Rubber, like many other types of materials such as bronze, brass, ceramics, composites, plastics, silicone, precious metals, copper, aluminum and steel, can go through an extrusion process. A rubber extrusion process is used to produce various types of rubber components such as: tubes, C channels, shapes like C, E, H, L, T, U, forms like half rounds, rounds, rectangles, trapezoids, and hatch door seals, etc. These components are extensively used in many types of industrial applications such as: the printing industry, automobiles, chemical companies, electrical and manufacturing processes.
The process of extruding involves the forcing or pushing out of a material through a mold, which shapes the material the same as the mold. The extruded rubber products are later used at various sub assemblies to make items such as tires, seals, gaskets, rubber bumpers mounting pads, and vibration absorbers, etc. There is also an assortment of raw rubber materials that can be used for extrusion such as: gum rubber, neoprene, nitrile, dupont viton, EPR, NBR, Buna-N, flurocarbon, silicone, and Aflas, etc. The components can have a hardness value of between 40 to 90 durometers.
Rubber is a good material to extrude as it is water repellant, has elasticity, and is resistant to electricity. Both natural and synthetic rubber are used in rubber extrusions however synthetic rubber is more common as its characteristics are more resistant to aging, can better resist oils and chemicals and can keep its resiliency through a wider range of temperatures than natural rubber can.
The accuracy of the molds and dies that are used will influence the finish and the quality of the extruded parts. A well designed die, with the proper gates, vents and with a good internal finish should produce rubber parts of excellent quality. The die or mold has different areas that have tolerance class ratings from F1 to F4. A rating of F1 means that the particular areas or dimension should have a finish up to 10 micro inches, with no visible tool marks, while a rating of F4 means that the dimension will have a satin like finish. The dies and molds should be heat treated for longer life.
Rubber extruded components have areas or dimensions, where flash material is not permitted. The extruded components can later be: turned, milled, drilled or ground per the assembly requirements.