Sandblasting for Flash Removal
Kinetic Energy Matching: After freezing, the equipment drives nylon sand with 0.2–0.4MPa compressed air at 50–80m/s. "20° angled spraying" is used for thin flash below 0.1mm, while spiral spraying paths are applied to thick flash (>0.15mm), with single-pass removal ≤0.03mm to prevent surface damage (roughness controlled at Ra≤0.8μm).
Automated Trajectory: CNC-generated contoured spraying trajectories ensure no flash residue in delicate areas like ear canal-contacting surfaces and ventilation holes, protecting the acoustic structure of earplugs.
III. Sandblasting Finishing: Surface Quality Optimization
1. Coarse Sandblasting with Sand blasting machine
Batch Processing: For conventional silicone earplugs, a turntable-type Sand blasting machine is used. Earplugs are loaded with 0.15–0.25mm glass beads (roundness ≥98%) and sandblasted at 40rpm for 4 minutes to reduce surface roughness from Ra 3.2μm to 1.2μm.
Process Parameters: Sandblasting pressure 0.2MPa, spraying distance 10cm. The turntable angle is adjusted via servo motor for uniform sand exposure, avoiding over-blasting that could roughen the surface and affect wearing comfort.
2. Fine Trimming with small sand blasting machine
Local Micro-Processing: For high-precision products like noise-canceling or medical earplugs, a small sand blasting machine is used with 0.05mm corn starch sand. Under a 20x microscope, secondary sandblasting eliminates 0.01mm-level burrs on critical areas like ventilation holes and sealing lips, avoiding damage to acoustic structures.
Static Control: An ion air bar (wind speed 10m/s) is activated during sandblasting to prevent static adsorption of sand particles, ensuring earplug surface cleanliness meets medical or consumer product standards.
IV. Post-Processing and Quality Verification
1. Cleaning and Performance Recovery
Ultrasonic Cleaning: Earplugs are placed in an ultrasonic tank with medical-grade detergent (40kHz) for 3 minutes, then rinsed three times with deionized water. Medical-grade earplugs require additional pure water spraying (conductivity ≤1μS/cm).
Disinfection Treatment: After cleaning, ultraviolet disinfection (wavelength 254nm, irradiation for 15 minutes) or ethylene oxide sterilization is performed to ensure earplugs meet medical ISO 10993 standards or consumer product hygiene requirements.
2. Full-Dimension Inspection
Visual Inspection: Under 3000lux lighting, flash removal is checked via visual inspection equipment (resolution 0.01mm), requiring no visible burrs on earplug surfaces and key areas (e.g., sealing lips) with burr height ≤0.01mm.
Function Testing: Samples undergo noise reduction performance testing (SNR value) and airtightness testing (0.05MPa pressure holding for 10 seconds without leakage) to ensure core earplug functions are unaffected by deflashing.
V. Analysis of Cryogenic Deflashing Technical Advantages
1. High Precision and Skin-Friendliness Protection
The Liquid nitrogen flash machine achieves selective flash embrittlement through precise temperature control, combined with CNC sandblasting trajectories, ensuring deflashing precision of ±0.01mm while preserving the soft touch of silicone, avoiding surface hardening from traditional mechanical deflashing.
2. Efficiency and Cost Advantages
Single equipment processes 800–1200 earplugs per hour, 20 times more efficient than manual deflashing. Nylon sand can be reused over 60 times, with liquid nitrogen consumption only 0.2–0.5L/part, reducing costs by 50%.
3. Material Adaptability and High-Cleanliness Production
Compatible with various silicone materials like food-grade and medical-grade, the process is chemical-free. A sealed sandblasting chamber design ensures dust emission ≤3mg/m³, meeting high-cleanliness standards for medical and baby products.
4. Process Flexibility and Customized Production
The equipment supports one-click parameter switching for different hardness silicones. Combined with local finishing by the small sand blasting machine, it meets diverse design needs for earplugs, enabling fully automated production from ordinary to professional-grade products.
Conclusion
From liquid nitrogen cryogenic embrittlement to sandblasting finishing, the deflashing system composed of Liquid nitrogen flash machine, Sand blasting machine, and small sand blasting machine achieves three-stage processing of "cryogenic embrittlement-kinetic energy removal-fine polishing", significantly improving surface quality and production efficiency while ensuring wearing comfort and functional integrity of silicone earplugs. With its automated and high-precision advantages, this technology provides standardized solutions for silicone earplug manufacturing in medical, consumer electronics, and other fields, driving industry upgrading to intelligent and high-quality production.
