Rubber Molding is a process through which you can produce use-end rubber products like footwear, automotive applications and storage products. Liquid silicone rubber (LSR) is used for molding process. It is a non-reactive, stable, low viscosity compound which is resistant to extreme temperature. It comes in one or two-part polymer and may contain fillers to improve its properties or reduce cost.

Rubber can be molded through any of these three processes.

Injection Molding Process

Here, LSR is fed into an injection barrel through a screw which then travels through a runner. From there it travels through the sprues and get collected into the mold cavity. Once it fills the mold, it is cured and later removed from the mold. It is the most preferred method for rubber molding as it is a continuous and consistent process. It is used in mass production as it is cost effective.

Compression Molding

It is one of the simplest methods of rubber molding. Here, the uncured rubber is manually placed on the bottom plate of the mold cavity. Once the two halves are closed, the rubber fills the cavity perfectly, spilling out the excess rubber. Once it is cured under high pressure and temperature, it is removed from the mold. This process is used for low volume production and is also ideal for expensive materials.

Transfer Molding

Unlike Compression Molding, rather than directly placing the uncured rubber inside the mold, it is placed on a transfer pot on the top half of the machine. It forces through the sprues and enters the mold cavity. It is then vulcanized through heat and pressure and later removed from the cavity. This method is less expensive and suitable for complex design.

Plastic Molding

By using liquid polymer, plastic can be molded into various shapes and sizes. There are various molding process practised in the industry. The most common ones are:

Injection Molding

Here, polymer resin in form of pellets is gravity fed into a funnel shaped container called hopper. It then passes through a heated chamber with the help of rotating screws. The melted liquid is forced into a mold. Once it is cooled down, it is removed through the pin. This process is used for mass production as it is quite economical.

Blow Molding

In this method, the polymer resin is melted and formed into a hollow tube called parison. From the tube, polymer is forced into the two halves of the mold cavity. Here the air pressure pushes the liquid around the sides of the mold upon which it takes the form of the mold. The parison can be formed through extrusion, injection or stretch blow method. They are typically used for making plastic bottles.

Compression Molding

Instead of pellets, preheated polymer is placed into the bottom half of the mold cavity plate. Once the cavity is closed, the plastic is cured due to high temperature and pressure. Once it cools down, it is removed from the cavity. The end product contains superior strength properties. This method is used for making complex design such as auto parts.

Rotational Molding

In this process, polymer powder is fed inside a three-dimensional heated chamber. Once polymer is inserted, the chamber rotates bi-axially. As the chamber rotates; the polymer melts and coats the walls of the mold. Once it cools down, the polymer is able to retain its shape. The end product is of high strength and uniform quality.

Custom Molding

Catering to specific demands of customers, custom molding is practised by various companies. By using Injection molding and Compression Molding techniques, both rubber and plastic can be molded into complex designs of varying sizes.