Design Considerations

- physical, mechanical and chemical considerations for Seal and gasket design

There are multiple considerations that must be taken into account when designing a seal or gasket, and Lauren Manufacturing can help lead you through this process.  A few of the first considerations are listed below, but for a more in-depth analysis of what physical, mechanical and chemical characteristics your part requires, call us at 800.683.0676 or send an e-mail.

Step One: Choosing the optimal material

Material Matching  

Environmental factors surrounding your rubber part will greatly influence your choice of material.  Answering the following questions will help narrow down your material selection: 

• Will the material be required to stand up against UV and ozone exposure?
• Are there solvents or other chemicals present?
• Will there be hot or cold temperatures present?
• Is it a static or dynamic sealing application?

Sponge or Dense

Choosing a sponge or dense material depends upon the physical characteristics and attributes needed in the application.  In determining if you need a sponge or dense material, you should consider the following questions:

• Does the application require a very low closing force, such as a door seal on a consumer-type product?
• Does the application require a great deal of interference between the two surfaces, such as the bolting together of two components in an industrial setting?

Step Two: Cross-sectional Design

Several things need to be known about the application before you can properly determine what a good cross-sectional design will be.

• How will the seal be attached to the substrate?
• What is the required size of the cross-section?
• What size of gap or opening must the seal fill and protect?
• What are the tolerances of the enclosure and sealing material?
• What is the amount of closing force that will be tolerated in the application?
• In what direction will the load be applied to the seal?

Note: Determining the direction in which the load is applied to the seal is an important factor.  Very different results will occur if a 60° load is applied as opposed to a 90° load.  Lauren can work with you to help reduce and control the total amount of load required to get a good seal in the following ways:

• The shape of the cross section can be changed, depending on how the load is applied.
• Holes or hollow sections can be introduced into the cross-section to help reduce the load required to compress the seal.

To help you define the tolerance required for your part, The Rubber Manufacturers Association has issued standard dimensional tolerances -- Click here for RMA Tolerance Tables.

Step Three: Attachment

There are multiple ways to attach a seal or gasket.  Lauren can help you determine the optimal way to attach your part based on the application, environment and material.  Consider the following questions to narrow your custom needs:

• Will the seal need to be compression fit into a channel?
• Is a mechanical attachment, i.e. staples, nails, clips, the only way to attach the seal?
• Will the seal function better with an adhesive attachment applied to the seal?

Compression Fit

When desiging compression fit applications, it is critical to meet the required amount of seal compression.  For solid sections, the general effective compression range of 2% to 10% is required to hold the seal in the channel, while sponge seals require 15% to 25% compression to remain effective.  As in many cases, this basic rule of thumb is somewhat dependent on the application, such as the size of the channel itself and the direction from which the load is applied.

Adhesive Attachment Application

• Attachment surfaces should be wider than 1/8" to ensure secure adhesion.
• Adhesive placement should be on flat surfaces on both the seal and the substrate.
• For dynamic sealing situations, the strip of adhesive should be at least 2/3 the width of the cross section for seals up to 1" wide.
• For static situations, adhesive is only needed to hold the seal in place until mating substrates are joined.
• For applications that bend around radii, transfer adhesives generally perform better than supported adhesives (adhesives which use a carrier).
• Supported adhesives help prevent stretching of a seal during application better than transfer adhesives.
• The thickness of the PSA itself should be taken into consideration when determining the overall height of the profile.

(For an explanation of pressure sensitive adhesive attachment systems refer to the section in this guide on Pressure Sensitive Adhesives.)

Mechanical Seal Attachment

When designing seals to be attached mechanically, accommodation must be made for the insertion of the attachment device (clip, nail, staple).  The attachment device either has to fit into the seal itself, or holes must be drilled in the seal.  The seal design has to be such that the mechanical attachment device does not interfere with the compression of the seal.