Comprehensive Process and Technical Advantages of Removing Flash and Burrs from Silicone Seals with Liquid Nitrogen Flash Machine
In the processing of silicone products, the treatment of flash and burrs on seals directly affects sealing performance and service life. Liquid nitrogen cryogenic deflashing technology has become the mainstream solution for silicone seal deflashing due to its high efficiency and precision. This article details the full process of removing flash from silicone seals using a Liquid nitrogen flash machine, and introduces the application and technical advantages of Sand blasting machine and small sand blasting machine in fine processing.
I. Pretreatment: Dual Preparation of Workpieces and Equipment
1. Initial Inspection and Fixing of Silicone Seals
Flash Positioning: Flash distribution is identified via a visual inspection system (precision ±0.02mm), commonly found on parting surfaces, injection ports, and lip edges. Record burr thickness (typically 0.1-0.5mm) and silicone type (e.g., food-grade silicone, medical-grade silicone).
Flexible Fixture Design: Silicone seals are fixed with polytetrafluoroethylene (PTFE) fixtures. For thin-walled structures (wall thickness ≤1.5mm), arc supports are designed to avoid deformation from stress concentration at low temperatures. Fixture surfaces undergo hydrophobic treatment to prevent silicone-metal adhesion.
2. Parameter Setting for Liquid nitrogen flash machine
Cryogenic Embrittlement Threshold: Equipment temperature is adjusted to -150℃~-196℃ based on silicone hardness (Shore A 30-80), with holding time set to 10-20 minutes. This embrittles flash areas due to molecular chain contraction (hardness increases to Shore A 90+), while maintaining elasticity of the main seal (elongation ≥300%).
Spray Media Preparation: 0.1-0.2mm nylon sand (Shore D 70-80 hardness) is used, pre-dried at 120℃ for 4 hours to avoid moisture affecting spraying performance and prevent silicone from absorbing water vapor.
II. Liquid Nitrogen Cryogenic Deflashing: Flash Embrittlement and Batch Removal
1. Gradient Cryogenic Embrittlement
Staged Cooling: After starting the Liquid nitrogen flash machine, seals are pre-cooled at -80℃ for 5 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 50-100μm, with circulating airflow (wind speed 8-12m/s) ensuring uniform flash cooling.
Temperature Field Uniformity: Infrared sensors monitor to ensure surface temperature difference ≤3℃, particularly focusing on heat dissipation blind spots like lips and grooves. Airflow deflectors are added if necessary to optimize cold air circulation for consistent flash embrittlement.
2. Low-Pressure Sandblasting for Flash Removal
Kinetic Energy Matching: After freezing, the equipment drives nylon sand with 0.3-0.5MPa compressed air at 60-100m/s. "Parallel spraying" (15°-30° angle) is used for thin flash below 0.2mm, while cross-spraying paths are applied to thick flash (>0.3mm), with single-pass removal ≤0.05mm to avoid over-blasting that could cause seal deformation.
Automated Trajectory: For irregular seals (e.g., Y-shaped, O-shaped), CNC-generated contoured spraying trajectories ensure no flash residue in key areas like lips and sealing surfaces, while protecting the precision of sealing lips (control tolerance ±0.03mm).
III. Sandblasting Finishing: Surface Quality Optimization
1. Coarse Sandblasting with Sand blasting machine
Batch Processing: For conventional silicone seals (e.g., water pipe joints, home appliance seals), a turntable-type Sand blasting machine is used. Workpieces are loaded with 0.2-0.3mm glass beads (roundness ≥98%) and sandblasted at 30-50rpm for 5-8 minutes to remove residual micro-flash after cryogenic deflashing, reducing surface roughness from Ra 6.3μm to 1.6μm.
Process Parameters: Sandblasting pressure 0.2-0.4MPa, spraying distance 10-15cm. The turntable angle is adjusted via servo motor to ensure uniform sand exposure on all seal surfaces, avoiding local over-blasting that could roughen the surface.
2. Fine Trimming with small sand blasting machine
Local Micro-Processing: For high-precision silicone seals (e.g., medical catheters, aerospace seals), a small sand blasting machine is used for targeted finishing. 0.03-0.08mm corn starch sand (HV 200-300 hardness) is selected, and secondary sandblasting is performed on critical areas like sealing lips and grooves under a microscope (10-20x) to eliminate 0.01mm-level burrs without damaging sealing surfaces.
Static Control: An ion air bar (wind speed 8-12m/s) is activated during sandblasting to prevent static electricity from adsorbing sand particles on silicone surfaces, which could affect subsequent assembly sealing performance.
IV. Post-Processing and Quality Verification
1. Cleaning and Performance Recovery
Ultrasonic Cleaning: Seals are placed in an ultrasonic tank with neutral detergent (frequency 40kHz) for 3-5 minutes to remove surface sand and oil, then rinsed twice with deionized water. Medical-grade seals require additional pure water spraying (conductivity ≤1μS/cm).
Stress Relief: After cleaning, seals are kept in a thermostatic chamber (60-80℃) for 1-2 hours to eliminate internal stress generated during cryogenic deflashing, restoring silicone elasticity and ensuring compression set ≤10%.
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 sealing surfaces and non-functional surface burr height ≤0.02mm.
Sealing Performance Testing: Samples undergo water pressure testing (0.5-2MPa) and airtightness testing (air pressure 0.3MPa, pressure holding 30s) to verify sealing performance, with leakage rate ≤0.05%.
V. Technical Advantages of Liquid Nitrogen Cryogenic Deflashing
1. High Precision and Consistency
The liquid nitrogen flash machine achieves selective flash embrittlement at -196℃, combined with CNC sandblasting trajectories, ensuring flash removal precision of ±0.01mm. Consistency is improved by 90% compared to traditional manual deflashing, especially suitable for micron-level precision requirements of medical-grade seals.
2. Efficiency and Cost Advantages
A single Liquid nitrogen flash machine can process 500-1000 seals per hour, increasing efficiency by 15-20 times compared to manual deflashing. Nylon sand can be reused 50-80 times, with liquid nitrogen consumption only 0.3-0.8L per piece, reducing comprehensive costs by over 40%.
3. Material Adaptability and Environmental Friendliness
Compatible with various silicone materials such as food-grade and medical-grade, the deflashing process is free of chemical pollution. Inert gas-protected sandblasting is used, with dust emission ≤5mg/m³, complying with ISO 14001 environmental standards, suitable for high-cleanliness fields like medical and food industries.
4. Process Flexibility and Automation
The equipment supports one-click parameter switching for different silicone hardnesses. Combined with local finishing by the small sand blasting machine, it meets deflashing needs for various seals such as O-shaped, Y-shaped, and combined types, enabling full-process automated production.
Conclusion
From cryogenic embrittlement to sandblasting finishing, the silicone seal deflashing system composed of Liquid nitrogen flash machine, Sand blasting machine, and small sand blasting machine achieves "precise embrittlement-kinetic energy removal-fine polishing" three-stage treatment, significantly improving surface quality while ensuring sealing performance. This process not only solves the efficiency and precision bottleneck of traditional manual deflashing but also provides a reliable solution for silicone seal processing in high-end fields such as medical, aerospace, and food industries with its automated and environmentally friendly technical advantages.
