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The 4 Most Common Rubber Manufacturing Processes

By Brittney Hoover 2 years ago 91603 Views No comments


When it comes to producing rubber products, multiple manufacturing processes exist. Each manufacturing process has particular benefits that make it the ideal choice for manufacturing certain types of products. Knowing the manufacturing processes can help you understand cost implications and tradeoffs. Some of the most common rubber manufacturing processes are extrusion, latex dipping, molding, and calendering.

Extrusion begins with an unvulcanized compound being fed into an extruder. Once it’s inside the extruder, it gets carried forward to a dye, which is a specialized manufacturing tool used to shape the rubber. Once the compound reaches the dye, the pressure from the process forces it through the opening of the extruder. Then, the extruded product will need to be vulcanized prior to being defined “usable”. It is important to note that any rubber compound must have a “cure package” already blended in prior to vulcanization. During the vulcanization process the rubber may swell or shrink, after vulcanization the length of the rubber extrusion may be impacted as well. Extrusion manufacturing has the advantage of being able to produce products in high volumes at a lower production cost. Some of the common rubber products produced from extrusion includes profiles, cord, tubing, and gaskets.

Latex dipping occurs when thin walled molds are immersed into latex compounds and then slowly withdrawn. The thickness of the dipped product can easily be increased by simply re-dipping the product in the latex compound. After the dipping process occurs, the product is finished by vulcanization. Depending on the finished dipped product, post treatments may also be needed. At the Hygenic Corporation we use a proprietary dipping method to achieve the optimal finished product. The main advantage of dip molding includes being able to dip latex products with thinner walls and to create more complex shapes than extrusion. Some of the common dip molded products include rubber gloves, grips, bladders, balloons, tubing, etc.

Molding is comprised of three main manufacturing processes, which are compression molding, transfer molding, and injection molding. Compression molding is the oldest and least expensive method. With compression molding, a rubber compound is formed into a blank (chunk of rubber); the blank then gets placed into a mold cavity to be shaped. The heating time is slow, which results in a long curing time; the heating can vary from three minutes for thin walls to several hours for thick walls. Some advantages of this method include being suitable for rubber compounds with large surface areas, and the ability to be used for rubber compounds with high viscosity and poor flow properties. On the down side, the process is time consuming with a low production rate. Some of the common products made with the compression molding process include seals, o-rings, electrical insulators, and silicone wrist bands.

Transfer molding is a natural progression in development to limit the disadvantages of compression molding. The process starts out with a blank being loaded in the chamber, which is then distributed into several cavities. In this beginning stage, pre-heating takes place in the rubber, forcing the rubber to flow through channels. This pre-heating reduces the curing time and allows the rubber to flow easier and fill mold cavities efficiently. However, the molds are more complicated and expensive.

Injection molding is the third most common molding process. With injection molding, the press unit and injection unit act as two separate entities with separate controls. The press unit allows for molds to be placed horizontally or vertically. An extruder unit can also serve several presses by moving in a pre-programmed pattern. All of these result in short injection processes with high amounts of pre-heating. With this type of molding, the handling of blanks is eliminated, processes can be automated and difficult cavities and flow channels can easily be filled.

The last most common manufacturing process is called calendaring, which works by forcing softened material into the center of counter-rotating rollers. Rollers compact the material and the overall thickness of the product is determined by the gap distance between cylinders, which can be adjusted for varying product thicknesses. Once the material passes through cooling rollers, it must be vulcanized. This process works best to produce sheets or films of rubber. Some benefits of calendering include control over product thickness and the ability to produce parts thinner and wider than with the extrusion. However, calendering has high operating costs compared to other processes.

Each manufacturing process is ideal for producing certain types of rubber products. Understanding the processes available can make planning for manufacturing a lot easier because each process has its own cost and time limitations. Although The Hygenic Corporation only specializes in a few of the main rubber manufacturing processes, they will work with companies to help them decide which manufacturing process would be most suitable based on their individual product needs.

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