The Process of Rubber Extrusion
Used often in sealing applications, rubber extrusions are continuous profiles and named after their manufacturing method. Rubber extrusions can vary from simple to complex designs. Although extrusion isn’t the only way to produce a length of rubber, it is however the most effective way of manufacturing continuous, consistent lengths of profiled rubber. So what is the process of rubber extrusion? Continue reading further to find out more.
How Does Rubber Extrusion Work?
The process of rubber extrusion includes the use of a die and an extruder. A die is essentially a metal disk with an opening that has been machined to create the profile required. An extrusion die is a very precise tool made from a blank of steel. The shape of the opening in the die will match the finished cross section of the extruded rubber. Once the rubber material is placed in the extruder, the rubber will be forced through the die via pressure that builds up from the revolving screw in the extruder.
The extruder, a rotating screw, can be found behind the die. The rotating screw sits inside a cylinder, and this is where the raw material(rubber), along with pigment and other special ingredients are placed. As the screw rotates, it forces the uncured rubber out through the die cavity. By way of pressure, the rubber exits the extruder where it must be cured.
Curing will take place in a variety of ways that can include ovens, microwaves or water. During vulcanization, the extruded rubber will shrink or swell in its cross section, as well as its length. This shrinking or swelling will depend on the type of rubber compound being used. Because of rubber’s tendency to swell, extrusions will require tolerances on their cross sections. The final process of rubber extrusion will be the finishing of the product. In the finishing step, coatings are added and the rubber extrusions are then cut to length.
Extruded Rubber vs. Molded Rubber
Rubber has endless uses in almost every industry. From coatings to parts and seals, rubber has multiple benefits and is produced by either extrusion, compression or injection molding. Compression molding is one of the oldest methods and is most suitable for creating larger, intricate parts by way of a four stage process. Extrusion, as noted above, is for creating sealing applications and hoses. Extrusion comes in two forms, hot and cold fed. Injection molding is more commonly found in thermoplastic manufacturing, and is done so in a six stage process. Each type of process has its own advantages and disadvantages depending on the application it is used for.
Advantages of the Rubber Extrusion Process
According to the ACS, the American rubber industry became the largest as well as the most technologically advanced in the world by the early 20th century. By the late 30s, the U.S. was already using half the world’s supply of natural rubber. With the creation of synthetic rubbers and processes like extrusion, concerns of shortages became a thing of the past. Some common synthetic rubber compounds used in the extrusion process are neoprene, silicone, nitrile SBR, and synthetic polyisoprene. There are many advantages of rubber extrusion processing that include:
- Minimal waste
- Efficient, continuous process
- Made in a variety of shapes and sizes
- Products are flexible and lightweight
Extruded, synthetic rubber products can range in a variety lengths or shapes to meet an array of applications. Common extruded rubber products include door and window seals, tubing, connectors, vibration reducers, gaskets and more.