Splicing is when two ends of material are joined together to create a continuous part. These materials are usually supplied in a coil, roll, or strip. Splicing is often used to fabricate rubber O-Rings from a cut to length cord or a frame from four different segments of material. Splicing can be used in many different parts from simple, low-cost solutions to very complex, highly engineered solutions.
When it comes time to choose a splicing technique for a rubber gasket, there are a couple important decisions that the engineer must make. By balancing costs against capabilities, you can find the solution that works best. The main technical challenges that the engineer must address before splicing are the following:
- Splice Configuration – The shape of the two adjoining ends.
- Splice Bond System – They type of adhesion that will be used to hold the two ends together.
The type of cut/angle for the joining ends of the material is the first decision that needs to be made. Here we will discuss the four most common type of splicing methods and how they are used in gasket production. With multiple technique options, it is important to know how each will perform under different pressures and configurations.
- Butt Splice – This type of splice is when two ends of the strip or cord of material are flattened, cut at a 90-degree angle, and bonded end to end. This type of splice is commonly used for gaskets that are exposed to little or no stress at the point of the splice.
- Bevel Splice – With this method, the two ends of the strip of material are typically cut at a 45-degree angle and bonded end to end. Using a 45-degree angle allows for a larger surface area to be used in the bonding process vs. the 90-degree angle butt splice. Allowing for additional surface area increases the level of bonding strength.
- Step Splices – When it comes to bonding strength, the step splice method is superior. It is stronger than both butt and bevel splices. By including a step like cut in the ends of the material, this will produce the most surface area for the bond. Gaskets that are bonded with a step splice may deform under pressure or stress of the application, but it is unlikely that the two ends will separate. The step splice is considered to be the strongest splice option.
- Corner Splice – Finally, there is the corner splice. This cut is like the bevel splice but it more common in a frame like design. Though it is not as common as the other 3 mentioned techniques, certain vulcanized gaskets are designed with a corner splice. A corner splice may be used for sealing applications where the gasket is exposed to minimal pressure or stress.
Splice Bond System
Now that the ends of the material have been cut using the appropriate method, it is time to choose which type of bonding system will best keep the two ends fastened together. This decision typically depends on the complexity of the forces and stress on the rubber and the design of the part. Below are the most common bonding options.
- Hot Splicing – Hot splicing uses heat, pressure, and a film or uncured rubber to join the two ends. Hot splicing uses a thin polyethylene (PE) film followed by either a conventional heating source or infrared (IR) light. Using traditional heating sources takes longer than IR bonding, but both methods can create strong, reliable adhesions. Also, the type of sponge or solid rubber being used often determines whether conventional heat or IR is recommended. Some materials, such as silicone, support traditional hot splicing but not IR. The shape and size of the ends are important considerations, too.
- Vulcanization – Like hot splicing, vulcanization uses an uncured rubber compound, along with heat and pressure. Both hot splicing and vulcanization create chemical bonds at the molecular level. Compared to hot splicing, vulcanizing is more forgiving since it does not require a smooth and precise cut. With vulcanization, an uncured rubber compound flows into gaps and fills any space while forming a strong bond between the end surfaces. Once the two ends are joined together, the bond is placed in a hot mold. Cooling is required to complete the process.
- Cold Splicing – In this method, the two ends are bonded together by gluing two or more pieces of a rubber cord or strip together using a quick-setting glue. With using a type of glue instead of a rubber compound, it is important to note that the part will have different material properties at the joint than the rest of the material being used. Generally, depending on the complexity of the part, cold splicing will be less expensive.
For real examples of splicing being used in an application, read our case study on how PGC used splicing methods to produce seal for a Navy aircraft carrier ship deck.
If you have any questions or want more information on how splicing may be a part of the solution for your next application, contact a PGC engineer.