Round cord rings are often used in cases where no suitable O-ring forms are available and the small number of pieces means that tool manufacture is not cost-effective.
In contrast to form-vulcanized O-rings, round cord rings are assembled from extruded cord to any inside diameter by gluing or impact vulcanization. In recent years, however, gluing has been largely discontinued, as the round cord, butt-jointed DIN 7715, has become increasingly popular due to better physical values, among other things. However, the vulcanization point also has lower mechanical properties than the extruded cord. Round cord rings should therefore not be used for dynamic seals, vacuum and gaseous media. For the cord diameter, the dimensional deviation according to Din 7715 Part 3, Class E2, or ± 0.8 percent for the circumferences applies. The O-ring tolerances are not applicable.
