Unveiling the modern tennis ball production line: How is a tennis ball made?

1. Production steps of tennis balls

Raw material preparation: from raw rubber to bladder

(1) Rubber processing

Raw material source: Raw rubber is shaped, extruded and heated to form a hard rubber block.

Core molding: The rubber block is injected into a hemispherical mold and formed into a hemispherical bladder under high temperature and pressure, which looks like a "chocolate ball".

(2) Bladder synthesis

The two hemispheres are bonded into a complete hollow sphere by gluing and extrusion, which constitutes the core of the tennis ball.

"Sonic popcorn" process: The bladder is placed in a vibrating barrel and shaken to enhance elasticity and texture.

Felt wrapping: precise matching and bonding

(1) Felt preparation

The felt raw material (usually wool or synthetic fiber) is cut into **"dog bone shapes"** (similar to oval bandages), and each ball requires two pieces of felt wrapping.

Adhesive coating: The felt is coated with white adhesive through a roller to ensure a firm bond with the bladder.

(2) Automated packaging

The robotic arm fits the felt precisely to the bladder, and then pressurizes and dries it in liquid form to make the felt fit the ball perfectly.

Quality inspection and packaging

(1) Strict quality inspection

Bounce test: The tennis ball needs to be dropped from a height of 2.54 meters, and the rebound height should be between 1.35-1.47 meters (ITF standard).

Weight and diameter: The standard match ball weighs 56.7-58.5 grams and has a diameter of 6.54-6.86 centimeters.

(2) Airtight packaging

The tennis ball is sealed in a pressurized can to keep the internal air pressure stable to ensure the freshness of "out of the can".

It is left to stand for 5 days before leaving the factory to further solidify the adhesive and test the airtightness.

Technological innovation: environmental protection and intelligent trends

(1) Environmentally friendly process

The traditional zinc stearate coolant (harmful to the environment) is replaced by air drying technology to reduce pollution.

Layered lamination technology: Rubber layers with different characteristics are laminated together to improve durability and elasticity.

(2) Intelligent manufacturing

AI quality inspection system: Visual inspection is used to remove unqualified balls wrapped in felt.

Automated sorting: Robotic arms classify and package by grade (professional/amateur).

2. Precautions for operation of tennis production line

Raw material quality control

Rubber raw material testing:

Check the hardness, elasticity and impurity content of the rubber to ensure that it meets the ITF (International Tennis Federation) standards.

Avoid using inferior rubber, otherwise it may cause the bladder to deform or lack elasticity.

Felt material screening:

Wool/synthetic fibers must be uniform and free of lumps, with a thickness error of ≤0.1mm.

Felt adhesives must be non-toxic and resistant to high temperatures (to avoid falling off during competition).

Production environment management

Temperature and humidity control:

The workshop temperature should be maintained at 20-25℃ and the humidity at 50%-60% (to prevent rubber oxidation or felt from getting damp).

High temperatures may cause the adhesive to cure prematurely, and low temperatures may affect the elasticity of the rubber.

Dust and static electricity protection:

The felt cutting area must be equipped with dust collection equipment to prevent fiber drifting and affecting bonding.

Anti-static measures are required in the rubber processing area (static electricity may absorb impurities).

Core process operation specifications

(1) Ball bladder molding

The mold temperature must be stable at 160-180℃ and the pressure must be 8-10MPa to ensure that the rubber is fully vulcanized.

The hemispheres must be precisely aligned when bonding. Ball bladders with misalignment >0.5mm must be scrapped.

(2) Felt wrapping

The adhesive coating thickness must be uniform (0.2-0.3mm). Excessive application will cause the felt to harden.

After wrapping, it must be left to cure for 24 hours. Balls that are not completely dry must not enter the next process.

(3) Pressurized shaping

The shaping air pressure must be controlled at 0.8-1.0bar. Insufficient air pressure will cause the felt to wrinkle.

The shaping time is 30-40 minutes. Exceeding this time may cause rubber aging.

Key points of quality inspection

Bounce test:

Randomly inspect 10% of the finished products. Batches with unqualified rebound height (<1.35m or >1.47m) must be fully inspected.

Appearance inspection:

Felt seam width ≤1mm, no burrs or glue residue.

Air tightness test:

Vacuum to detect whether the ball bladder is leaking. Balls with a pressure drop rate of ＞5% are considered defective.

Equipment maintenance and safety

Daily maintenance:

Clean the residual rubber in the mold and check whether the heating element is aging.

Lubricate the joints of the robot arm to prevent jamming from affecting the wrapping accuracy.

Safe operation:

Workers need to wear cut-resistant gloves (felt cutting machine) and heat-resistant gloves (vulcanization area).

The emergency stop button must be tested regularly to ensure that production can be interrupted immediately in the event of a sudden failure.

Environmental protection and waste disposal

Waste recycling:

Rubber scraps can be crushed and re-melted (recycling rate must be ≥90%).

Waste felt needs to be sorted and processed, and synthetic fibers are sent to professional institutions for degradation.

Prohibited substances:

The use of dyes or plasticizers containing lead/cadmium is strictly prohibited (in compliance with EU REACH regulations).