From rubber to felt: revealing the core process of tennis production

1. Raw material processing and rubber core molding of tennis production line

Natural rubber selection: purchase high-purity rubber, and detect heavy metal content by X-ray.

Compound formula modulation: natural rubber and styrene-butadiene rubber are mixed in a ratio of 7:3, sulfur (1.2-1.8%), carbon black (20-30%), etc. are added, and the internal mixer is mixed at 150-160℃ for 6-8 minutes.

Preforming cutting: The rubber block is cut into a cylinder with a diameter of 65mm and a weight of 38±0.5g, with a thickness error of ±0.1mm.

Hemisphere molding: Injection into a 160℃ mold, 100 tons of pressure to form a hemisphere with a wall thickness of 2.8mm, and the laser scanning diameter deviation is <±0.15mm.

Plasma treatment: Argon plasma bombards the inner wall of the hemisphere for 30-60 seconds to improve the bonding strength (the contact angle is reduced from 95° to 35°).

Hemisphere bonding assembly: coating with chloroprene glue (0.08g/cm²), ultrasonic vibration pressing (30N pressure + 80kHz), airtight test leakage rate <0.5psi/min.

Secondary vulcanization shaping: 120℃ hot air furnace for 2 hours, eliminating residual stress, and improving the elastic modulus stability by 15%.

Sonic detonation treatment: 150dB low-frequency sound wave bombardment for 30 seconds, balanced molecular chain arrangement, and the standard deviation of the bounce height is reduced to ±0.3 inches.

2. Felt processing and ball bonding

Wool blending preparation: 70% Merino wool + 30% nylon 6.6, wet-laid, unit weight 380±10g/m².

Dyeing and waterproofing treatment: acid dyeing at 98℃ for 45 minutes, fluorine-based waterproofing agent padding (water absorption <5%).

Three-dimensional laser cutting: CO₂ laser cutting "dog bone-shaped" felt (precision 0.1mm), single 35±0.05g.

Steam pre-stretching and shaping: 105℃ steam softening for 8 seconds, vacuum mold curvature matching degree>99%.

Adhesive spraying: water-based polyurethane glue (18±1g/m²) combined with isocyanate primer.

Robot precision fitting: six-axis robot positioning (error <0.5mm), rolling to remove bubbles (pressure 20N).

Segmented hot pressing curing: 80℃/5min→120℃/3min→60℃/10min, peel strength reaches 12N/mm.

Surface fluffing finishing: nylon brush (1500rpm) directional combing fluff, improve rotation performance by 15%.

3. Quality inspection and packaging

Dynamic balance test: 3000rpm rotation to detect center of mass deviation (<0.5mm), if out of tolerance, inject 0.01-0.05g weight glue.

ITF standard bounce test: 254cm free fall, rebound height 53-58 inches (the difference of the same can ball is <0.5 inches).

Abrasion resistance evaluation: Sandpaper (180 mesh) rubbed 2000 times, felt loss volume <15mm³.

Air pressure stability verification: 14.7±0.1psi initial pressure, drop ≤0.3psi after 5 days.

X-ray and UV detection: 3D scanning of internal structure, fluorescent glue to check the quality of bonding.

Aseptic nitrogen filling packaging: 1.2atm nitrogen is filled in tinplate cans, and the humidity adjustment card maintains 40-45%RH.

5-day tightness monitoring: Constant temperature storage (23±1℃) to confirm pressure stability.

Cold chain logistics distribution: Temperature control throughout transportation (15-25℃), environmental balance 48 hours before professional competition.

Key process highlights

Sonic detonation treatment: Optimize the rubber molecular structure through low-frequency sound waves, significantly improve the bounce consistency.

Dog bone-shaped felt design: Reduce the number of seams and enhance aerodynamic performance.

Helium mass spectrometer leak detection: The detection sensitivity reaches 3×10⁻⁷mbar·L/s, far exceeding the industry standard.