O-Ring
A doughnut-shaped object, or torus, that functions as a seal, blocking the passage of liquids or gases, by being compressed between the two mating surfaces comprising the walls of the cavity (gland) into which the ring is installed
Off register
Eccentric O-ring cross-sectional radii caused by lateral shift of one mold cavity relative to the other
Oil Resistant
Ability of vulcanized rubber to resist swelling and other detrimental effects of exposure to various oils
Orange Peel
A surface finish on a molded part that is rough and splotchy. Usually caused by moisture in the mold cavity
Oscillating Seal
Most commonly used in faucet valves, in this application the inner or outer member of the gland moves in an arc around the axis of a shaft. Movement is limited to a few turns in one direction and a few turns in the return direction (i.e. faucet on, faucet off)
Outgassing
Primarily occurring in vacuum situations, the volatile (evaporative) components of some rubber compounds may become vaporized in the vacuum and released (outgassed) by the compound into the surrounding environment
Overflow
A designed escape reservoir for rubber compound used to insure mold cavity fill and also allowance for excess compound
Overflow Groove
A groove around the periphery of a mold cavity used to accept any excess material from the cavity during molding. Additional material beyond that which is required to fill the cavity is usually introduced into the cavity to ensure that the part is completely formed and to minimize the presence of entrapped air and voids
Oxidation
The reaction of oxygen with a rubber compound, typically resulting in surface cracking of the rubber material. As oxidation involves the transfer of electrons, reduction in the physical strength of elastomers may also occur from exposure to the oxidizing agent
O.D. (Outer Diameter)
The outermost (largest diameter) surface of a circular object, such as a shaft or a round seal. the term O.D. is frequently used to indicate both the circumferential surface itself as well as the measured diameter of that surface
PA
Polyamide (nylon)
Packing
The filling of the mold cavity or cavities as full as possible without causing undue stress on the molds or causing flash to appear on the finished parts
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