![]() At lower amounts of compression the X profile acts more like an oring. It is evident that the amount of force needed to compress the round cross section is significantly less than both the flat and X profiles. Below is the plot showing force per linear inch of seal versus percent compression. The molded parts were then compressed between parallel platens in a universal testing machine. The round, square, and X profiles were molded based on the AS568-010 oring using a standard 75 durometer fluorocarbon, 01VT7EE. Experience and testing have shown that round cross sections generally offer the best compromise between contact area and compressive force. Excessive compressive forces can bow housings, break fasteners, and make assembly cumbersome. Oftentimes designs require functional seals to compress with minimum force. The edges of the contact are a highlighted in red.Ī designer will generally choose the largest contact area possible, but must also consider the compressive force needed activate the seal. Also shown below are views of the contact width taken using a transparent top to the compression fixture. The round cross section seal contacts 0.038” of the mating surface, the square cross section contacts 0.070”, and the X cross section contacts 0.022” twice, one for each lobe. The contact area must be wider than the imperfection to form a seal.īelow are profiles of the three cross sections discussed. The width of the contact area can be critical if the seal needs to bridge surface imperfections such as machine marks, scratches, porosity, or sinks on the mating surfaces. ![]() The width of the contact between the seal and the mating surface can vary greatly, as can the forces needed to compress the seals. When each profile is compressed it contacts the mating surfaces differently. The piece cost is also generally more because the molding process is more involved. Generally the molds are more intricate and expensive so the up-front costs are higher. The disadvantage of this profile is its higher cost. X-Ring gaskets are popular in reciprocating applications where they can reduce friction. A disadvantage of the rectangular profile is that significantly more force is needed to compress it. The rectangular cross section lends itself to die and laser cutting making prototyping simple, quick, and easy. ![]() Rectangular profile gaskets have the ability to bridge large surface imperfections because their entire width is in contact with the mating surface. Die cutting and laser cutting are not possible. One disadvantage of the round cross section is that gaskets and seals must be either molded or extruded. The lower compressive force needed to compress the seal can minimize deflection of mating housings. The higher point load is advantageous because it creates a better seal between the bulk elastomer and the mating surface. The round profile of this seal creates a higher point load (stress) with a lower compressive force. Round cross section gaskets and seals are in very common usage. Each gasket profile has advantages and disadvantages: ![]()
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