Sealing ring lifting machine

4 month ago

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Dongguan YingSiDa Intelligent Technology Co., Ltd.

4 month

Product details

Comprehensive Process and Technical Advantages of Removing Flash and Burrs from Silicone O-Rings with Cryogenic Deflashing Machine

In the processing of silicone products, the treatment of flash and burrs on O-rings directly impacts sealing performance and service life. Cryogenic deflashing technology, leveraging the composite process of low-temperature embrittlement and kinetic energy spraying, has become an efficient solution for silicone O-ring deflashing. This article details the standard process of removing flash from silicone O-rings using a Liquid nitrogen flash machine and deeply analyzes the 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 O-Rings

Flash Positioning: Flash distribution is identified via a visual inspection system (precision ±0.02mm), commonly found on parting surfaces, injection ports, and cross-sectional edges. Record burr thickness (typically 0.1-0.4mm) and silicone hardness (Shore A 40-70).

Flexible Fixture Design: Silicone O-rings are fixed with polytetrafluoroethylene (PTFE) fixtures. Arc-shaped slots suitable for different specifications (φ5-φ200mm) are designed to avoid deformation from stress concentration at low temperatures. Fixture surfaces undergo hydrophobic treatment to prevent silicone-metal adhesion affecting demolding.

2. Parameter Setting for Liquid nitrogen flash machine

Cryogenic Embrittlement Threshold: Equipment temperature is adjusted to -160℃~-196℃ based on silicone type, with a holding time of 10-15 minutes (e.g., food-grade silicone requires -180℃ for 12 minutes). This embrittles flash areas due to molecular chain contraction (hardness increases to Shore A 95), while maintaining elasticity of the main O-ring (elongation ≥350%).

Spray Media Preparation: 0.1-0.2mm nylon sand (Shore D 75-85 hardness) is used, pre-dried at 120℃ for 4 hours to ensure no moisture residue, avoiding impact on silicone surface properties.

II. Liquid Nitrogen Cryogenic Deflashing: Flash Embrittlement and Batch Removal

1. Gradient Cryogenic Embrittlement

Staged Cooling: After starting the Liquid nitrogen flash machine, O-rings 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 40-80μm, with a circulating fan (wind speed 10m/s) ensuring uniform flash cooling and surface temperature difference ≤2℃.

Temperature Field Monitoring: Real-time monitoring via infrared thermography focuses on heat dissipation blind spots like cross-sectional R corners and grooves. Auxiliary nozzles are added if necessary to ensure consistent flash embrittlement and avoid incomplete local treatment.

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 60-90m/s. "30° angled spraying" is used for thin flash below 0.2mm, while cross-trajectory spraying is applied to thick flash (>0.3mm), with single-pass removal ≤0.05mm to prevent over-blasting causing O-ring cross-sectional size out-of-tolerance (control tolerance ±0.03mm).

Automated Trajectory: For irregular O-rings (e.g., with lip structures), CNC-generated contoured spraying paths ensure no flash residue in key areas like sealing surfaces and inner holes, while protecting lip precision to avoid affecting sealing performance.

III. Sandblasting Finishing: Surface Quality Optimization

1. Coarse Sandblasting with Sand blasting machine

Batch Processing: For conventional silicone O-rings (e.g., mechanical seals), a turntable-type Sand blasting machine is used. Workpieces are loaded with 0.2-0.3mm glass beads (roundness ≥98%) and sandblasted at 40rpm for 6 minutes to remove residual micro-flash after cryogenic deflashing, reducing surface roughness from Ra 8μm to 2μm.

Process Parameters: Sandblasting pressure 0.3MPa, spraying distance 12cm. The turntable angle is adjusted via servo motor to ensure uniform sand exposure on O-ring inner/outer diameters and cross-sections, avoiding local over-blasting that could roughen the surface.

2. Fine Trimming with small sand blasting machine

Local Micro-Processing: For medical-grade silicone O-rings, a small sand blasting machine is used for targeted finishing. 0.05mm corn starch sand is selected, and secondary sandblasting is performed on critical areas like sealing lips and parting surfaces under a 20x microscope to eliminate 0.01mm-level burrs without damaging sealing surfaces (surface roughness Ra≤0.8μm).

Static Control: An ion air bar (wind speed 10m/s) is activated during sandblasting to prevent static electricity from adsorbing sand particles on silicone surfaces, affecting subsequent sterilization or assembly precision.

IV. Post-Processing and Quality Verification

1. Cleaning and Performance Recovery

Ultrasonic Cleaning: O-rings are placed in an ultrasonic tank with neutral detergent (frequency 40kHz) for 4 minutes to remove surface sand and oil, then rinsed three times with deionized water. Medical-grade products require additional pure water spraying (conductivity ≤1μS/cm).

Stress Relief: After cleaning, O-rings are kept in a 60℃ thermostatic chamber for 1.5 hours to eliminate internal stress from cryogenic deflashing, restoring silicone elasticity and ensuring compression set ≤8% to meet sealing performance 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 sealing surfaces and non-functional surface burr height ≤0.02mm.

Sealing Performance Testing: Samples undergo air pressure testing (0.5MPa pressure holding for 1 minute) with leakage rate ≤0.03%; for high-pressure scenarios (e.g., hydraulic systems), 2MPa water pressure testing is required to ensure sealing reliability of O-rings after deflashing.

V. Analysis of Cryogenic Deflashing Technical Advantages

1. High Precision and Consistency

The Liquid nitrogen flash machine achieves selective flash embrittlement at -196℃, combined with CNC sandblasting trajectories, realizing ±0.01mm-level deflashing precision. Consistency is improved by 85% compared to traditional manual deflashing, especially suitable for high-precision requirements in medical and aerospace fields.

2. Efficiency and Cost Advantages

Single equipment can process 600-1000 O-rings per hour, increasing efficiency by 15 times compared to manual deflashing. Nylon sand can be reused over 50 times, with liquid nitrogen consumption only 0.5L per piece, reducing comprehensive costs by 45% and suitable for mass production.

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. A sealed sandblasting chamber design is used, with dust emission ≤5mg/m³, complying with ISO 14001 standards and suitable for high-cleanliness scenarios.

4. Process Flexibility and Automation

The equipment supports one-click parameter switching for different hardness silicones. Combined with local finishing by the small sand blasting machine, it adapts to various cross-sectional structures like O-shaped and Y-shaped, realizing fully automated processes from roughing to finishing and reducing manual intervention errors.

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 while ensuring sealing performance of silicone O-rings. This technology not only breaks through the efficiency bottleneck of traditional manual deflashing but also provides standardized solutions for silicone seal processing in medical, automotive, aerospace, and other fields with its automated and high-precision advantages, promoting the industry's upgrading to intelligent manufacturing.