Custom Manufacturing of Gaskets, Seals, Washers
Nonmetallic gasketing can be produced through die-cutting techniques from rubber (solid, open and closed cell) sponge, cork, and cork/rubber. Gasket types can be adhesive backed, spliced endless, molded, extruded, die cut and hand fabricated.
Extrusion processes yield profiles, shapes, tubing and cord. Materials suited for extrusion are natural rubber, synthetic rubber and plastics. Production facilities should be flexible enough to regulate hardness, density and color.
The extrusion die is made by cutting an opening in a blank of steel. The opening is shaped to form the rubber into the desired cross section as it is forced through the die by pressure from the revolving screw of the extruder. Making a die is an art developed by years of experience. The die is made for a particular extruder and a particular compound.
Extruded rubber products normally must be vulcanized before it is used. During the vulcanization, the extrusion will swell or shrink in the cross section and length depending on the compound used. After vulcanization a length of extrusion has a tendency to be reduced in dimension more in the center than the ends. Extruded product is vulcanized either in a heat pressure vessel (static vulcanization) or by the continuous vulcanization process. A great many variables are encountered in the extrusion process which make it necessary to allow more liberal tolerances than for molded parts. A design engineer should have a general knowledge of the extrusion process and its variables in order to design parts that can be extruded at reasonable cost.
Solid-rubber molding covers conventional compression, injection and transfer manufacturing of a variety of materials. Resulting products are O-rings, bumpers, end caps, tips and grommets.
Tubing extruded to size and cut to length by various methods is suited for washer and ring production. Tight-tolerance parts are mandrel cured (insertion of steel rod into inside diameter), ground to size on the outside diameter, or lathe cut to precise lengths. Coarse tolerances can be simple extrusion, high-speed or guillotine cut.
The joining of the ends of stock cut from coils is employed to form O-rings, rings, large diameters or cross sections used for sealing. Gaskets for large cargo doors, industrial vacuums, and seats for sealing are among typical applications.
Certain gasket/seal manufacturers offer rubber-to-metal bonding that uses natural rubber and synthetics such as Viton and urethane. Tolerances are achieved by grinding to exact diameters, straight or crowned.
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