Enclosure gaskets for environmental sealing can be made of made of hollow extrusions, sponge profiles, molded shapes, or solid O-rings. Enclosure designers have a choice of sealing solutions, but hollow gaskets support greater compression and more forgiving enclosure tolerances. Hollow enclosure seals also support cost-effective fabrication and the use of pressure-sensitive adhesives (PSA) for ease-of-installation. As this article explains, engineers who choose the right rubber products can strengthen their enclosure designs.
Hollow Seals vs. Solid Seals
Compared to solid seals, hollow seals can handle significantly more compression (up to about 50%) with lower closure force. Plus, solid seals may have irregular or inconsistent gaps if the enclosure’s tolerances aren’t tight enough. The causes of these irregularities include weak or thin enclosure materials and variations in the thickness of the door, hatch, or lid. In addition, the lightweight fasteners used with thinner enclosure materials may not be able to handle the large loads needed for a solid rubber seal.
The problem with irregular gaps in an enclosure seal is that they cause inconsistent compression forces along the gasket’s perimeter. In turn, this causes leaking. Engineers can redesign an enclosure’s dimensions to support tighter tolerances, but this adds costs and complexity to projects. Also, it’s important to remember that the tolerances for rubber products aren’t as tight as the tolerances for sheet metal, a common enclosure material. In other words, you can’t design rubber parts just like metal ones.
Flat Panel Seals and Attachment Methods for Enclosure Gaskets
Larger enclosure gaskets are more susceptible to leaking because the larger seal perimeter increases the likelihood that there are gap variations. Plus, larger enclosures may lack the space for a groove and require sealing between the flat surfaces of the door, lid, or hatch and the enclosure itself. Flat panel gaskets, hollow extrusions that are cut-to-size with water jet equipment and then hot spliced into finished gaskets, are a good choice for sealing these larger enclosures, many of which are made of thin metal or plastic.
When designing flat panel seals, engineers need to ensure that these hollow gaskets can be attached securely. PSA tapes can be applied to extrusions with D, P, or rectangular shapes. They can’t bend around radiused corners, however, and require multiple-angled spliced corners instead of single 90° butt splice. Fasteners such as bolts or screws are also used to secure enclosure gaskets, typically hollow seals with P and double P cross-sections. Unlike PSA tapes, fasteners require hand tools like drills.
Solid Rubber vs. Sponge Rubber
Some engineers choose sponge profiles instead of hollow extrusions for sealing with low closure forces. The problem with sponge rubber, however, is compression set – the permanent deformation of an enclosure gasket material when a compressive stress is removed. When sponge door seals are left closed for a long period of time, they may not return to their original thickness after the door is opened. This inability to “rebound” prevents the formation of a secure seal when the door is closed again.
Sponge profiles also have less abrasion resistance than hollow extrusions that are made of solid rubber. As a result, sponge door seals are more susceptible to abrasion when doors are opened and closed repeatedly. Over time, this wearing away of gasket materials can create gaps that cause leaking. Sponge rubber is also susceptible to soaking up fluids that an enclosure seal needs to exclude. For example, a sponge enclosure seal that’s subjected to a heavy rainstorm may have cells that fill with water.
Custom Enclosure Gaskets from Elasto Proxy
Do you need custom enclosure gaskets for environmental sealing? Whether you’re designing a lighting fixture, a toolbox, an electronic enclosure, or the door for a mobile equipment cabin, Elasto Proxy offers design assistance, help with material selection, expert fabrication, and value-added manufacturing services. To discuss your sealing application with one of our solutions providers, please contact us.