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By Josh Dunahoe | Jan 24, 2019
GMN fabricates custom silicone foam gasket

A US-based customer of GMN was designing an electrical connection between two plastic housings for an outdoor application. In order to establish the connection, it was vital to achieve a permanent, air-tight seal between the two housings. Given the nature of the design, even the slightest ingress of moisture or foreign particles would hinder the optimal performance and durability of the product. Hence, shielding the seal from dust and water was critical. Additionally, the seal also needed protection from extreme temperatures and flames.   

Originally, the customer utilized a bead of silicone (silicone rubber paste) on the edges of the two housings that hardened over time to form a seal. However, this approach presented several manufacturing challenges and shortcomings. Dispensing a uniform layer of silicone rubber was not only cumbersome, but also inconsistent, leading to an uneven bond line. As the paste became rigid upon drying, it formed a seal that was susceptible to breaking under stress, thereby producing cracks and weakening the bond strength. The drying and curing of the silicone rubber paste also spiked up the processing time, creating a bottleneck on the assembly line.

The customer approached GMN to achieve a better form-fitting solution to prevent moisture ingress. After learning about the environmental conditions that the seal was required to withstand, GMN proposed a custom-fit Roger’s BISCO® silicone foam gasket. From the extensive range of BISCO® silicones available in the market, GMN narrowed it down to HT-800 family to strike the right balance between seal-ability and compressibility. As a Preferred Converter of Rogers Corporation, GMN delivered a high-performance solution with accelerated lead time and competitive pricing.

Roger’s BISCO® silicone, with its high flame resistance, seamlessly fit the needs of the project. In addition to excellent viscoelasticity, it provided high dimensional stability and sealing capability. Contrary to the previous solution, BISCO® silicone foam does not break under stress or pressure. It allowed for quick and easy application, eliminating the extra processing time associated with bead of silicone.

Although, selecting the right material wasn’t enough. Creating a custom shaped gasket to fit the exact configurations of the housings was equally important. Since the customer had initially planned to utilize silicone paste, they did not have the dimensions of the housings readily available. Based on the customer’s sketch and 3D file of the housings, GMN developed a CAD file for the laser tool to fabricate the gasket. By flowing into every nook and cranny of the surface area, the gasket flawlessly married the two housings together to achieve an enhanced seal.

With the help of GMN’s dedicated rapid prototyping team and equipment, we then created two distinct prototypes of custom BISCO® silicone foam HT-800 gaskets in two different thicknesses and durometers. It enabled the customer to test compression and seal strength of the two different gaskets and choose the most optimal solution.

GMN’s ability to determine and source the right material and create a tailored-fit gasket allowed the customer to meet the functional requirements of the project without compromising on the aesthetics. Given our extensive experience and technical expertise with die-cut components, customers can truly rely on GMN to efficiently provide quick design fixes and improvements.