Rubber molding changes natural rubber from its raw, uncured form to a final, high-quality, usable product. The process utilizes high pressure and heat to speed the rubber’s curing process. Rubber compression molding, injection molding, and transfer molding are the three main methods of transforming uncured, raw rubber into desired shapes and end products.
Compression Molding
Manufacturers use heated mold cavities to cure raw rubber during compression molding. Thermoplastic rubber and thermoset plastics are the uncured materials that are commonly used in compression molding. During the compression molding process, a hydraulic press applies high pressure to the mold cavity. Common types of hydraulic compression machines used in rubber manufacturing include:
- Benchtop presses
- Wet compression molding machines
- Cold compression molding machines
Final cured rubber products usually require cleaning and cutting to remove any flashing, or excess materials, that might distort their shapes. However, compression molding creates products that are free from gate vestige, or extra material at the seams of the molds. Compression molding also does not cause shear strain, or misshaping along the cross sections, on the final, cured product.
Another advantage of compression molding is its ability to produce harder and stiffer cured rubber materials that can’t be melted again. Compression molding helps make kitchenware like pot handles, automotive parts like tires, medical equipment like syringe stoppers, and electrical components like switches.
The mold cavity’s uncomplicated design and low production and maintenance costs make compression molding an affordable option.
Injection Molding
Injection molding is a type of rubber molding that changes raw rubber into accurate and precise final products by stripping raw rubber materials and injecting them into mold cavities for vulcanization, or chemical treatment, and curing. The injection molding process is suitable for manufacturing final products that will experience heavy usage.
Liquid injection molding, thermoplastic rubber injection, and organic rubber injection are the most common types of injection molding. Some of the polymers used in injection molding are natural rubber, liquid silicone rubber, and nitrile rubber.
Final cured rubber products made by injection molding are strong and durable. Injection molding is suited for mass production, which enables manufacturers to increase product output and profits. Instead of hydraulic presses, injection molding uses external heaters to compress the mold. The application of regulated heat speeds up the rubber’s curing process, saving time for manufacturers.
Transfer Molding
Manufacturers use transfer molding to make products with high precision and complicated configurations. The transfer molding process produces gas valves, hydraulic seals, and connector seals. A transfer molding machine has a container fitted on its top that has sprues. Raw rubber pellets enter the machine’s mold cavity through the sprues for heating and curing.
Transfer molding uses an enclosed mold cavity, making the process more environmentally friendly than compression molding. The ability to use several mold cavities at once during transfer molding reduces production time.
Contact a Rubber Molding Company
Automotive, electrical, print, agricultural, medical, and aerospace industries rely on rubber molding professionals for high-quality rubber products. When looking for a rubber product manufacturer, conduct thorough research based on your product specifications, types of raw rubber materials, and the molding processes of each company to find the highest-quality company and products.
