The process of rubber molding involves shaping raw rubber materials into functional products. While some products can be made by other rubber shaping processes such as cell casting and extrusion, the molding process has its own features that set it apart. Products that are made through rubber molding are enclosed in a mold cavity instead of a die, and can thus be made into complex and irregular shapes.
Rubber molding is a operation in which raw melted rubber takes form inside a mold. Many kinds of complex rubber products, such as rubber diaphragms and rubber seals, are made this way, due to the ability of the rubber molding process to precisely design a product so it fits perfectly into a piece of equipment without the risk of any kind of leakage. Products that are made to protect equipment, such as rubber washers and rubber grommets, must also be designed with precision, and are thus manufactured by rubber molding. These products can also be produced through rubber extrusion. However, extruding machines have much more limited capabilities. An extruder only has control over the X and Y axes, and are thus much more suited for the production of simpler rubber products such as rubber baseboards or rubber sheets. Rubber molding allows from design control over three axes due to the process involving a molding cavity instead of a die. Read More…
To one extent or another, molded rubber products span every industry. Since many manufacturing machines contain moving parts that can vibrate excessively, rubber washers and rubber bushings are installed to secure these moving parts and absorb vibration in an effort to protect the people operating them. Another component that can be used to absorb vibration is a rubber sheet. A rubber sheet is a large, thick sheet that reduces vibration and noise in a machine when placed underneath it. The reduction of vibration and noise can greatly improve overall safety and working conditions.
Rubber grommets are another useful component that is used extensively for industrial, consumer, and commercial purposes. Rubber grommets are made to fit around a hole in a surface, protecting wires or other hardware that must pass through it. Grommets can also protect the hole itself from wear or damage. Rubber grommets can be found protecting wires from becoming disconnected, or aligning the holes in desks which allow safe passage for computer wires.
The various types of rubber that can be molded include natural rubber, as well as synthetic rubber such as neoprene, foam rubber, EPDM, silicone rubber, and liquid silicone rubber. Natural rubber is the most widely known and has been used the longest. The first suspected use of rubber dates back to Mayan civilizations around 1600 BCE, but it has been used industrially since the 19th century. During the 20th century, natural rubber was scarce, thus leading to the development and flourishing of synthetic rubber. Today, less than half of all rubber materials manufactured worldwide are made from natural rubber.
The first synthetic rubber to be produced on an industrial scale is neoprene. While neoprene and other synthetic rubbers have the same positive qualities as natural rubber, they are not without their drawbacks. Synthetic rubbers such as EPDM, neoprene, and silicone can be made corrosion-resistant, heat-resistant, ozone resistant, inert with certain chemicals, and made with varying degrees of properties such as rigidity, flexibility, durability, and strength. Because of the existence and capabilities such as synthetic rubber, industries such as health care can make use of numerous applications while reducing the health risk. For instance, alternative materials are available for people with latex allergies, and intravenous fluids can pass safely through silicone tubing without causing allergic reactions.
The types of rubber molding include injection molding, liquid injection molding, compression molding, and transfer molding. All four methods have their similarities; however, injection molding is used more widely than any other method. The first step in the injection molding process involves collecting raw rubber material, known as stock. The stock is then placed into a hopper that is suspended over a conveyance channel. The stock is then released, and processed through a channel that features a large turning screw. By the time the stock reaches the end of the channel, it is completely melted as a result of a combination of the heating elements within the channel, and the friction caused by the screw’s motion. At the end of the channel is a mold cavity into which the molten rubber is injected.
The elements of heat and pressure work together to ensure that the molten rubber fills the cavity entirely, down to the very contours of the mold, and is uniformly distributed. The molten rubber is allowed to cool and harden within the mold, and can be safely removed from the mold cavity once it reaches a solid state. Once removed, the mold could have certain imperfections such as seams. If this is the case, the rubber product may have to undergo further processing if necessary. It is possible to add a variety of finishes and textures to the final product to add an aesthetic touch. For industries such as medical, aerospace, and electronics that require an injection molded product to be of a certain design, custom molding is also available. Although custom rubber injection molding is more costly, the cost is much lower in comparison than other methods of rubber manufacturing.