Spliced and vulcanized o-rings are made from extruded cord stock that has been cut and bonded together, as opposed to molded o-rings; those that have been compression or injection molded as one piece. Vulcanized o-rings are an excellent choice for static sealing applications when molded o-rings cannot be used due to large or non-standard dimensions, when only a few pieces are needed, or when you need an o-ring right away and cannot wait the standard lead time for molded production. Vulcanized o-rings can be made from a range of elastomers and in virtually any size.
To make a vulcanized o-ring, continuous length cord is cut to length and then joined together. A bonding agent is applied to the ends which are then joined together in a mold at a high temperature for a specified period of time. This process forms the molecular bond necessary to create a strong joint.
Advantages and Limitations of Spliced & Vulcanized O-Rings
Vulcanized o-rings are a good choice for static sealing applications, or ones where the o-ring does not come in contact with moving parts. They are not recommended in dynamic applications, where the o-ring is subjected to the stress of moving parts. Vulcanized o-rings also may not be a good choice for those who need very large quantities of o-rings. In this case, it could be more cost effective to create tooling and buy custom molded o-rings.
Different Options for Spliced & Vulcanized O-Rings
There are several key characteristics that define any vulcanized o-ring:
- Material – type of rubber, color, durometer
- Cross Section (CS) – thickness of the cord
- Cut Length (CL) – calculated based on the desired diameter of the o-ring. See below.
- Cut Angle:
- Butt Cut (default) – 90 degree cut where the cord is cut straight from top to bottom.
- Skive Cut (additional charge) – 45 degree angle cut, also called a bevel cut. This cut is used in order to have more of the material’s surface area in contact at the joint to make it stronger.
How to Calculate Cut Length
Since an o-ring is a circular shape, you must calculate the circumference, or the length of cord needed to form the o-ring with the desired diameter. Some commonly used terms for vulcanized o-rings include:
- CL = Cut Length
- ID = Inside Diameter
- OD = Outside Diameter
- MD = Mean Diameter
- π ≈ 3.1416 (rounded to 4 decimals to simplify calculations)
The formula for calculating the Cut Length (CL) for a vulcanized o-ring depends on your known dimensions:
ID and CS are known: CL = (ID + CS) * π
ID and OD are known: CL = ((ID + OD) / 2) * π
MD is known: CL = MD * π
Our Commitment to Quality
Global O-Ring always inspects 100% of the vulcanized o-rings that we ship to our customers. This includes inspection of the joint to make sure there are no pinholes, breaks, or any flash (excess material). If any of these are present, we will either scrap or re-work the o-rings before shipping. This rigorous inspection process helps ensure consistent quality for all of our vulcanized o-rings.