Rubber extrusion is a process that is used to manufacture a number of rubber components such as: sheet and card stock, O Rings, piping expansion joints, ducting expansion joints (insulated for high temperatures, elastomers, metallic types), HVAC products, flexible braided connectors, bellows, pump connectors, compensators and pipe guides, etc.
Extruding is the technique of forcing or pushing out rubber through a mold to shape it. Because it is difficult to push rubber, most rubber extrusions are pieces of rubber that have been molded. Rubber is a good material to extrude as it is water repellant, has elasticity, and is resistant to electricity. Both natural and synthetic rubber is 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 extrusion products are made from various types of rubber such as neoprene, nitrile, SBR, EPDM, viton, silicone, urethane, Teflon, sponge, gum rubber, EPR, NBR, Buna-N, flurocarbon, and Aflas, etc. Extruded rubber components have a hardness ranging from 10 to 90 durometers. The products are often used in material handling equipment such as: heavy duty lifters, little grabbers, two man lifters, single cup lifters, double cup lifters and medium duty lifters. They are also used to make items such as: grommets, bumper-like grommets, gaskets, tires, car bumpers, rubber seals, adhesives, tack, stem, screws, recess, bushing, caps, suction cups, vibration absorbers, lab stoppers, rubber balls, channels and strips like U, P, L, E, mounts and for compression, flex bolts, platform, lattice, shock, leveling and channel L.
Rubber extrusion may be used to deliver the final product or further machines using tools such as turning, milling and drilling may be used to finish it.